To see the other types of publications on this topic, follow the link: Abalones.
Dissertations / Theses on the topic 'Abalones'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Abalones.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Jackson, Daniel John. "Applied and molecular approaches to improving the cultivation of the tropical abalone Haliotis asinina Linnaeus /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17413.pdf.
Full text
2
Gray, Michael. "Morphometrics and reproduction of Terebrasabella heterouncinata (Polychaeta:Sabellidae), infesting abalone (Haliotis midae) from different culture environments." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1018231.
Full textAbstract:
In the late 1980's abalone culturalists noticed reduced growth rate and shell deformities in some abalone stocks. These problems were the result of infestations by a shell boring polychaete, Terebrasabella heterouncinata. Under intensive abalone culture conditions the level of infestation can reach epidemic proportions and there are often severe consequences for the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. This study formed part of an ongoing project that is aimed at investigating the basic biology of Terebrasabella heterouncinata. The majority of abalone farmers in South Africa feed their abalone either naturally occurring kelp (Ecklonia maxima) or the formulated abalone feed, Abfeed. Farmers have suggested that the use of Abfeed is associated with higher sabellid infestation levels and changing the abalone diet from Abfeed to kelp helps reduce sabellid infestation. Speculation has arisen indicating that older, slower growing abalone are more susceptible to sabellid infestation. The effect of host abalone diet history and their growth on sabellid settlement success, morphometries and reproduction was quantified. To better understand the plasticity of the expression of life history traits the variability of morphometric and reproductive characteristics was compared between different farm environments. And more...
3
Lambrechts, Daneel. "Molecular analysis of genetic variation and relationships amongst abalone (Haliotis midae) at the I&J abalone hatchery at Danger Point, Gansbaai, R.S.A." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52943.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: The species Haliotis midae is the only abalone species of commercial importance to the South African fisheries industry. The species is currently under substantial pressure due to commercial harvest and illegal poaching, to the extent that genetic and biodiversity may be under threat. The species is also being cultured in commercial systems for supply to international markets. The South African production for 2002 amounted to 350 tons. The commercial production of abalone may also have implications with regard to genetic diversity of natural and commercial populations. The aim of this project was to assess the genetic diversity of the natural and commercial populations of abalone at the I&J Abalone Farm, Danger Point, Gansbaai, in South Africa, in order to make recommendation with regard to possible impact on natural diversity as well as internal management systems. Distortion of natural genetic diversity or a loss of internal diversity will have detrimental consequences. Representative samples have been obtained from the surrounding natural population, as well as the commercial populations, including the broodstock and various progeny groups. Both mtDNA and AFLP molecular techniques were used to assess genetic diversity. Data analysis showed that the genetic profile of the commercial population display sufficient genetic variation. The genetic structure of the commercial population also displays no significant deviation from that of the surrounding natural population, i.e. the population of origin. The results through give indication of a small, though unsignificant loss of genetic variation from the broodstock to the subsequent progeny groups. The investigation conclude that the commercial populations of abalone at the I&J Abalone Farm, Danger Point, Gansbaai, in its current format holds no threat to the disruption of the genetic diversity of the surrounding natural population. Further, the commercial population possesses sufficient genetic variation in view of future genetic development. There is signs of a slight loss of genetic variation in the change over from the broodstock to the progeny groups. This would necessitate careful and controlled replacement of the original broodstock with new animals from the commercial progeny groups as part of an ongoing process of domestication.
AFRIKAANSE OPSOMMING: Die spesie Haliotis midae is die enigste perlemoen spesie van kommersiële belang vir Suid Afrikaanse visserye. Die spesie verkeer tans onder toenemende druk as gevolg van kommersiële en onwettige vangste, tot so 'n mate dat genetiese en biodiversiteit daardeur geaffekteer kan word. Die spesie word in toenemende mate kunsmatig gekweek vir voorsiening aan internasionale markte. Suid Afrikaanse produksie vir 2002 beloop reeds sowat 350 ton per jaar. Die kunsmatige produksie van perlemoen het ook moontlike implikasies op die genetiese diversiteit van natuurlike en kommersiële populasies van die perlemoen, Haliotis midae. Die doel van die projek was om die aard van genetiese diversiteit van die natuurlike en kommersiële populasies van perlemoen by die I&J Perlemoen Plaas, Danger Point, Gansbaai in Suid Afrika te ondersoek, ten einde aanbevelings te maak ten opsigte van moontlike impak op natuurlike diversiteit asook ten opsigte van interne genetiese bestuurstelsels. Versteuring van natuurlike diversiteit of verlies van interne diversiteit hou nadelige gevolge in. Verteenwoordigende monsters is versamel vanuit die omliggende natuurlike populasies, sowel as van die kommersiële populasie op die plaas, insluitend die teelmateriaal en verskillende nageslaggroepe. Beide mtDNA en AFLP-molekulêre tegnieke is gebruik tydens die ontleding van genetiese diversiteit. Dataontleding het aangetoon dat die genetiese profiel van die kommersiële populasie voldoende genetiese variasie demonstreer. Die genetiese struktuur van die kommersiële populasie toon verder geen betekenisvolle verskil met die omliggende natuurlike populasie nie, dit wil sê met die populasie van oorsprong nie. Die resultate toon verder 'n geringe, dog nie betekenisvolle verlies van genetiese variasie wat waargeneem word met oorgang van die teelmateriaal na die onderskeie nageslaggroepe. Die bevindinge van die ondersoek is dus dat die kommersiële populasie op die I&J Perlemoen Plaas, Danger Point, Gansbaai, in die huidige formaat, geen bedreiging inhou vir die versteuring van die omliggende natuurlike genetiese diversiteit nie. Verdere bevindinge is dat die kommersiële populasie oor voldoende genetiese diversiteit beskik met die oog op toekomstige genetiese ontwikkeling. Daar is tekens van 'n geringe afname in genetiese diversiteit met die oorgang vanaf die teelmateriaal na die nageslaggroepe. Dit beklemtoon die belang van 'n gekontroleerde vervanging van die oorspronklike teelmateriaal met nuwe teeldiere vanuit die kommersiële populasie as deel van die domestikasieproses.
4
Britz, P. J. (Peter Jacobus) 1959. "The nutritional requirements of Haliotis midae and development of a practical diet for abalone aquaculture." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005152.
Full textAbstract:
The available literature on abalone nutrition was synthesised and the prospects for developing a complete pelleted dry feed for Haliotis midae evaluated. The similar body compositions, digestive structures, enzyme activity, acceptance of a wide variety of feed ingredients and comparable growth performance on formulated diets of various abalone species suggests that they have similar nutritional requirements. Abalone also appear to be similar to other farmed monogastric animals in that digestion is primarily extracelluar and they possess a large, muscular crop and stomach. Abalone energy metabolism is carbohydrate based. They are capable of digesting high levels of dietary protein but their ability to utilise fat is limited. Abalone have been shown to consume predictable amounts of dry feed which is efficiently converted into body weight. Efficiency indices of utilisation of formulated feeds, such as feed conversion ratio, protein efficiency ratio, net protein utilisation and apparent digestibility have been successfully applied to abalone. It was concluded that the prospects for developing complete diets for H. midae using a conventional animal feed science model were good. The ability of H. midae to utilise a range of proteins which had potential for inclusion in practical diets was investigated. Five protein rich ingredients, namely, casein, fishmeal, soya oil cake, Spirulina, and torula yeast, were fed to H. midae in semi-purified diets. Two algal diets, fresh Plocamium corallorhiza and dried Ecklonia maxima were fed as controls. Abalone fed on fishmeal and Spirulina based diets displayed significantly higher growth rates than diets containing soya oil cake, torula yeast, casein and E. maxima. Growth rates of abalone fed with P. corallorhiza were significantly lower than all other diets. All artificial diets yield lower feed conversion ratios (0.7-1.8) and higher protein efficiency ratios (3.3-6.5) ratios than the seaweed control diets (FCR = 2.8-3.4; PER = 2.2-3.0). The results indicated that fishmeal and Spirulina were the most suitable proteins for inclusion in practical diets for H. midae. The effect of protein level on growth rate and nutritional indices was evaluated by feeding starch bound, fishmeal based diets containing 27, 32, 37, 42 and 47% protein to juvenile H. midae. Weight gain was positively related to the level of dietary protein, increasing by 18% between 27% and 47% protein. Protein efficiency ratio declining from 3.2 to 2.3 with an increasing dietary protein content. Feed consumption rate was approximately 1% of body weight per day for all diets. Post-weaning abalone (ca. lOmm shell length, 0.2g) differed from larger juveniles (ca. 35mm, 8g) in their response to varying proportions of dietary protein and energy. The smaller animals appeared to have a lower protein requirement and poorer ability to utilise lipid than the larger juveniles. Proximate analyses revealed that the levels of protein, lipid and carbohydrate in abalone soft tissue increased with increasing dietary levels of these nutrients. Larger juveniles contained significantly higher levels of protein and carbohydrate, but lower levels of lipid, ash and moisture, than the smaller post-weaning abalone. The assimilation efficiency of [U-¹⁴C]-arginine by H. midae fed diets enriched with [U-¹⁴C]-arginine was only 0.45%. Furthennore, supplementation of diets with graded levels of crystalline arginine did not have any effect on growth rates. It was concluded that the prospects for defining the quantitative amino acid requirements of H. midae using crystalline amino acids are not promising. Rates of gastric evacuation and enzyme secretion were monitored in juvenile H. midae fed an extruded, fishmeal based dry feed. Gut fullness peaked 6h after feed was offered and the bulk of feed consumed was digested within 24 h. Enzyme secretion appeared to begin with the onset of feeding and continued for at least 6h after peak gut fullness was attained. Protease activity increased significantly following ingestion but amylase activity was maintained at a more or less constant level. A low level of lipase activity was observed suggesting that the ability of H. midae to digest fat is limited. The growth rate of H. midae fed an extruded, fishmeal based feed increased with increasing temperature between 12°C and 20°C. Between 20°C and 24°C a marked decline in growth rate accompanied by a deterioration in feed conversion and increased mortality was observed. Consumption of a dry pelleted feed was shown to be a function of body size and temperature. Based on these data a model which predicts a daily ration for H. midae was developed. The present study showed that H. midae efficiently utilises extruded dry feeds containing conventional feed ingredients. Although technical difficulties were encountered in measuring apparent digestibility, it was concluded that the prospects for developing practical diets according to established nutritional principles are promising.
5
Lyon, Robert Gary. "Aspects of the physiology of the South African abalone, Haliotis Midae L., and implications for intensive abalone culture." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005069.
Full textAbstract:
A physiological study was carried out to determine the effects of temperature, quantity of food fed, feeding activity and size class on the oxygen consumption and ammonia production of the South African abalone Haliotis midae L.. A set of intermittent flow respirometer chambers were used in a recirculating system to measure the oxygen consumption rates of fed (postprandial) and unfed (postabsorptive) abalone for three different size classes (15, 30, and 50mm) at three different temperatures (16°, 20° and 23°C) over a 24 hour period. Ammonia production rates and food consumption rates were simultaneously determined. Oxygen consumption and Ammonia production rates per gram abalone were linear functions of abalone size, temperature, and mass of food consumed. Oxygen consumption and ammonia production rates were found to increase proportionally to temperature and in inverse proportion to abalone size. These rates were significantly higher for fed as opposed to unfed abalone. Equations were derived to predict oxygen consumption and ammonia production for fed and unfed animals for a range of temperatures and size classes of abalone. A 96h LC50 lethal toxicity test for exposure to ammonia established 1.08mg.1⁻¹ of unionised ammonia as the lethal limit. A test on the long term effects on growth of acute exposure (12h) to various sublethal concentrations of ammonia showed no significant effects on growth for concentrations below 0.88 mg.1⁻¹. A safe chronic exposure level of 0.02 mg.1¹ NH₃-N was used to predict optimal flow rates required per kilogram of abalone in a rearing tank over a range of size classes and temperatures. The physiological and biological requirements of H. midae and the implications of this knowledge for rearing tank management and optimal design are discussed.
6
Green, Alistair John. "The protein and energy requirements of the South African abalone, Haliotis midae." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1008261.
Full textAbstract:
The abalone (Haliotis midae) culture industry in South Africa is becoming increasingly dependent on the use of formulated feeds, due to limitations in the supply of kelp. The bulk of the feeds that are currently available were developed based on the requirements of juvenile abalone cultured within the optimal temperature range for growth (18 - 20 °C). However, most abalone farming facilities are land-based pump ashore operations and are thus mostly exposed to temperatures outside of this range. In addition, these feeds have been found to be unsuitable for abalone cultured at elevated water temperatures (> 20°C). The aim of the study was to develop size and temperature specific diets for H midoe through optimisation of dietary protein, energy and lipid levels. Abalone were cultured under farm-like conditions in three partially recirculating temperature controlled systems at either 18, 22 or 24°C and fed formulated diets containing graded levels of protein (18,22 and 26 %) and energy (11.6, 13.5 and 16.2 MJ.kg·I ). Abalone were stocked into baskets at 5 % of available of surface area (n=36) and each diet (n=9) was fed to four baskets of abalone at each of the three temperature regimes for ten weeks. Abalone growth was temperature dependent, with growth declining from 4.33 g.month-I for abalone cultured at 18°C to 0.77 g.month-I at 24°C. Dietary protein could be reduced from 26 to 18 % provided dietary energy levels were maintained at 13.5 MJ.kg- l • A dietary energy level of 11.6 MJ.kg-1 was insufficient to meet the energetic requirements of H midae regardless of the protein content of the diet. The effects of water temperature and body size on the protein requirements of H midae were investigated by culturing abalone at temperatures within the optimal range for abalone farming (i.e. 14, 16 and 18°C). Three size classes of abalone (15, 50 and 80 mm) were fed formulated feed containing graded levels of dietary protein (20, 26, 32, 38 and 44 %) under controlled laboratory conditions for 12 weeks, and, in a separate experiment, under commercial farm conditions for 24 weeks. It was not possible to convincingly define the optimal protein levels for abalone of different sizes in this experiment because growth rates fell below average commercial growth rates obtained on farms. Growth was temperature dependent in the laboratory trial, with the rate of weight gain of the 15 mm (ANOV A: p=0.002) and 50 mm abalone (ANOV A: p=0.02) increasing significantly with an increase in temperature from 14 to 18°C. In the farm trial, dietary protein content did not affect the growth rate of the 10-15 or 80 mm abalone (ANOVA: p>0.05), however, the 50 mm abalone displayed significantly higher weight gain on the 32 % (4.72±0.20 g.month-I ) and 38 % (5.01±0.34 g.month-I ) protein diets compared to those fed the 20 % protein diet (3.75±0.13 g.month-I ) (ANOVA: p=O.OI). Although definition of optimal dietary protein levels were not possible, the effects of dietary protein content and water temperature on the growth of H midae were independent signifying that the protein requirements of abalone are temperature independent. In addition, there was no evidence to indicate that abalone of the different sizes tested here had different dietary protein requirements. The size specific dietary lipid and protein requirements of H midae were investigated by feeding two size classes of abalone (30 and 60 mm initial shell length) diets containing graded levels of dietary lipid (4, 7, 10, 13 and 16 %) and protein (34 - 39 %) for 12 weeks. The 30 and 60 mm abalone were stocked at 7 (n=200) and 9 % (n=36) of the available basket surface area respectively and each diet was fed to four baskets of abalone of each size class. The protein requirements of H. midae are influenced by the amount of available dietary energy and thus it is possible that the ability of abalone to utilise lipids as a source of energy differs in the presence of varying levels of dietary protein. High levels of dietary lipid negatively affected the growth, condition factor and soft tissue glycogen content of both size classes of abalone. This negative effect was greater in the 30 mm size class compared to the 60 mm abalone. The corresponding increase in feed consumption and feed conversion ratio in response to increasing levels of dietary protein also provides evidence that abalone are unable to utilise dietary lipids as an energy source and high levels of dietary lipid probably inhibit the uptake of carbohydrates and protein. High dietary lipid levels did however appear to promote gonad maturation. It was possible to reduce dietary protein from 34 to 20 % without negatively affecting growth through the maintenance of dietary energy levels and thus it is recommended that future experiments on the energy content of formulated feeds should focus on the improved use of carbohydrates. Reductions in the protein portion of formulated feeds for H. midae are possible provided the diet contains sufficient levels of energy supplied from carbohydrates. As the ability of abalone to utilise dietary lipid is limited, lipids are unlikely to play a significant role as an energy source in abalone feeds. Further investigations should focus on the utilisation of various carbohydrate sources in abalone feeds.
7
De, Beer Mathilde. "Induction of triploidy in the South African abalone, Haliotis midae, by the use of hydrostatic pressure." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16299.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The indigenous abalone, Haliotis midae has been a successfully cultured aquaculture species in South Africa since 1990. It has a slow growth rate and takes from two to five years to reach market size. Like for most other commercially important abalone species, the slow growth rate of H. midae is a cause of concern with regard to the profitability of farming and global competitiveness of the species. Ploidy manipulation of the maternal genome, a universally growing practice in shellfish culture, is considered a promising method to improve the growth rate of abalone - a desirable trait in aquaculture organisms from a commercial perspective. This manipulation technique is employed to achieve sterility, which results in limited gonad development. The consequent re-allocation of resources to somatic growth results in improved growth. The purpose of this study was to establish a viable method for the induction and validation of triploidy, on a commercial scale, in the South African abalone, H. midae. The focus was on hydrostatic pressure as a method of induction and flow cytometry as the method of validation. The results obtained confirm hydrostatic pressure as an effective method for the induction of triploidy in H. midae, delivering high percentages of triploidy (>80%) over a wide range of pressures and times, in 48 hour-old larvae. Hydrostatic pressure had a negative effect on survival in 20 hour-old larvae. Flow cytometry was validated as a reliable, fast and accurate, though expensive, method for identification of triploidy in H. midae. As an outcome of this study a manual of “Procedures for the Induction and Validation of Triploidy in the abalone” is presented (Appendix 1) together with recommendations for further studies on triploidy in the South African abalone, H. midae.
AFRIKAANSE OPSOMMING: Die inheemse perlemoen, Haliotis midae, is sedert 1990 ‘n suksesvol gekweekte akwakultuur spesie in Suid-Afrika. ‘n Kenmerk van die spesie is die stadige groeitempo van tussen twee en vyf jaar ten einde bemarkbare grootte te bereik. Soos vir die meerderheid perlemoen van kommersiële belang, is hierdie stadige groeitempo rede tot kommer met betrekking tot die winsgewende kweek en wêreldwye mededingendheid van die spesie. Die manipulasie van ploïdie van die moederlike genoom is ‘n toenemende praktyk in skulpvisboerdery en word gereken as ‘n belowende metode om die groeitempo van perlemoen te verbeter. Hierdie manipulasietegniek word gebruik om steriliteit te verkry wat manifesteer as onderdrukte ontwikkeling van die geslagsklier. Die gevolg is die herkanalisering van bronne na somatiese groei. Die doel van hierdie studie was om ‘n lewensvatbare metode vir die induksie van triploïdie op ‘n kommersiële skaal in die Suid-Afrikaanse perlemoen, H. midae, te vestig. Daar is op hidrostatiese druk as metode vir die induksie en vloei-sitometrie as metode vir die geldigverklaring van triploïdie gefokus. Die resultate van hierdie studie bevestig dat hidrostatiese druk ‘n effektiewe metode vir die induksie van triploïdie in H. midae is. Hoë persentasies van triploïdie (>80%) is oor ‘n wye reeks van drukke en tye in 48 uur oue larwes verkry. Daar is gevind dat hidrostatiese drukbehandeling ‘n negatiewe effek op die oorlewing van 20 uur oue larwes het. Vloei-sitometrie is bevestig as ‘n betroubare, vinnig en akkurate, maar duur metode vir die identifikasie van triploïdie in H. midae. As ‘n uitvloeisel van die studie word ‘n handleiding “Procedures for the Induction and Validation of Triploidy in the abalone” (Appendix 1) aangebied tesame met aanbevelings vir verdere studies rakende triploïdie in die Suid-Afrikaanse perlemoen, H. midae.
8
Godfrey, Brian Peter. "The potential of abalone stock enhancement in the Eastern Cape Province of South Africa." Thesis, Connect to this title online, 2003. http://eprints.ru.ac.za/23/.
Full text
9
Swanson, Willie J. "The molecular evolution of abalone fertilization proteins /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907825.
Full text
10
Hancock, Andrew. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery /." Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.
Full text
11
Slabbert, Ruhan. "Molecular analysis of genetic variation and relationships within the population of abalone (Haliotis midae) at the Sea Plant Products abalone hatchery, Hermanus, R.S.A." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50027.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The species Haliotis midae is the only commercially exploitable abalone species of the six found in the South African coastal waters. This species is under substantial pressure from both legal and illegal harvesters, to such an extent that it could be commercially extinct within four years. Efforts to alleviate the pressures on the natural populations of both illegal and legal harvesting are being made. The genetic management systems for abalone farming and ranching activities should be carefully evaluated. The loss of genetic diversity and the risks of contaminating the gene pools of natural populations in the vicinity of a farm should be minimized. Genetic evaluation studies will be at great importance to acquire the necessary data needed for genetic diversity and differentiation analysis. The aim at this study was to develop species-specific microsatellite DNA markers to assess the genetic diversity and differentiation within and between the brood stock and commercial stock of the Sea Plant Products abalone farm (Hermanus, Republic of South Africa) and natural populations related to the brood stock. The species-specific DNA markers were also used for parentage assignments within the tarm population (first for abalone) and preliminary OTL (quantitative trait loci)-discovery analysis studying growth rate segregation. Samples were taken of the farm's brood stock and commercial stock (Rows 2, 3, 4) as well as from two natural populations (Saldanha Bay and Black Rock) related to the brood stock. Various statistical parameters and software packages were used to assess genetic diversity and differentiation, to infer parentage and to look for OTL's. Eight species-specific microsatellite DNA markers were designed and used for data analysis. Data analysis showed a loss at genetic diversity from the brood stock to the commercial stock caused by the subdivision of the original brood stock into rows and the differential contributions of parents to the offspring. No genetic differentiation (Fst) was detected between the farm and natural populations, except for the offspring of Row2. levels of inbreeding (ns) were high for all loci within the populations. Thirty-eight percent of all studied offspring were confidently assigned to a couple. The preliminary QTldiscovery suggested the segregation of a number of alleles and genotypes with growth rate. The study concluded that the commercial abalone population of the Sea Plant Products abalone farm holds no threat to the disruption of the genetic diversity of the natural populations. It is proposed that the farm implement a rotational breeding program to increase the genetic diversity of the commercial population. Any newly acquired brood stock must be profiled before their introduction into the breeding program to assess the influence of the animals on the current levels of genetic diversity within the farm. The accuracy and reliability of parentage assignments and QTl-discovery need to be optimised by adding more loci and sampling more animals or even by trying and developing new methods.
AFRIKAANSE OPSOMMING: Van die ses perlemoen spesies wat langs die Suid-Afrikaanse kus gevind word, is die spesie Haliotis midae die enigste een wat van kommersiële belang is. Wettige, sowel as onwettige versameling, plaas hierdie spesie onder sulke geweldige druk dat dit dalk binne vier jaar verlore kan wees vir die kommersiële bedryf. Verskeie strategieë word tans geïmplimenteer om hierdie druk te verlig. Die genetiese bestuurstrategieë binne perlemoen plase moet deeglik ondersoek word. Die verlies aan genetiese diversiteit en die moontlikheid vir die kontaminering van die natuurlike populasies in die omgewing van die plaas se geenpoel, moet uitgeskakel word. Genetiese evaluasies sal van groot belang wees om die nodige data vir genetiese diversiteit- en differensiasie-analises te verkry. Die doel van die studie was om spesies-spesifieke mikrosatelliet DNA merkers te ontwikkel wat gebruik sou word om die genetiese diversiteit en differensiasie binne en tussen die broei diere en die kommersiële diere van Sea Plant Products se perlemoen plaas (Hermanus, Republiek van Suid- Afrika) en die natuurlike populasies wat verwant is aan die broei diere, te bepaal. Die spesies-spesifieke DNA merkers is ook vir ouerskap-bepalings binne die plaas se populasie gebruik, asook vir voorlopige OTL (quantitative trait locI) - ontdekking met betrekking tot groeitempo segregasie. Monsters van die plaas se broei diere en kommersiële diere (Ry 2, 3, 4) asook van twee natuurlike populasies (Saldanha Baai en Black Rock) wat verwant is aan die broei diere, is geneem. 'n Verskeidenheid van statistiese parameters en sagteware pakette is vir die genetiese diversiteit- en differensiasie-analises, vir ouerskap-bepalings en vir die opspoor van OTL's gebruik. Agt spesies-spesifieke mikrosatelliet DNA merkers is ontwerp en toe gebruik vir die data analises. 'n Verlies aan genetiese diversiteit vanaf die broei diere na die kommersiële diere is deur die data analises uitgewys. Dit is veroorsaak deur die verdeling van die oorspronklike broei diere in rye en die differensiële bydraes deur die ouers na die nageslag. Geen genetiese differensiasie (Fst) is tussen die plaas se populasie en die natuurlike populasies gevind nie, maar die nageslag van Ry 2 het wel differensiasie getoon. Die vlakke van inteling (Fis) was hoog oor alle lokusse binne alle populasies. Agt-en-dertig persent van die nageslag wat bestudeer is, was suksesvol met 'n ouerpaartjie geassosieer. Die voorlopige OTL-ontdekking studie toon die potesiële segregasie van 'n aantal allele en genotipes saam met groeitempo. Die bevindinge van die studie is dat die kommersiële populasie op die Sea Plant Products perlemoen plaas, geen bedreiging vir die versteuring van die natuurlike populasies se genetiese diversiteit inhou nie. Daar is voorgestel dat die plaas 'n rotasie-basis broeiprogram moet implimenteer om sodoende die genetiese diversiteit van die kommersiële populasie te verhoog. Enige nuwe broei diere se genetiese profiel moet ook voor die tyd ondersoek word om te sien wat se effek hierdie diere op die huidige genetiese diversiteit van die kommersiële populasie sal hê. Die akkuraatheid en betroubaarheid van die ouerskap-bepalings en OTL-ontdekking moet optimiseer word deur of meer lokusse te bestudeer, of meer diere in analises te gebruik of selfs om nuwe tegnieke te probeer of te ontwikkel.
12
Knauer, Jens. "Development of an artificial weaning diet for the South African abalone, Haliotis midae (Haliotidae: Gastropoda)." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1004099.
Full textAbstract:
An adequate supply of diatoms during the weaning stage (generally 5 - 10 mm shell length (SL)) is one of the primary constraints to the commercial culture of the South African abalone, Haliotis midae. Because of the seriousness of the problem, a project aimed at the development of an artificial weaning diet was initiated. Initially, the chemical composition (proximate composition, amino acid, fatty acid and mineral element profile) of juvenile H. midae was analyzed, as a general lack of such information was identified in a review. Due to the lack of knowledge on the nutritional requirements of H. midae, the formulation of the weaning diet was based on the essential amino acid (EAA) pattern of the shucked tissue, and the known nutrient requirements of haliotids. Subsequently, a water stable gel and pellet form of the diet were developed. The best water stability of a gel was obtained with a 1:3 agar/gelatine mixture which retained 70.7 ± 2.7 % of its dry weight after 24 h. Starch based pellets, however, retained 89.0 ± 0.6 % of their dry weight after 24 h. In a comparative growth trial, pellets produced a significantly better increase in SL and weight than gels after only 15 days. This was probably due to the better water stability of pellets, which resulted in a better nutritional quality than in gels. The feeding behaviour on both forms of the diet did not differ. Activity patterns were exclusively nocturnal and feeding frequency was consistently low. The percentage composition of the pelleted weaning diet, on a dry weight basis, was 5 % casein, 15 % gelatine, 15 % fish meal, 10 % Spirulina spp., 2.5 % fish oil, 2.5 % sunflower oil, 21.0 % dextrin, 23.0 % starch, 4.0 % of a mineral and 2.0 % of a vitamin mixture. The correlation coefficient between the EAA pattern of H. midae and the dietary EAA pattern was r⁷= 0.8989. Pellets were fed to juveniles in a 30 day growth trial to study the effect of photoperiod (12, 16, 20 and 23 hours of darkness) on growth and general nutritional parameters. A comparative experiment feeding diatoms was conducted under a 12hL: 12hD light regime at the same time. The SL and weight of the juveniles did not increase significantly with an increase in hours of darkness. The growth of juveniles fed on pellets did not differ significantly from those fed on diatoms. Percentage feed consumption (PFC), percentage feeding rate (PFR), feed conversion ratio (FCR), protein efficiency ratio (PER) and percentage protein deposited (PPD) were determined for the animals fed on pellets. None of the parameters were significantly affected by photoperiod. However, there were trends in that PFC increased with longer periods of darkness, while PPD decreased. The FCRs (0.44 ± 0.04 to 0.60 ± 0.19) and PERs (5.06 ± 1.74 to 6.64 ± 0.77) indicated that juveniles used the feed, and in particular the protein, very efficiently. Photoperiod did not have an effect on the specific activity of the digestive enzymes amylase, protease and lipase. The specific activity of amylase in the juveniles fed on diatoms was significantly higher than in the pellet fed groups. This was surprising as the main carbohydrate of diatoms is the ß-(l-3) glucan chrysolaminarin, and not starch, a ß-(l-4) glucan. Protease specific activity, on the other hand, was significantly higher in the pellet fed groups, indicating an ability to adapt to the high protein content in the artificial diet (35.48 %), compared to diatoms which had a protein content of 5 %. The specific activity of lipase did not differ significantly between groups, probably because of a similar lipid concentration (5 - 10 %) in diatoms and pellets. Finally, the effect of stocking density, ranging from 1250 to 10,000 juveniles/m2, on the growth of juveniles was evaluated. A model of hatchery productivity was developed based on this investigation. Hatchery productivity was defined as the number of juveniles per unit space reared through to the grow-out stage per unit time. The model predicted that maximum productivity would be achieved at a stocking density of 10,000 juveniles/m2. The results have shown that H. midae can be successfully weaned on an artificial diet, as the growth on the diet was not significantly different to growth obtained on diatoms. Long-term growth trials are needed to confirm these results. The importance of standardized experiments on the nutritional requirements and digestibility of abalone was emphasized. The importance of improved artificial diets, optimal culture conditions, as well as the application of biotechnological techniques to further abalone aquaculture was highlighted.
13
Dlaza, Thembinkozi Steven. "Growth of juvenile abalone under aquaculture conditions." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&.
Full textAbstract:
The aim of this research was, first to test the suitability of different seaweeds and formulated feeds as food for post-weaning juvenile South African abalone and secondly, to test the effects of basket design on the growth of grow-out juvenile abalone in both flow-through and re-circulation systems.
14
Wood, A. D. (Aidan David). "Aspects of the biology and ecology of the South African abalone Haliotis midae Linnaeus, 1758 (Mollusca Gastropoda) along the eastern Cape and Ciskei coast." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005063.
Full textAbstract:
The South African abalone Haliotis midae Linnaeus, 1758, is an important commercial, recreational and aquaculture mollusc species. It is the largest of the six haliotid species found in South African waters and has the second largest distributional range aside from Haliotis spadicea which is widely exploited by rock and surf anglers as bait. Analysis of population structure at Great Fish Point revealed that H. midae exhibited a high degree of microhabitat specificity, and that while dietary habits played a role in habitat selection, it was ultimately the activities of predators which confined size classes to particular niches and restricted all animals to nocturnal activities. Large (> 100 mm SL) exposed animals relied on shell thickness and adhesion to combat predators, while small (> 45 mm SL) sub-boulder animals and medium sized (50 - 95 mm SL) animals relied on their cryptic microhabitats and the protective spine canopies of co-resident urchins (Parechinus angulosus) for daytime protection. Populations of H. midae were discontinuously distributed along the coast, occupying small isolated reefs which offered a suitable array of microhabitats and a good food supply. They mostly inhabited shallow intertidal and subtidal reefs, but were occasionally encountered on deeper subtidal reefs at 4 - 5 meters. Mean length- and width-at-age were determined from growth rings composed of alternate conchiolin (dark) and aragonite (white) bands in the internal nacreous shell layer. Growth was described by the Special Von Bertalanffy growth equation: Lt(mm) = 176.998918 (1 - e⁻°·²⁴²⁴¹⁹⁽t ⁺ °·⁴⁹⁵⁴⁹⁴⁾) Wt(mm) = 159.705689 (1 - e⁻°·¹⁹⁵⁴³⁹⁽t ⁺ °·²¹¹⁶⁾) The ageing technique used was validated for animals from Great Fish Point and Mgwalana using independent tag-return data. The same data provided evidence that growth rates varied between animals from Great Fish Point and Bird Island. The growth data also showed that H. midae exhibited a high degree of individual variation in growth rate. Males and females exhibited similar growth rates. Exposed large animals showed a preference for red seaweeds, in particular Plocamium corallorhiza and Hypnea spicifera, while small sub-boulder cryptic animals included larger proportions of brown (Ralfsia expansa) and green (VIva spp.) algae in their diets. Exposed individuals also exhibited a higher degree of selectivity towards prey items, but in general, stomach contents reflected the most abundant seaweed types. Both drift and attached algal species were utilized by H. midae which was a nocturnal feeder. Pigments from red algae were incorporated into the shell layers giving the shells a pink or brick red colour. Haliotis midae is a dioecious broadcast spawner. Gonad Bulk Indices in combination with detailed histological examination of gonads showed that individuals were iteroparous, asynchronous spawners and that the breeding season extended from March through to October, although the peak spawning activity was between April and June. Males and females can spawn partially, totally or not at all, with atresia of residual gametes occurring after spawning. There is no resting stage, and gametogenesis is initiated directly after spawning. The structure of the ovary and testis and the process of gametogenesis is typical of haliotid species. AI: 1 sex ratio was observed from all populations studied. Sexual maturity was first attained in the 40 - 59 mm SL size class, although evidence for the smallest size at first spawning was recorded at 54.6 mm SL for females and 69 mm SL for males. Sizes at 50% sexual maturity were 72.5 mm SL (52.8 mm SW) at Great Fish Point, 72.5 mm SL (57.4 mm SW) at Mgwalana, 73.7 mm SL (51.2 mm SW) at Cape Recife, and 73.5 mm SL (53.8 mm SW) at Kelly's Beach. Haliotis midae was typically highly fecund, although a high degree of variation resulting in poor relationships between fecundity/shell length and gonad weight/shell length. The relationship between fecundity and gonad weight was linear. In the Eastern Cape, H. midae possessed a faster growth rate, smaller size at sexual maturity, smaller maximum size and lower longevity when compared to con specifics in Western Cape waters. A smaller minimum legal size of 93 mm SW is proposed for Eastern Cape animals and it is suggested that the closed season be moved to the peak spawning period between April and June. The benefit of a closed season during the spawning period is questioned, and the feasibility of closed areas as a management option for H. midae in the Eastern Cape is discussed.
15
Sales, James. "Nutrient digestibility in South African abalone (Haliotis Midae L.)." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1005150.
Full textAbstract:
The evaluation of potential alternative protein sources for the formulation of least-cost optimal diets to satisfy the nutrient requirements of South African abalone (Haliotis midae) has been hampered by the absence of a suitable, practical, replicable and reliable digestibility technique. A suitable lowcost faeces collection technique was developed in this study to obtain suitable quantities of excreta for analysis from this species. Acid-insoluble ash was identified as a reliable, replicable and safe internal marker in comparison to chromic oxide and crude fibre for use in nutrient digestibility studies with H. midae. This was validated by the consistency and repeatability of the results and by comparison to total collection of faeces. The traditional substitution method used in digestibility studies with fish to evaluate protein digestibility of feed ingredients was found to be unsuitable for H. midae. Apparent protein digestibility values exceeding 100 % derived through this method could be attributed to associative effects between feed ingredients, differential diet and faecal nutrient leaching, and mathematical artifacts in calculations when using substitution versus single protein diets. An ingredient particle size of less than 450 μm in comparison to particle size classes of above 450 μm was shown to enhance nutrient (dry matter, organic matter, protein, fat) digestibility and minimise dry matter leaching from diets. The dietary inclusion level of both pre-gelatinised maize starch and a-cellulose did not influence (P > 0.05) apparent nutrient (protein, fat, fiber, starch) digestibility. Using the above digestibility protocol amino acid availability of all plants ingredients currently used in the South African animal industry was evaluated for H. midae. Soybean meal (96.86 %) and lupins (96.51 %) presented the highest apparent mean amino acid availability of all plant protein ingredients evaluated with H. midae. Canola meal (94.21 %), faba beans (92.87 %) sunflower meal (92.77 %), peanut meal (87.39 %) and cottonseed meal (85.15 %) presented higher apparent mean amino acid availability values than fish meal (82.75 %). Apparent protein digestibility was highly correlated (r = 0.99) with mean apparent amino acid availability, while true amino acid availability was 1.88 % units higher than apparent amino acid availability for all ingredients tested. Predicted apparent protein digestibility in compound diets was within 1.1-6.5 % of determined values. Calcium phosphate mono dibasic presented the lowest (P < 0.05) dietary phosphorus leaching (51.51 % maximum) and highest apparent phosphorus digestibility (66.27 %) in comparison to other inorganic phosphorus sources. Based on the method of direct experimentation to determine the optimal dietary protein level using graded levels of dietary protein 28.1-35.9 % dietary protein from good quality sources is recommended for maximum growth of juvenile H. midae. This study provides a scientifically sound research tool including a faecal collection technique, suitable marker and assay technique that could be use in further studies to improve least-cost diet formulation for H. midae. Future nutritional studies in H. midae should primarily concentrate on reducing dietary nutrient leaching and improving the intake of nutrients in order to properly evaluate responses of this species to different dietary regimes.
16
Shipton, Thomas A. "The protein requirements of the South African abalone, Haliotis midae." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005159.
Full textAbstract:
The potential to reduce feed formulation costs by the replacement of existing proteinsources in artificial feeds for Haliotis midae was assessed. A comparison between the efficacy of the direct method and chromic oxide marker techniques in determining apparent protein digestibility coefficients, revealed that while the former was not a suitable methodology for use with this species, the latter produced replicable and reliable results. It was established that the chromic oxide marker is inert, is not absorbed by the abalone, does not interfere with the digestive processes and moves through the intestine at the same rate to the protein. However, as this method was time consuming and expensive to implement, a multienzyme pH-stat in vitro protein digestibility technique using a three enzyme system was employed to rapidly assess the protein quality of 34 protein sources. The efficacy of the technique was established by correlating the in vitro digestibility estimates with in vivo digestibility coefficients obtained using the chromic oxide marker technique. The highest degree of in vivo predictability was attained when protein sources were separated according to origin, and significant correlations between either animal (r²=0.89, P<0.004) or plant (r²=0.79, P<0.04) protein sources were found. The effect of animal size on the qualitative protein requirements of two size classes of H.midae was assessed by feeding 12 isonitrogenous and isoenergetic single protein diets to juvenile and young adult animals (10-20 and 40-50mm shell length). The criteria for protein source selection were their bioavailability as determined using the pH-stat in vitro digestibility technique, and their cost and availability within South Africa. The protein sources identified for the trial comprised four fishmeals, casein, spirulina, abalone viscera silage, brewery waste, torula yeast, carcass, sunflower and cotton meals. The results indicated that in terms of growth and feed efficiency, the fishmeals and spirulina were the most suitable candidates as primary protein sources in formulated feeds for H.midae, and with the exceptions of the carcass meal and brewery waste, the remaining protein sources demonstrated promise as partial primary protein source replacements. The smaller size class of abalone displayed significantly reduced growth, feed and protein efficiency than their larger counterparts. In terms of feed conversion and growth response, two-way analysis of variance revealed significant interactions between protein source and animal size, suggesting that qualitative differences exist between the dietary protein requirements of the juvenile and young adult abalone. The commercial implication of thisfinding was discussed. An evaluation was undertaken to determine the effects of the partial and total replacement of dietary fishmeal with selected plant protein sources on growth and nutritional indices of juvenile H.midae. A commercial “Abfeed” formulation in which 100% of the protein component comprised LT-fishmeal was employed as a control. Fifteen isonitrogenous experimental diets were formulated in which the LT fishmeal was substituted at either 10, 15, 30, 50, 75 or 100% with either spirulina, semolina, ground maize, torula yeast, soya, sunflower or corn gluten meals or combinations thereof. No significant differences were found in the growth rates between the control diet and those diets in which 30% of the fishmeal component had been replaced by either soya, sunflower meal, or torula yeast. In addition, 50% of the fishmeal component could be substituted with either soya meal or spirulina without affecting growth. Replacement of either 75 or 100% of the fishmeal had a significant negative affect on growth. Pearson product moment correlations between dietary lysine levels and either growth rates or protein efficiency ratios revealed positive correlations (r=0.77, P=0.0005; r=0.52, P=0.04 respectively) suggesting that lysine may have been the first limiting amino acid in these diets. Carcass analysis revealed that dietary protein source had no significant effect on body composition. An assessment of the dietary arginine requirement of juvenile H.midae using whole proteins to supply graded levels of dietary arginine did not promote a growth response. It was concluded that arginine is probably not the first limiting amino acid in formulated feeds for H.midae. An assessment of the dietary lysine requirement of juvenile H.midae using two micro-encapsulation techniques (gelatin/acacia colloid or cellulose acetate phthalate) was not successful. The efficacy of the encapsulation techniques were established and an assessment of the degree of lysine supplementation undertaken. Failure of the crystalline lysine enriched diets to promote growth suggests that the prospects for using crystalline amino acids in essential amino acid requirement studies in H.midae is low. The results of the present study indicate that the prospects for replacing fishmeal with cheaper alternative protein sources in artificial feeds for H.midae is promising. Furthermore, while the technical difficulties such as the determination of the essential amino acid requirements of the abalone precluded the application of “least cost” programming, the prospects for its future application are promising.
17
Naylor, Matthew Aubrey. "Water quality dynamics in an experimental serial-use raceway and its effects on growth of South African abalone, Haliotis midae." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005181.
Full textAbstract:
An understanding of species specific water quality requirements is essential for efficient production of aquaculture products, an aspect not well documented for the land-based culture of the South African abalone, Haliotis midae. In order for the industry to remain competitive in international markets, efficient use of water supplies and the development of water reuse technology is needed. This study assessed the changes in water quality between tanks in a tiered serial-use raceway in relation to accumulated biomass and water flow and estimated the flow index (FI) (L h⁻¹ kg⁻¹) at which growth becomes significantly affected. The effect of dietary protein level, supplementation of pure oxygen and addition of sodium hydroxide (NaOH⁻) on water quality and fundamental production parameters in the serial-use raceways was also assessed. The serial-use raceways were used as a tool to create a range of water quality conditions at which the growth, feed conversion ratio (FCR) and condition factor (CF) of "cocktail" size (60 – 70 mm) H. midae could be monitored. The metabolic activity of the abalone resulted in a deterioration in water quality between tanks in series. pH (r² = 0.99; p < 0.001) and dissolved oxygen concentration (r² = 0.99; p < 0.001) were positively correlated with flow index (pH = 7.38 FI°·°² ; dissolved oxygen = 6.92 FI°·°⁴), while free ammonia nitrogen (FAN) (r² = 0.99, p < 0.001) and nitrite (NO²⁻ - N) (r² = 0.93, p < 0.001) were negatively correlated with flow index (FAN = 8.02 FI⁻°·⁷¹). Nitrite concentrations increased over time indicating colonisation of Nitrosomonas bacteria on the basket surfaces. A flow index of 7.2 – 9.0 L h⁻¹ kg⁻¹ was estimated as the minimum to avoid significant reductions in weight and shell length gain and increases in FCR values. Total ammonia nitrogen (TAN) and FAN concentrations were significantly correlated to dietary protein (P) (t = 6.63, p < 0.0001 and t = 6.41, p < 0.0001, respectively) and flow index (t = 5.42, p < 0.0001 and t = 3.9, p < 0.0002, respectively) and could be estimated using the models TAN = 9.73 P – 110.3 log (FI), and FAN = 0.132 P – 1.10 log (FI). Mean FAN concentrations were 67 and 41 % lower in tanks fed a diet containing 22 and 26 % protein respectively, when compared to tanks fed a 33 % protein diet. Supplementation with pure oxygen (103 ± 8 % saturation) improved shell length gain (t = 3.45, p = 0.026) in abalone exposed to high FAN (2.43 ± 1.1 μg L⁻¹) and low pH (7.6 ± 0.13), relative to a treatment with no oxygen supplementation (92 ± 6 % saturation). Addition of a sodium hydroxide solution resulted in elevated mean pH in treatment raceways when compared to control raceways. The increased pH resulted in significantly higher weight gain (g abalone⁻¹) (F₁·₁₂ = 4.51; p = 0.055) and shell length gain (mm abalone⁻¹) (F₁·₁₂ = 4.56; p = 0.054) at an α-error level of < 5.5 %. In two trials, weight gain and shell length gain were significantly correlated to pH (p < 0.001), and multiple regression of pH, dissolved oxygen and FAN consistently revealed pH to be the best predictor of growth. It is therefore suggested that decreasing pH is the first limiting water quality variable for abalone in serial-use raceways. As a decrease in water pH is linked to respiration by the abalone and subsequent increase in dissolved carbon dioxide (CO₂) concentration, future studies should examine the effects of CO₂ on H. midae metabolic rate, calcification rate and health. The results of this study will contribute toward our understanding of the specific water quality requirements for H. midae in commercial aquaculture systems, and influence the design and management procedures for abalone water reuse systems.
18
Makhande, Emmanuel Denis. "Growth of the South African abalone (Haliotis Midae) on three diets, under commercial conditions." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/755.
Full textAbstract:
Haliotis midae is the cornerstone of the South African abalone fishery. For more than a decade, the wild abalone stock of South Africa has suffered decline due to over-exploitation and illegal activities such as poaching. Prior to 1970, no regulations were in place concerning the annual landings. As a result the fishery was exploited as if it were an infinite resource. It is this initial uncontrolled harvesting (regardless of age) and poaching that has driven the abalone resource decline. Due to the slow growth rate exhibited by abalone as a species, natural replenishment of wild stock following exploitation and poaching was far below the rate of exploitation of this resource. Studies on the growth of abalone have mainly been conducted under laboratory conditions. The purpose of this study was to measure the growth of abalone, fed different diets, under commercial culture conditions. Three food types were used namely; commercial pellets, seaweed (Ulva spp.) and dried kelp bars (Ecklonia maxima). Four diets were obtained from the three food types namely; combination of commercial pellets and seaweed (Diet A), commercial pellets only (Diet B), seaweed only (Diet C) and dried kelp bars only (Diet D). The food types used in this study represent both artificial (Commercial pellets) and natural feeds (seaweed and kelp) used in commercial abalone culture. The growth of two cohorts (40-50 mm and 50-60 mm) was followed over a 426 day period, with data for the first 183 days being used for statistical analysis to determine performance of a given diet. The best growth rates were found in abalone fed Diet A (40-50 mm: 2.64 mm.month-1; 50-60 mm 2.78: mm.month-1) and B (40-50 mm: 2.20 mm.month-1; 50-60 mm: 2.35: mm.month-1). These (Diets A and B) gave higher growth rates when compared to Diets C and D (natural diets), whose growth rates ranged between 0.50 mm.month-1 and 1.71 mm.month-1 for both cohorts. Also observed in this study was that, the mixture of formulated diet and seaweed gave better growth than formulated diet given exclusively.
19
Yearsley, Rowan David. "Water quality, abalone growth and the potential for integrated mariculture on a South African abalone Haliotis midae L. farm." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005180.
Full textAbstract:
Abalone Haliotis midae farming in South Africa is highly intensive, employing pump-ashore, flow-through systems. Despite the known sensitivity of abalone to water quality, there is only a rudimentary understanding of water quality dynamics on South African abalone farms and its effects on abalone production. Furthermore, the potential for reusing the relatively dilute abalone farm effluent to culture other animal species has not been investigated. This study investigated the dynamics of water quality and growth on a South African abalone farm and assessed the suitability of the effluent for the culture of silver kob Argyrosomus inodorus and bloodworm Arenicola loveni loveni. Monitoring of water quality and abalone growth in abalone tanks revealed that oxygen concentrations decreased, while H⁺ ion and free-ammonia (NH₃) concentration increased in a gradient between the inflow and outflow. Abalone growth was positively correlated with oxygen concentration and negatively correlated with free-ammonia and H⁺ ion concentration. The oxygen (O) concentration of the farm influent was dependent upon the influents’ temperature (T) and was described by the relationship O (mg L⁻¹) = 11.244 – 0.208T (r²=0.74). Linear regression analysis of data collected from abalone farm tanks revealed that the concentration of total ammonia at the outflow of abalone tanks (μg TAN L⁻¹) was dependant upon temperature (°C), flow-rate (L s⁻¹ kg⁻¹ H. midae), abalone size (g) and length of time since the tank was last cleaned (d) (n = 125, r² = 0.80). The production of total ammonia (μg TAN s⁻¹ kg⁻¹) was related to temperature, abalone size and days that the tanks remained un-cleaned (n = 125; r² = 0.81). A diurnal cycle of respiration was evident in abalone tanks with higher oxygen consumption and H+ ion production at night. The oxygen concentration of farm effluent was related to temperature, farm biomass and flow rate by means of a linear regression equation (n = 40; r² = 0.69). The results demonstrated the importance of optimising the flow-rate per unit of biomass for various temperatures and sizes of abalone. As abalone size and temperature cannot be controlled under farm conditions, the flow-rate per unit of biomass which the abalone culture system receives will determine the quality of the culture water. The specific growth rate (0.48 ± 0.01 % BW d⁻¹), mortality (1.8 ± 0.5 %), feed conversion ratio (3.0 ± 0.2) and protein efficiency ratio (1.0 ± 0.1) of silver kob kept in either abalone farm effluent or control seawater for 120 days did not differ significantly (t-test, P>0.05). A 90 day growth trial indicated that abalone farm effluent is a suitable culture medium for bloodworm. Bloodworm supplied with control seawater lost weight at 0.19 ± 0.04 % BW d-1, while those given abalone effluent grew at 0.39 ± 0.07 % BW d⁻¹. Mortality was 6 ± 3 % in effluent and 11 ± 8 % in seawater. The bloodworm were efficient at processing solid waste. Abalone farm effluent initially contained 7.7 ± 13 mg L⁻¹ more suspended solids than control seawater, which contained 3.5 ± 0.5 mg L⁻¹, but after passing through bloodworm systems the concentration in abalone effluent was reduced to only 1.4 ± 3.5 mg L⁻¹ above that in control seawater. Therefore, abalone farm effluent could be reused as a culture medium for both silver kob and bloodworm. Future work is needed to investigate aspects of the feasibility of such systems such as growth rates at different sizes and stocking densities.
20
Ockert, Candice. "Identification of molecular markers for the diagnostic identification of the intracellular prokaryote associated with the appearance of withering syndrome in the abalone Haliotis midae." Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1148.
Full text
21
Francis, Tamson L. "The effects of differences in feeding regime and of export simulations on the growth of the abalone Haliotis midae Linnaeus." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3633_1258099775.
Full textAbstract:
Beach-cast kelp (the most widely used feed for commercially grown South African abalone) is plentiful during winter months when periodic storms cause kelp to wash ashore. During summer, however, this resource is not always readily available and farmed abalone are often starved for short periods. The aim of this research was to assess how periodic kelp starvation influences growth of the commercially grown abalone, Haliotis midae Linnaeus.
22
Rhode, Clint. "Signatures of selection in natural and cultured Abalone (Haliotis midae) : a population genomics study." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79895.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The South African abalone, Haliotis midae, commonly known as perlemoen, is an economically important gastropod mollusc. Historically, this species maintained a lucrative fisheries sector; however with increasingly lower landings there has now been a shift to aquaculture. Efforts to conserve natural populations and to improve abalone aquaculture production are thus running in parallel. Previous studies reported significant disparities in parental contributions in aquaculture populations that could explain the rapid divergence of commercial stocks from wild populations. Furthermore, subtle, but significant, population differentiation has also been reported for wild populations on the west-, south-, and east coast of the South African coastline. This study therefore aimed to investigate the evolutionary forces, in particularly selection, facilitating population divergence in wild and cultured H. midae populations using a population genomics approach. By using both microsatellite- and single nucleotide polymorphism (SNP) markers it was found that approximately 10% to 27% of the H. midae genome may be influenced by selection. When incorporating these loci into analyses of population differentiation (e.g. AMOVA, factorial correspondence analysis and estimates of genetic distance) there was a marked increase in genetic divergence between wild and cultured populations (especially when using microsatellite loci) and amongst populations from different geographic regions (particularly supported by the SNP loci). The differences in population clustering as highlighted by microsatellite- and SNP markers can most likely be attributed to the genomic distribution of the respective loci: The SNP markers were developed from EST sequences and therefore mostly represents protein structural variation; whereas the microsatellite markers, found to be putatively under selection, were mainly located in regulatory motifs. The results of this study therefore confirmed previous observations of divergence amongst wild- and cultured populations, but more importantly demonstrated that selection is an important factor driving this divergence. In wild populations selection probably facilitates adaptation to local environmental conditions, whilst amongst aquaculture population adaptation to captivity, husbandry practices and artificial selection may be important determinants. There is evidence for population bottlenecks in wild- and cultured populations; nonetheless long-term effective population sizes seem to be large. Amongst the wild populations, however, short-term population sizes appear to be small most likely due to differential spawning rates amongst reproductively active animals leading to temporal fluctuation in genetic diversity. The results indicate that contact between wild and cultured abalone should be minimised to prevent any adverse effects due to outbreeding depression. With regards to conservation, an emphasis on maintaining adaptive diversity of the wild stocks might be warranted. Continued genetic monitoring is advisable for both wild and cultured abalone populations as to optimally manage the abalone resource for both conservation and commercial viability and sustainability.
AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse perlemoen, Haliotis midae, is 'n ekonomies belangrike buikpotige weekdier. Histories het hierdie spesie 'n winsgewende vissery gehandhaaf, maar met steeds dalende vangste is daar nou 'n verskuiwing na akwakultuur. Pogings om natuurlike populasies te bewaar en perlemoen te verbeter vir verhoogde akwakultuur produksie loop dus in parallel. Vorige studies het bevind dat beduidende verskille in ouerlike bydraes tot die nageslag, in akwakultuur populasies, kan verduidelik hoekom die populasies so vinnig divergeer van die wilde voorouers. Verder, is subtiele, maar betekenisvolle genetiese differensiasie tussen wilde populasies aan die wes-, suid-en ooskus van die land gevind. Hierdie studie is dus daarop gemik om ondersoek in te stel na die mate waartoe verskeie evolusionêre prosesse, in besonder seleksie, die populasie divergensie in beide wilde en gekweekte H. midae teweegbring deur gebruik te maak van ‘n populasie genomika benadering. Deur gebruik te maak van beide mikrosatelliet- en enkel nukleotied polimorfisme (ENP) merkers is dit bevind dat ongeveer 10% tot 27% van die H. midae genoom moontlik beïnvloed word deur seleksie. Met die gebruik van loki onder seleksie tydens die ontleding van populasie differensiasie (bv. AMOVA, faktoriaal korrespondensie analise en genetiese afstand ramings) was daar 'n merkbare toename in genetiese divergensie tussen wilde- en gekweekte populasies (veral wanneer mikrosatelliet loki gebruik is) en onder die populasies vanuit verskillende geografiese gebiede (veral ondersteun deur die ENP loki). Die verskille in die populasie groeperings soos uitgelig deur die mikrosatelliet- en ENP-merkers kan waarskynlik toegeskryf word aan die genomiese verspreiding van die onderskeie loki: Die ENP-merkers is ontwikkel vanaf uitgedrukte volgorde merker (UVM) volgordes en daarom verteenwoordig dit meestal proteïen strukturele veranderinge, terwyl mikrosatelliet merkers eerder in regulatoriese motiewe geleë is. Die resultate van hierdie studie steun dus vorige waarnemings, maar meer belangrik, het dit getoon dat seleksie ‘n betekenisvolle faktor in populasie divergensie in beide wilde en gekweekte populasies is. In wilde populasies fasiliteer seleksie waarskynlik die aanpassing tot plaaslike omgewingstoestande terwyl seleksie onder die gekweekte populasies teweeggebring kan word as gevolg van aanpassing tot aanhouding, boerdery praktyke en kunsmatige seleksie. Daar is bewyse vir populasie bottelnekke in wilde- en gekweekte populasies; tog blyk langtermyn effektiewe populasiegroottes om redelik groot te wees. Onder die wilde populasies is egter gevind dat kort-termyn populasiegroottes klein kan wees, waarskynlik as gevolg van differensiële broeikoerse onder reproduktiewe diere. Dit het tot gevolg dat daar beduidende fluktuasies is in temporale genetiese diversiteit. Die resultate dui daarop dat kontak tussen wilde en gekweekte perlemoen tot 'n minimum beperk moet word om enige nadelige effekte weens uitteling depressie te voorkom. Verder, met betrekking tot bewaring, is ‘n klem op die handhawing van aangepaste genetiese diversitiet dalk geregverdig. Voortgesette genetiese monitering word aanbeveel vir beide wilde- en gekweekte perlemoen populasies ter wille van die optimale bestuur van die perlemoen hulpbron vir beide bewaring en kommersiële lewensvatbaarheid en volhoubaarheid.
International Foundation for Science
National Research Foundation of South Africa
Stellenbosch University
23
Dixon, Mark Geoffrey. "The effect of temperature and photoperiod on the digestive physiology of the South African abalone Haliotis midae." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005120.
Full textAbstract:
Inadequate information of the nutritive physiology and the dietary requirements of abalone are the principle factors that currently limit the development of a formulated feed for the commercial culture of Haliotis midae. The need to develop a method to determine apparent digestibility co-efficient's for abalone in order to facilitate further applied nutritional research was identified. Animals between 50 and 80 mm were collected from natural stocks along the east Cape coast of South Africa at Port Alfred and Great Fish point, and acclimated to laboratory conditions. Initial trials demonstrated that H. midae accepted and preferred a semi-purified diet to the seaweed Plocamium corallorhiza, one of the main components of it's natural diet. A technique of determining apparent digestibility co-efficient's (ADC) using the indirect method with chromic oxide as an inert marker was developed. Digestibility trials yielded higher dry matter (DMADC) and crude protein apparent digestibility co-efficient's (CPADC) for the semi-purified diet than for two species of algae, Gelidium amanzii and P. corallorhiza (83.7% and 95.6%, 70.7% and 80.0%, and 29.9% and 57.3% respectively). The ability of the animals to utilize terrestrial animal and plant ingredients efficiently makes it feasible to use conventional feed ingredients in formulated feeds for H. midae. Trials to determine the effect of different temperatures (15°C, 18°C and 22°C) on DMADC and CPADC of the semipurified diet showed that peak digestibility occurred at 18°C. There was also a positive relationship between temperature and consumption rate. Although no enzyme studies with H. midae have been conducted, the peak ADC's at 18°C is attributed to an increase in enzyme activity at this temperature. Transit time, an inverse function of temperature and consumption, is considered to be responsible for the decrease in the ADC' s at 22°C in conjunction with a possible decrease in enzyme activity at this temperature. A photoperiod trial to investigate the effect of darkness on DMADC and CPADC of the semi-purified diet revealed that digestive efficiency decreased with increasing hours of darkness. There was also a positive relationship between duration of darkness and the rate of consumption. The decrease in ADC's is attributed to decreased transit times as the duration of darkness increased . The contribution of this project to the understanding of abalone nutrition, the development of a formulated abalone feed and systems design for abalone farms is discussed.
24
Elias, John Peter. "Ecophysiology of the Blacklip abalone Haliotis rubra leach : metabolic aspects of muscle function and blood oxygen delivery in a commercially important species." Monash University, School of Biological Sciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/5664.
Full text
25
Naidoo, Krishnaveni. "Testing the suitability of local seaweeds and formulated feed as a food source for abalone (Haliotis midae Linnaeus) in an Integrated Land-based Aquaculture System." Thesis, Online Access, 2008. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_9129_1263510405.pdf.
Full text
26
Riddin, Nicholas Alwyn. "Growth and gonad size in cultured South African abalone, Haliotis midae." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001651.
Full textAbstract:
According to farm records, cultured Haliotis midae (50-70 g.abalone⁻¹) were growing 10% slower in winter when compared to summer. This reduction in growth rate also coincided with enlarged gonads. Initial trials showed that there were differences in mean monthly growth rates ranging from 1.97 – 5.14 g abalone⁻¹ month⁻¹, and gonad bulk index (GBI) also varied between months (GBI range: 26.88 ± 12.87 to 51.03 ± 34.47). The investment of energy into gonad tissue growth did not compromise whole body growth as the abalone continued to gain weight throughout the reproductive periods, probably due to gonadal growth. Growth of this size class of abalone was not influenced by water temperature or day length, suggesting favourable on-farm culture conditions (regression analyses, p > 0.05). There is no need to implement a seasonal dietary regime. Cultured H. midae were fed artificial diets with different protein sources, including only soya, only fishmeal, a combination of soya and fishmeal, and these were compared to kelp-fed abalone. Kelp-fed abalone grew slower than those fed artificial feeds (p>0.05). Gonad growth was the greatest when soya meal was included in the diet (average GBI: 74.91 ± 23.31), while the average gonad size of abalone fed the fishmealbased diet had gonads which were 38% smaller, and kelp-fed abalone had gonads which were 75% smaller than those of the abalone fed on diets containing soya meal. The increased gonad mass in abalone fed on diets including soya meal could be attributed to phytoestrogenic activity, as a result of the presence of isoflavones found in the soya plant; this remains to be tested. The use of soya in brood stock diet development is advised. The influence of dietary protein to energy ratio (1.41 – 2.46 g MJ⁻¹) on growth and gonad size was tested. Protein and energy levels within the ranges tested (22 and 33% protein; 13.5 and 15.6 MJ kg⁻¹) did not interact to influence growth rates of cultured H. midae. GBI increased from 50.67 ± 4.16 to 83.93 ± 9.35 units as a function of dietary protein to energy ratio (y = 42.02 x⁰·⁸¹; r² = 0.19; regression analysis: F₁¸₃₈ = 8.9; p = 0.005). In addition, protein level influenced gonad size, with gonad growth being greater in abalone fed the high protein diet (factorial ANOVA: F₁¸₃₂ = 7.1, p = 0.012). Canning yields were reduced by 7% when the protein content was increased, while increasing the quantity of dietary energy improved canning yields by ~ 6% (one-way ANOVA: F₁¸₂₈ = 14.4, p= 0.001). The present study provided evidence that although growth rates are varying seasonally, reproductive investment is not hindering weight gain. Gonad growth can be influenced if desired by farms, depending on the level of soya inclusion, as well as the protein to energy ratio in the diet. Monthly variation in growth and gonad size, as well as the influence of diet on gonad growth were highlighted, and the implications for farm application and further research were discussed.
27
Ayres, Devin William Philip. "Effect of diet and sex-sorting on growth and gonad development in farmed South African abalone, Haliotis midae." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1010856.
Full textAbstract:
Abalone, Haliotis midae, farmers in South Africa that feed formulated diets reported a periodic drop in abalone growth during periods of increased gonad development. A large drop in abalone biomass was noticed after presumed spawning events. This study was aimed to determine the effect of diet and sex-sorting on gonad development in abalone. Experiments were conducted on a commercial abalone farm from July 2012 to the end of June 2013. Isonitrogenous and isoenergetic diets were formulated with two protein sources. A fishmeal and soybean meal (S-diet) diet and a fishmeal only (F-diet) diet were fed to abalone (50 - 70 g abalone⁻¹) over 12 months. Weight and length gain, gonad bulk index (GBI), visceral index (%) and meat mass index (%) were determined monthly and seasonally. A histological study on the female gonads was conducted. This study also included an experiment to test the effect of sex-sorting (70 - 80 g abalone⁻¹) on growth and body composition with treatments including males (M), females (F) and equal numbers of males and females (MF). Weight gain and length gain were faster in S-diet-fed abalone (RM-ANOVA, F ₍₁, ₁₆₎ = 7.77, p = 0.01; F ₍₁, ₆₉₎ = 49.9, p < 0.001, respectively). Gonad development was significantly affected by the inclusion of soybean meal with S-diet-fed abalone showing higher GBI-values than F-diet-fed abalone (RM-ANOVA, F ₍₁, ₃₃)= 16.22, p = 0.0003). Male abalone had higher GBI-values than females (RM-ANOVA, F ₍₁, ₃₃₎ = 39.87, p < 0.0001). There was no significant difference in average feed conversion ratio (FCR) between diets over time (RM-ANOVA, F ₍₁, ₂₁₎ = 0.008, p = 0.97). However, average FCR-values were significantly highest between November 2012 and March 2013, the presumed spawning season. The visceral mass (gut and gonad) as a proportion of whole mass (visceral index, %) was significantly higher in abalone fed the S-diet (RM-ANOVA; F ₍₁, ₆₉₎ = 68.06, p < 0.0001). There was no difference in meat mass index (%) between diets for both male and female abalone (RM-ANOVA; F ₍₇, ₂₄₈₎ = 0.80, p = 0.60; F ₍₇, ₂₄₁₎ = 1.7, p = 0.11,respectively). Meat mass index significantly decreased from September 2012 to February 2013 coinciding with the period of high GBI-values. The distribution of oocyte maturity stages differed between diets. The majority of oocytes within S-diet-fed abalone were fully mature stage 8 oocytes compared to a majority of stage 7 oocytes in F-diet-fed abalone. Histology corroborated peaks in GBI-values for abalone fed both diets. There was no significant difference in growth, GBI, visceral index (%) and meat mass index (%) between abalone sorted into monosex and mixed-sex populations. Thus, the presence of the opposite sex did not have an effect on growth and gonad mass in H. midae. The phytoestrogens daidzin, glycitin, genistin, daidzein, glycitein and genistein were present in soybean meal and only traceable amounts were found in the F-diet. This study provided evidence that soybean meal present in formulated feed affected growth and gonad development in H.midae. The difference in the distribution of the maturity stages of oocytes was affected by diet. Sex-sorting abalone into monosex and mixed-sex populations had no influence on weight and length gain and gonad development.
28
Ruivo, Nicola Ribeiro. "Microsatellite genotyping of contributing broodstock and selected offspring of Haliotis midae submitted to a growth performance recording scheme." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21755.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: The indigenous abalone Haliotis midae is one of the most remarkable and highly exploited species of marine molluscs in South Africa. It is the only species of southern African Haliotidae to be commercially reared and has been successfully cultured for almost two decades. Its short history of domestication along with market demands and the need to develop efficiency in the production process has resulted in an increased interest in the possible genetic improvement of this species. The unhurried growth rate associated with H. midae is a cause of particular concern to the industry, predominantly with regards to profitability and competitiveness in the market place. A modest amount of work has so far been directed at establishing a means of enhancement for selective breeding on the commercial level. Genetics plays a key role in the establishment of successful improvement programmes in various aquaculture species. The aim of this study was to develop species-specific microsatellite markers for the abalone and subsequently perform parentage assignment on farm produced animals entered into a growth performance recording scheme. Animals were obtained from the hatcheries of three commercial abalone farms situated in the Walker Bay region in the Western Cape. Microsatellites were isolated using the enrichment-based FIASCO method, and characterised into perfect, imperfect and compound repeats according to the structural nature of their repetitive units. From the partial gDNA libraries obtained and 365 screened colonies, a total of 54 loci were located. PCR primers were designed for 36 markers and the 15 primer pairs that displayed loci with the highest level of polymorphism were subsequently chosen for fluorescent labelling. The markers were tested on a subset of 32 wild H. midae individuals to determine their usefulness and efficiency in genotyping. Five markers, along with five others that were previously designed, were chosen for assigning parentage to the animals submitted to the performance recording scheme. Three thousand offspring from each of the three participating farms were equally divided and reared at five different locations. From each location 20 fast growing and 20 slow growing juveniles, as well as the broodstocks, were sampled and genotyped using the ten chosen microsatellite loci. Two farms had 60% of offspring unambiguously assigned to a single parental couple. Assignments showed patterns of dominant male and female brooders, but no trend in brooders specifically contributing to fast or slow growing offspring. Parentage assignment for the third farm was, however, unsuccessful due to lack of broodstock data. In future, screening of all available broodstock will ensure acquisition of relevant pedigree information. The results obtained in this study are an initial step in the development of a genetic improvement programme for commercial Haliotis midae.
AFRIKAANSE OPSOMMING: Die inheemse skulpvis Haliotis midae is een van die mees merkwaardige en hoogs oorbenutte mariene slakspesies in Suid-Afrika. Dit is die enigste suidelike Afrika Haliotidae spesie wat kommersieel benut word en dit word al meer as twee dekades suksesvol geteel. Die spesie se kort domestiseringsgeskiedenis, toenemende mark aanvraag en die behoefte om meer effektiewe produksie daar te stel, het gelei tot toenemende belangstelling in die moontlike genetiese verbetering van die spesie. Die stadige groeitempo geassosieer met H. midae is veral ‘n punt van kommer vir die industrie, veral in terme van winsgewendheid en kompetering in die markplek. Minimale werk is sover gedoen in die daarstelling van verbetering deur selektiewe teling op ‘n kommersiële skaal. Genetika speel ’n sleutelrol in die daarstelling van suksesvolle verbeteringsprogramme van verskeie akwakultuur spesies. Die doel van hierdie studie was om spesie-spesifieke mikrosatelliet merkers vir perlemoen te ontwikkel en vervolgens ouerskapsbepaling van kommersiële diere, wat deelneem aan ‘n groeiprestasie aantekenstelsel, uit te voer. Diere is voorsien deur die teelstasies van drie kommersiële perlemoenplase geleë in die Walker Bay omgewing in die Wes-Kaap. Mikrosatelliete is geïsoleer deur die verrykings-gebaseerde FIASCO metode, en gekarakteriseer as perfekte, onderbroke of saamgestelde herhalings gebaseer op die strukturele aard van die herhalings eenhede. Vanaf die gedeeltelik gDNA biblioteke wat bekom is en 365 gesifte kolonies, is ‘n totaal van 54 loki opgespoor. PKR inleiers is ontwerp vir 36 merkers en die 15 inleierpare, wat loki met die hoogste polimorfisme geamplifiseer het, is vervolgens geselekteer vir fluoreserende merking. Die merkers is getoets op ’n kleiner groep van 32 natuurlike H. midae individue om hulle bruikbaarheid en genotiperingseffektiwiteit te bepaal. Vyf merkers is saam met vyf reeds ontwikkelde merkers gekies vir ouerskapsbepaling van die diere in die prestasie aantekenstelsel. Drieduisend nageslag diere vanaf elkeen van die drie deelnemde plase is gelykop verdeel en grootgemaak op die vyf verskillende lokaliteite. ‘n Monster van 20 vinnig groeiende en 20 stadig groeiende jong perlemoen, sowel as broeidiere, is vanaf elke lokaliteit geneem en gegenotipeer deur middel van die 10 geselekteerde mikrosatelliet loki. Sestig persent van twee van die plase se nageslag is onteenseglik toegesê aan ‘n enkele ouerpaar. Ouerskapstoekenning het patrone van dominante vroulike en manlike broeidiere getoon, maar geen tendens in terme van bydrae tot vinnig en stadig groeiende nageslag kon gevind word nie. Ouerskapstoekenning vir die derde plaas was onsuksesvol as gevolg van ’n gebrek aan data vir die broeidiere. In die toekoms sal genotipering van alle beskikbare broeidiere die daarstelling van relevante stamboominligting verseker. Die resultate verkry in hierdie studie verteenwoordig ‘n eerste stap in die ontwikkeling van ’n genetiese verbeteringsprogram vir kommersiële Haliotis midae.
29
Gerber, Maria Elizabeth (Mariette). "Quantitative assessment of yield traits between family groups of the cultured abalone, Haliotis midae, during the process of canning." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80085.
Full textAbstract:
Thesis (MScAgric)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The species Haliotis midae is of great commercial value to the South African abalone industry and is mainly exported to Asian markets, specifically China. Up to 50% is sold as canned products with H. midae registering an average canning yield of approximately 35%. The species is presently genetically undomesticated and breeding programmes are being introduced to improve a range of production traits of which growth and yield is of primary importance. The objective of the study was to determine genetic parameters such as heritability, genotypic and phenotypic correlations of yield-related traits to assess the potential genetic improvement through selective breeding. A series of yield-related parameters were identified that is of relevance to the standard abalone canning procedure. Low to moderate heritabilities where recorded for most traits, including pre-shuck/live weight (0.20 ± 0.06), post-shuck weight (0.15 ± 0.05), post-gut weight (0.15 ± 0.05), post-brine weight (0.19 ± 0.06), pre-canning weight (0.19 ± 0.06), post-canning weight (0.21 ± 0.06), shell weight (0.16 ± 0.05), canning yield percentage (0.08 ± 0.03) and shell weight to post-gut weight ratio (SW: PGW) (0.09 ± 0.04). Weight related parameters are phenotypically highly correlated (0.86 ≤ r ≤ 0.99) but show negative correlation with canning yield percentage (-0.38 ≤ r ≤ 0.04). The nett yield of abalone shows a relatively strong positive correlation with the live weight (r = 0.66). Shell length is highly heritable (h2 ≈ 0.48) and show a strong positive correlation with live weight (r = 0.94). Shell weight is also highly correlated with live weight (r = 0.80) and the SW: PGW ratio does not show a significant correlate with live weight (r = 0.03). Weight-related traits show heritability values ranging from 0.15 to 0.20 that could allow a positive genetic response. Shell length (as a linear growth parameter) shows a high heritability (h2 ≈ 0.48) and a strong positive correlation with live weight (r = 0.94) which also makes it suitable for use as a selection criterion in breeding programmes for improved growth rate. Direct selection for canning yield is compromised by the destructive nature of measurement and the low heritability (h2 < 0.10). The negative correlations between yield as a percentage and growth traits (-0.38 ≤ r ≤ 0.04) further complicate its use as a direct breeding objective. Although the canning yield as a percentage shows a decrease with an increase in live weight, the nett canning yield increases (r = 0.66) with the live weight. It is therefore recommended to use shell length as a criterion for selection for increased growth rate and nett yield, thereby optimising profitability.
AFRIKAANSE OPSOMMING: Die spesie Haliotis midae is van groot kommersiёle waarde tot die Suid-Afrikaanse perlemoenindustrie en word meestal uitgevoer na markte in Asiё, spesifiek China. Tot 50% van die perlemoen wat in Suid-Afrika geproduseer en uitgevoer word, word verblik en huidiglik is die verblikkingsopbrengspersentasie ongeveer 35%. Haliotis midae is tans geneties onderontwikkeld en die gebruik van teelprogramme word nou geimplementeer met die doel om 'n verskeidenheid eienskappe te verbeter, waarvan groei en opbrengs van primêre belang is. Die doelwit van die studie was om genetiese parameters soos oorerflikheid en ook die genotipiese en fenotipiese korrelasies van obrengsverwante eienskappe te bepaal om sodoende die potensiёle genetiese verbetering as gevolg van selektiewe teeling te assesseer. 'n Reeks obrengsverwante eienskappe is geidentifiseer wat relevant is binne bestaande en standaard kommersiёle perlemoenverblikkingsprotokolle. Lae tot matige oorerflikheidswaardes is waargeneem en sluit in lewende, of voor-ontskulpingsgewig (0.20 ± 0.06), na-ontskulpingsgewig (0.15 ± 0.05), na-oopvlekkingsgewig (0.15 ± 0.05), na-pekelgewig (0.19 ± 0.06), voor-verblikkingsgewig (0.19 ± 0.06), na-verblikkingsgewig (0.21 ± 0.06), skulpgewig (0.16 ± 0.05), verblikkingsopbrengspersentasie (0.08 ± 0.03) en 'n skulpgewig tot na-oopvlekkingsgewig verhouding (SW: PGW) (0.09 ± 0.04). Gewigsverwante parameters is fenotipies hoogs gekorreleerd met mekaar (0.86 ≤ r ≤ 0.99) maar toon 'n negatiewe korrelasie met die verblikkingsopbrengspersentasie (-0.38 ≤ r ≤ 0.04). Die netto opbrengs van perlemoen dui op 'n relatiewe sterk positiewe korrelasie met lewende gewig (r = 0.66). Skulplengte is hoogs oorerflik (h2 ≈ 0.48) en toon 'n sterk positiewe korrelasie met lewende gewig (r = 0.94). Skulpgewig is ook hoogs gekorreleerd met lewende gewig (r = 0.80) en die SW: PGW verhouding toon geen beduidende korrelasie met lewende gewig nie (r = 0.03). Gewigsverwante eienskappe toon oorerflikheidswaardes wat varieer tussen 0.15 en 0.20 en kan 'n moontlike genetiese respons lewer. Skulplengte (as 'n liniêre groeiparameter) toon 'n hoё oorerflikheid (h2 ≈ 0.48) en 'n sterk positiewe korrelasie met lewende gewig (r = 0.94) wat dit gepas maak vir gebruik as 'n seleksiekriterium in 'n teelprogram met verbeterde groeitempo as doel. Direkte seleksie in terme van verblikkingsopbrengs word ingeboet danksy die destruktiewe natuur van die metingsmetodiek asook 'n lae oorerflikheid (h2 < 0.10). Die negatiewe korrelasies tussen verblikkingsopbrengs (uitgedruk as 'n persentasie) en groeieienskappe (-0.38 ≤ r ≤ 0.04) dien as 'n verdere komplikasie in die gebruik van dié eienskap as direkte teeldoelwit. Alhoewel die verblikkingopbrengs 'n afname toon soos lewende gewig toeneem, is daar steeds 'n positiewe korrelasie tussen die netto verblikkingsopbrengs en die lewende gewig (r = 0.66). Dit word dus aangeraai om skulplengte as seleksiekriterium vir verbeterde groeitempo en netto opbrengs te gebruik om sodoende wins te maksimaliseer.
30
Goosen, Neill Jurgens. "Organic acids as potential growth promoters in abalone culture." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/16416.
Full textAbstract:
ENGLISH ABSTRACT: The first successful captive spawning of the South African abalone Haliotis midae occurred in
the 1980’s and subsequently the commercial abalone industry in South Africa has
developed, with an estimated investment of US$ 12 million and annual output of 500 to 800
tons by 2001, making South Africa the biggest abalone producer outside of Asia. Natural
kelp is currently the major feed and the development of a suitable substitute, and improved
disease management in abalone culture are seen as the primary factors limiting expansion of
the industry in South Africa. Further, abalone growth rates are very slow and improvements
in growth rate will lead to shortened production times with benefits to producers. Diseases in
aquaculture have traditionally been combated using antibiotics as treatment (therapeutic
usage) and preventative measure (prophylactic usage). In terrestrial livestock management,
antibiotics are also used as growth promoters. The use of antibiotics in aquaculture has
recently sparked concerns about the development of antibiotic resistance in pathogens of
humans and aquaculture organisms, and alternative strategies to using antibiotics mainly
focus on manipulating the microbial composition in the host organism, in order to establish a
beneficial microbial population to prevent disease.
The role that organic acids and their salts can play as growth promoters in the South African
abalone Haliotis midae, and as manipulators of the gut microflora of this species of abalone
was investigated and compared to the effects of antibiotics. Three different treatments were
tested against a negative control and a positive control containing 30ppm avilamycin, a
commercial antibiotic growth promoter (AGP) used in the pig and poultry industry. The 3
treatments consisted of 1% acetic and 1% formic acid (treatment AF), 1% sodium benzoate
and 1% potassium sorbate (treatment SBPS), and 1% benzoic and 1% sorbic acid
(treatment BS). Three different experiments were conducted to test the effects of the different
acids and salts. The first experiment was under controlled optimum water temperature
conditions (16.5ºC), another at elevated water temperature (20.5ºC) in order to test response
during temperature stress conditions, and the final trial was conducted under uncontrolled
practical production conditions. In an attempt to establish the mechanism by which the
treatments have their effects (if any), the composition of the gut microflora of the abalone
was monitored. It was found that the organic acids and salts investigated can enhance the growth rate of
Haliotis midae in the size class 23 mm to 33 mm mean length significantly when compared to
both control treatments. It was further found that the tested AGP had no effect on growth
rate. None of the treatments had a significant effect on feed conversion ratio (FCR),
Incidence cost (IC) or feed intake. It could also not be shown that the treatments affected the
intestinal microflora of the abalone, although this might be due to inadequate microbiological
methods. The mechanism by which the acids and salts have their effects could not be
established.
It was found that the animals in the controlled system underwent an initial adaptation period,
which led to improvement in specific growth rate (SGR), FCR and IC as the experiment
progressed during the controlled optimal conditions experiment. Large differences in FCR
and IC was seen for controlled optimal conditions and production conditions which means
that there is still a large scope for developing methods to improve practical on-farm feed
utilisation by abalone.
SGR, FCR and IC were negatively influenced by raising water temperature from 16.5ºC to
20.5ºC. The composition of the gut microflora of the abalone also changed significantly after
the water temperature was raised. It appears that animal weight gain and shell growth
respond differently to changing water temperatures, which is reflected in a change in Fulton
condition factor.
A relationship between the length and weight of abalone between 15 mm and 47 mm was
established and it was found that Haliotis midae does not follow an isometric growth
relationship. This relation can be used as a tool to improve farm management and therefore
also profitability.
Various micro-organisms were isolated from Haliotis midae during the trial, but their
relationship and interaction with abalone is not clear. Clear dominance by specific species of
bacteria was observed during certain periods.
The current research has clearly showed the potential of organic acids and their salts to act
as growth promoters in the South African abalone Haliotis midae, with application in both the
local aquaculture and feed manufacturing industries. The possibility further exists that some
aspects of the current research can be adapted to be applicable in other abalone species
and even in other aquaculture species.AFRIKAANSE OPSOMMING: Die eerste suksesvolle aanteel van die Suid-Afrikaanse perlemoen Haliotis midae in gevangeskap is in die 1980’s gerapporteer, waarna ‘n suksesvolle akwakultuur industrie ontwikkel het met ‘n geskatte produksievermoë van 500 tot 800 ton en kapitaalbelegging van US$ 12 miljoen in 2001. Suid-Afrika is tans die grootste perlemoen-produserende land wat buite Asië geleë is. Die ontwikkeling van ‘n geskikte alternatiewe voedselbron vir natuurlike kelp (tans die algemeenste voedselbron wat gebruik word in die kweek van perlemoen), sowel as verbeterde siektebestryding word tans gesien as die hooffaktore wat verdere uitbreiding in die Suid-Afrikaanse industrie beperk. Perlemoen het verder baie stadige groeitempo’s en enige verbetering in hierdie verband sal produksietye verkort en dus produsente bevoordeel. Siektes in akwakultuur word tradisioneel bestry deur gebruik te maak van antibiotiese behandeling (terapeutiese bestryding) of van voorkomende behandeling (profilaktiese bestryding). In gewone diereproduksie-sisteme (bv. varke en hoenders) word antibiotika ook gebruik as groeistimulante. Die gebruik van antibiotika in akwakultuur het onlangs die bekommernis laat ontstaan dat sekere menslike en dierepatogene weerstand kan ontwikkel teen sommige middels, wat die behoefte laat ontstaan het om siektebestryding sonder die gebruik van antibiotika te ontwikkel. Alternatiewe strategieë fokus grootliks daarop om die samestelling van die mikrobiese bevolking van die gasheer te manipuleer en sodoende ‘n voordelige bevolking in die gasheer te vestig, wat dan siektes voorkom. Daar is ondersoek ingestel na die rol van organiese sure en hul soute as groeistimulante en manipuleerders van die mikrobiese bevolking in die Suid-Afrikaanse perlemoen Haliotis midae. Drie verskillende behandelings is getoets en vergelyk met beide ‘n negatiewe- en positiewe kontrole (wat 30 dele per miljoen van ‘n kommersiële antibiotiese groeistimulant bevat het). Die drie formulasies het onderskeidelik bestaan uit ‘n mengsel van 1% etanoëen 1% metanoësuur (behandeling AF), 1% bensoë- en 1% sorbiensuur (behandeling BS) en 1% natriumbensoaat en 1% kaliumsorbaat (behandeling SBPS). Om die effekte van hierdie formulasies te toets, is daar 3 proewe gedoen. Een proef is gedoen onder temperatuurbeheerde toestande teen ‘n optimum watertemperatuur van 16.5ºC terwyl ‘n ander gedoen is onder onbeheerde, praktiese produksie-omstandighede. ‘n Verdere beheerde proef is gedoen teen ‘n watertemperatuur van 20.5ºC om die effek van die verskillende formulasies te toets wanneer die diere aan temperatuur-spanning blootgestel word. Die samestelling van die mikrobiese bevolking in die dunderm van die perlemoen is deurentyd gemonitor in ‘n poging om die meganisme vas te stel waarvolgens die sure en soute hul effek het, indien daar enige effek waargeneem word. Daar is gevind dat die onderskeie sure en suursoute die groeitempo van Haliotis midae met ‘n gemiddelde lengte van 23 mm tot 33 mm beduidend kan verhoog in vergelyking met die groeitempo’s van beide kontroles. Daar is gevind dat die antibiotiese groeistimulant geen effek het op die groei van die diere nie en dat geen behandelings ‘n beduidende effek op voeromsetting, voerkoste of voerinname gehad het nie. Daar kon nie bewys word dat enige van die formulasies of die antibiotika ‘n effek gehad het op die mikrobes in die spysverteringskanaal van die perlemoene in die sisteem nie, alhoewel die gebrek aan ‘n effek moontlik toegeskryf kan word aan die onakkurate en onvoldoende mikrobiologiese metodes wat gebruik is tydens die studie. Die meganisme waarvolgens die sure werk kon nie vasgestel word nie. Daar is verder gevind dat die diere in die temperatuur-beheerde eksperiment aanvaklik deur ‘n aanpassingsperiode gegaan het, wat tot gevolg gehad het dat die spesifieke groeitempo, voeromsetting en voerkoste verbeter het met die verloop van die eksperiment. Daar is groot verskille gevind in die voeromsetting van beheerde optimale toestande en onbeheerde produksietoestande, wat impliseer dat daar nog baie ruimte en geleenthede is om metodes te ontwikkel wat beter voeromsetting bewerkstellig tydens perlemoenproduksie. Spesifieke groeitempo, voeromsetting en voerkoste is nadelig beïnvloed toe die watertemperatuur verhoog is vanaf 16.5ºC na 20.5ºC. Die samestelling van die mikrobiese bevolking in die spysverteringskanaal van die perlemoen het ook beduidende veranderinge ondergaan tydens hierdie temperatuur verhoging. Dit wil voorkom asof die lengtegroei van die dop en die toename in massa verskillend reageer op ‘n verandering in watertemperatuur en hierdie effek word weerspieël in die verandering in Fulton-kondisiefaktor. ‘n Verwantskap tussen totale doplengte en totale gewig van Haliotis midae kon vasgestel word vir diere tussen 15 mm en 47 mm en daar is gewys dat H. midae nie ‘n isometriese groeipatroon volg nie. Hierdie verwantskap kan aangewend word tydens produksiebestuur om produksie te verbeter en daardeur ook winsgewendheid te verhoog. Verskeie mikrobes is tydens die verloop van die proef geïsoleer, maar die rol van en interaksie tussen hierdie mikrobes en die Suid-Afrikaanse perlemoen is nie duidelik nie. Sekere bakterieë het die mikrobiese bevolking in die spysverteringskanaal van die perlemoen in hierdie proef oorheers tydens sekere groeiperiodes. Die huidige navorsing het duidelik aangetoon dat organiese sure en hul soute as groeistimulante kan optree in die Suid-Afrikaanse perlemoen Haliotis midae, met toepassings in die plaaslike akwakultuur- en voervervaardigins-industrieë. Dit beskik verder oor die potensiaal om aangepas te word sodat dit toepaslik is in ander perlemoenspesies en selfs ander akwakultuur organismes.
31
Vlok, Arnoldus Christiaan. "Genetic assessment of five breeding populations of abalone (Haliotis midae) through a comparative Performance Testing Scheme." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96870.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Cultured abalone in South Africa is undomesticated. For the local industry to remain competitive on the international markets it is essential to improve production. This study is part of a selective breeding component of a larger genetic programme that aims to enhance productivity of the local industry by genetic improvement of growth rates. Selective breeding programmes are based on genetic variation and correlations. Molecular studies proved genetic differentiation exist between the broodstock- and offspring populations and among the offspring populations used in this study. Five commercial abalone farms from the Walker bay region each entered 3000 randomly selected animals obtained from synchronised mass spawning of conditioned broodstock into a Performance Recording Scheme (PRS). Microsatellite marker analysis proved these broodstock populations to be representative of the wild populations. The five cohorts were assessed over the five locations represented by three replicates per location with 200 randomly assigned animals per replicate. The average growth rate was used as growth performance parameter by measuring shell length and body weight at three month intervals over a period of 24 months. Interaction was observed between cohort and location effects when analysing the full data set. This was unexpected as the cohorts were constructed from parent stick that was randomly sampled from the same geographical area, the larger Walker bay. The factors suspected of causing this observed interaction were considered in a stepwise analysis. Initial and progressive tag loss, differences in initial size of animals entered into the study and on-farm management errors were considered as possible causes of the observed interaction in a stepwise analysis. Statistically significant differences were observed between the five cohorts and between the five locations in terms of length and weight growth rates. Based on these findings it is advised that a central facility is used to effectively compare the growth rates of different cohorts or populations. Any future research in selective breeding to follow this study should involve the integration of molecular techniques and biotechnologies.
AFRIKAANSE OPSOMMING: In Suid-Afrika is gekweekte perlemoen wild. Vir die plaaslike bedryf om op die internasionale markte kompeterend te bly, is dit noodsaaklik om produksie te verbeter. Hierdie studie vorm deel van ’n selektiewe telingskomponent van ‘n groter genetiese program met die doel om die produktiwiteit van die plaaslike bedryf deur die genetiese verbetering van groeitempo’s te verbeter. Selektiewe teelprogramme word gebaseer op genetiese variasie en korrelasies. Molekulêre studies het bewys dat daar genetiese differensiasie bestaan tussen die teel- en nageslagpopulasies en onder die nageslagpopulasies wat in hierdie studie gebruik is. Vyf kommersiële perlemoenplase in die Walkerbaaistreek het elk 3000 ewekansig geselekteerde diere vanaf gesinkroniseerde massa broei van gekondisioneerde teelpopulasies aan ‘n Performance Recording Scheme (PRS) bygedra. Mikrosatelliet merker-analise het bewys dat hierdie teelpopulasies verteenwoordigend is van die wilde populasies. Die vyf kohorte is oor die vyf liggings geassesseer, elkeen waarvan verteenwoordig is deur drie replikate bestaande uit 200 ewekansig toegedeelde diere per replikaat. Die gemiddelde groeitempo is gebruik as die groeiprestasieparameter deur skulplengte en liggaamsgewig elke drie maande oor ‘n tydperk van 24 maande te meet. Daar is interaksie waargeneem tussen kohort- en liggingseffekte toe die volledige datastel geanaliseer is. Hierdie was onverwags, aangesien die kohorte gekonstrueer is uit teelouers waarvan monsters ewekansig vanuit dieselfde geografiese gebied, naamlik die groter Walkerbaai, geneem is. Die faktore wat vermoedelik hierdie waargenome interaksie veroorsaak het, is in ‘n stapsgewyse analise beskou. Aanvanklike en progressiewe merkerverlies, verskille in die aanvanklike grootte van die diere wat in die studie ingesluit is en bestuursfoute op die plaas is as moontlike oorsake van die waargenome interaksie voorgestel. Statisties betekenisvolle verskille is tussen die vyf genotipes en tussen die vyf liggings in terme van lengte en gewigsgroeitempo’s waargeneem. Op grond van hierdie bevindings word daar voorgestel dat ‘n sentrale fasiliteit gebruik word om die groeitempo’s van die verskillende genotipes of populasies doeltreffend te vergelyk. Enige toekomstige navorsing oor selektiewe teelt wat op hierdie studie sou volg, moet die integrasie van molekulêre tegnieke en biotegnologieë behels.
32
White, Hermien Ilse. "Anaesthesia in abalone, Haliotis midae." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005059.
Full textAbstract:
The principle aim of this study was to isolate a chemical for the "safe anaesthesia" of abalone under commercial farming conditions. "Safe anaesthesia" implied that the anaesthetic had no immediate detrimental or long term sublethal effect on the abalone, that it was safe for the farmer, the consumer and the environment. Four chemicals, magnesium sulphate (MgS0₄), ethylenediamine tetra-acetic acid (EDTA), 2-phenoxyethanol and procaine hydrochloride were shown to effectively inhibit the in vitro contraction of isolated tarsal muscle of Haliotis midae. This identified them as potential anaesthetics for abalone. Since abalone, like any other aquaculture species, would be subject to frequent size-sorting during the grow-out period, size related dosage tables were developed for the four chemicals at a temperature of 18⁰C. Dosage tables were also developed for benzocaine and carbon dioxide (C0₂), Three size classes (5-15, 20-50 and 60-90 mm shell length (SL)) of abalone were considered. Only three of the six chemicals, viz. MgS0₄, 2-phenoxyethanol and CO₂, met the criteria of an effective abalone anaesthetic in that they effected rapid and mortality-free anaesthesia. The other three chemicals caused mortalities and were considered to be unsuitable for commercial scale anaesthesia. Temperature related dosage tables were then developed for MgS0₄ and CO₂, MgS0₄ concentrations and CO₂ flow rates for effective anaesthesia in abalone were found to be inversely related to temperature. The three size classes of H. midae were intermittently exposed to MgS0₄ and 2-phenoxyethanol anaesthesia for an eight month period to determine the effect of the anaesthetics on growth rate. Because of an increased resistance to the efficacy of 2-phenoxyethanol and high monthly mortalities it was concluded that this chemical was unsafe and unsuitable for commercial use. MgS0₄, on the other hand, had no effect on growth of abalone and no significant effect on the rate of mortality. MgS0₄ also had no measurable effect on H. midae muscle ultrastructure and, by implication had no effect on flesh texture. The use of MgS0₄ as an anaesthetic would, therefore, not affect marketability. Moreover, no magnesium residues were found in H. midae muscle tissue after short term or intermittent long term exposure to MgS0₄ anaesthesia. It was found that the three size classes of H. midae used in this study could be safely exposed to the recommended MgS0₄ concentrations for up to 40 minutes without any mortalities. This is more than adequate for routine farming procedures. Medium size abalone (20-50 mm SL) were also safely exposed to 14 g.100 ml⁻¹ MgS0₄ for up to 6 hours without any mortalities. The results have shown that MgS0₄ was undoubtedly the best chemical that was evaluated for anaesthesia of H. midae in this study. It fulfils the requirements set forth by the U.S.A. Food and Drug Administration (FDA) in that it is safe for the abalone, the farmer, the consumer and the environment.
33
Counihan, Regina Theresa. "Early life history of haliotis asinina : a model for haliotid aquaculture and molluscan research /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16504.pdf.
Full text
34
Vorster, Gysbert. "A quantitative genetic analysis of the effect of crossbreeding on the growth rate of the South African abalone, Haliotis midae." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/20900.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The genetic status of H. midae broodstock in the South African aquaculture industry reflects that of random samples originating from undomesticated wild populations. The nature of growth in abalone is very slow, taking between three and four years to reach a marketable size of between 60 to 100 grams. It is therefore of paramount importance to improve this trait in order to ensure global competitiveness and economic viability within the industry. Improving this negative characteristic through conventional selection methods is a long-term venture and alternative means that would yield instantaneous results had to be considered. Crossbreeding was identified as an alternative, short-term strategy to improve growth rate. A crossbreeding experiment was performed between two populations of the abalone, Haliotis midae, from the East (E) and West (W) Coast of South Africa. This was done to investigate the occurrence of heterosis for growth among the crossbred genotypes (East x West, West x East). Fifteen males and females from both the East and the West Coast populations were mated in a complete dialelle crossbreeding experiment to produce four progeny groups (WW, EE, EW and WE). Progeny groups were evaluated for weight (bW) and length gain (bL) over a specific growth period of 9 months. The results provided no evidence of significant differences in weight (P = 0.085) or length gain (P = 0.244) between the four progeny groups, giving no indication of significant heterosis for weight and length gain among the crossbred progenies of these East and West Coast populations. It is recommended that further efforts to obtain improved growth rate in the abalone, Haliotis midae, through crossbreeding only be considered in light of clear evidence of substantial genetic differentiation between such populations.
AFRIKAANSE OPSOMMING: Die huidige status van perlemoen, soos dit voorkom in akwakultuur bedrywighede in Suid Afrika, weerspieël dié van ‘n ewekansige monster vanuit wilde, natuurlike populasies. Perlemoen is inherent ‘n stadig groeiende organisme wat tussen drie en vier jaar neem om tot ‘n bemarkbare grote van 60 tot 100 gram te groei. Dit is dus uiters noodsaaklik om hierdie eienskap te verbeter ten einde die bedryf ekonomies lewensvatbaar en mededingend op wêreld markte te maak. Konvensionele seleksie as ‘n metode om hierdie negatiewe eienskap te verbeter is ‘n langtermyn onderneming wat die identifisering van ‘n korttermyn metode, wat ondmiddellike resultate lewer, noodsaak. Kruisteelt is geïdentifiseer as geskikte korttermyn oplossing aangesien dit onmiddellike resultate lewer. ‘n Kruisteel eksperiment is uitgevoer tussen twee populasies van die perlemoen, Haliotis midae, van die Ooskus (E = East) en die Weskus (W = West) van Suid Afrika. Dit is gedoen om die omvang van heterose vir groeitempo in die gekruisde nageslag (East x West, West x East) te bepaal. Fyftien mannetjies en wyfies van beide die Oos- en Weskus populasies is met mekaar gepaar in ‘n volledige dialleel kruising om vier nageslag groepe (WW, EE, EW en WE) te vorm. Die nageslag is geëvalueer ten opsigte van massa (bW) en lengte (bL) toename oor ‘n spesifieke groei tydperk van 9 maande. Die eksperimentele resultate dui daarop dat die vier nageslag groepe nie betekenisvol van mekaar verskil het ten opsigte van massa (P = 0.085) en lengte (P = 0.244) toename nie en dat daar dus geen aanduiding van heterose vir massa en lengte toename in die nageslag van kruisings tussen die Ooskus en Weskus populasies bestaan nie. Daar word aanbeveel dat kruisteling as ‘n metode van genetiese verbetering van groeitempo in Haliotis midae slegs oorweeg word in die lig van nuwe molekulêre bewyse van genoegsame genetiese differensiasie tussen sulke populasies.
35
Proudfoot, Lee-Anne. "Population structure, growth and recruitment of two exploited infralittoral molluscs (Haliotis midae and Turbo sarmaticus) along the south east coast, South Africa." Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005430.
Full textAbstract:
The two most frequently exploited species along the south east coast of South Africa are the gastropods, Haliotis midae (abalone) and Turbo sarmaticus (alikreukel). H. midae is a high valued commercial species, and suffers intense levels of illegal fishing. T. sarmaticus however, has no commercial value but is the preferred food item for impoverished subsistence communities. Owing to the fact that no legal commercial fishery exists for either species along the south coast, very few studies have been undertaken, especially in the heavily exploited infralittoral. Infralittoral size frequency distributions for both species revealed significant variation in density and size among sites of varying exploitation pressure. Densities ranged between 0 – 2.23 m⁻² (H. midae) and 0.03 – 4.93 m⁻² (T. sarmaticus) and maximum shell lengths ranged from 49.4 – 153.5 mm (H. midae) and 28.3 – 104.4 mm (T. sarmaticus). Relatively high densities and large sizes were found in marine reserves and secluded areas, and low densities and small sizes at sites near to large population centres and within the former Ciskei homeland region. Mean size of the largest 10% of the population, total density and sexually mature density were significantly related to exploitation predictors for both species. In addition, densities of H. midae juveniles were significantly related to exploitation predictors, suggesting that recruitment may be suppressed at the most exploited sites. Exploitation of T. sarmaticus tended to be localized with refuge and subtidal populations persisting. H. midae exploitation was however, far more extensive and intense. Growth of H. midae was investigated using three methods; mark-recapture, cohort analysis and growth banding analysis at Kowie Rocks, Port Alfred. The most useful of these methods for determining growth was a new technique described for growth banding analysis; which was validated using cohort analysis and measurements of shells of known age. This technique was less time consuming and labour intensive than previously described methods. Abalone growth was best described by the Schnute (1981) growth function. Systematic geographic variation in growth was observed for 10 sites along the South African coastline. Significant differences in growth among sites existed for animals between 0-4 years (P < 0.0001) and 4-6 years (P < 0.0001), and in the mean maximum sizes attained (P < 0.001). In general, abalone from the south east/east coast were found to have faster growth rates, smaller mean maximum sizes and attained sexual maturity earlier than those along the south west/ west coast. Haliotis midae recruit and juvenile densities were found to differ significantly among sites of varying exploitation pressure (P < 0.0001) and among months for recruit densities (P < 0.001). Exploited sites had low recruit and juvenile densities compared to unexploited sites and peak recruitment occurred during October/ November 2005. Recruit densities were significantly related to infralittoral adult densities during two of the three sampling months (P<0.05), when recruitment was low. No relationship was observed during the period of high recruitment, with all sites receiving high recruit densities. It was concluded that variation in recruit densities was the result of a combination of both density-dependent relationships (i.e. local spawner density and temporal variability in recruitment intensity) and the possible dispersal capabilities of H. midae. In addition, it was concluded that at present recruitment overfishing was not occurring along the south east coast. Post-recruitment mortality rates were variable but relatively constant, with hypothetical percentage survival and density curves revealing high rates and similar mortality curves among sites. Variation in juvenile densities was consequently a result of initial recruit densities and not variation in post-recruitment mortality. T. sarmaticus populations were found to be regionally sustainable and persisted along the south east coast due to adjacent intertidal and subtidal refuge populations. However, H. midae populations are becoming decimated along the south east coast. From the information obtained in this study new management proposals were suggested and discussed, such as closed areas and region-based management fisheries together with stock enhancement. These suggestions may prove to be feasible alternatives to present management strategies.
36
Simon, Carol Anne. "The life history patterns of the polychaete, Terebrasabella heterouncinata, a pest of cultured abalone." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005632.
Full textAbstract:
Terebrasabella heterouncinata is a small K-selected sabellid polychaete. It is a simultaneous hermaphrodite with a semi-continuous mode of reproduction, producing relatively few large eggs that are brooded within the parental burrow until the larvae emerge, to settle on the growing edge of the abalone shell. Despite its low fecundity, this worm has become problematic on abalone farms in South Africa. The present study was conducted to gain an understanding of the life history patterns of T. helerouncinata to determine how they contributed to the success of these worms under altered conditions. This study demonstrated that conditions prevalent on abalone farms were conducive to enhancing the reproductive success of this worm, and suggests that larger, more fecund worms may have been selected for in the decade that these worms have been present on the farms. Increased nutrient availability, and possibly the increased stability of the farm environment relative to its natural environment, has led to a 1.5-fold increase in the average size of the worms. Body size was found to be positively correlated with brood size, and this resulted in worms on farms brooding 3 to 4.5 times more offspring at a time than worms from wild abalone. The ability to increase the number of eggs produced at a time may have been limited by the fact that these worms have only two ovaries. Thus, the increase in fecundity may have been related primarily to the increase in the rate at which the eggs were laid by the worms on the farms, and the increase in the coelomic space available for the storage of these rapidly developing eggs. The ability to increase the rate at which oocytes develop may be related to the vitellogenic mechanisms employed by these worms. Vitellogenic oocytes are able to incorporate high molecular weight yolk precursors from the surrounding coelomic fluid through endocytotic activity. This may allow the oocytes to increase the rate at which they incorporate yolk material under conditions of nutrient enrichment. The increase in fecundity did not occur at the expense of offspring size and, presumably, quality. The increased reproductive output on the farms was compounded by a proportionate increase in the number of reproducing worms within the population. In addition, these worms are long-lived (worms from farmed abalone reached a maximum age of approximately 40 months) and exhibit negligible senescence. Thus, their reproductive output did not change significantly with an increase in age. Furthermore, the proportion of the reproductive worms did not decrease with an increase in age. Thus, within the age range tested, worms of all ages have the potential to make equal contributions to population growth. While diet and abalone stocking density could not be identified as having a significant effect on reproductive output and infestation rate under intensive culture conditions, it was demonstrated that in a naïve abalone population, the total intensity of infestation increased exponentially with time. This increase may be a consequence of an increase in fertilisation success. These worms continuously produce entaquasperm that are released into the water column. The sperm are collected by other individuals that then store the sperm in a single spermatheca. The ability to store sperm relieves individuals of a dependence on the synchronisation of spawning of eggs and sperm. As the population size and density increases, there could be more individuals releasing sperm into the water column, resulting in a continuous supply of sperm. The increased production of eggs would therefore not be constrained by a lack of sperm. The stored sperm are released into the brood chamber to fertilise eggs as they are laid, and this would probably increase the fertilisation success in the species. This study also provides evidence to suggest that reproduction in this worm has a seasonal component. Future studies should concentrate on measuring fertilisation success in greater detail, measuring the effect of season on reproduction, determining whether there are genetic differences between worms on farmed and wild abalone and determining whether wild worms have similar life-spans and age-related fecundity as worms on farms.
37
Shepherd, Scoresby Arthur, and mikewood@deakin edu au. "Aspects of the biology of the abalone Haliotis Laevigata and Haliotis Scalaris." Deakin University. School of Sciences, 1987. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050902.150049.
Full textAbstract:
The abalone Haliotis laevigata Donovan is commercially exploited in southern Australia; Haliotis scalaris Leach is a smaller, noncommercial species. This thesis describes the early life history of both species and other aspects of the fishery biology of H. Iaevigata required for fishery management.
Both abalone species recruit onto a crustose coralline substratum variously from spring to winter. After settlement the growth rate of both species Is linear for a number of years (1 .7mm/month for H. Iaevigata and 1.1mm/month for H. scalaris) . Crustose coralline algae are the main food during the first year of life but thereafter the diet switches largely to drift algae and seagrass. Survival of newly-settled cohorts differed between years and between species. Overall, it appeared to be density Independent at low densities but density-dependent at high densities,
Recruitment strength (measured at 2-1/2 - 3 years of age) and natural mortality of adults in a closed population was measured over 17 years at West I. There were sequences of strong and weak recruitments, but no relationship with presumed spawning stock size was apparent. Adult natural mortality rates ranged from 0.02 to 0.86 and were strongly density dependent. Stingrays were a major, and octopuses a minor, cause of mortality.
The fecundity of H. Iaevigata was investigated at a number of sites and was adequately described by linear regressions of fecundity on total weight. Fecundity ratios and growth rate differed between sites and fecundity appears subject to phenotyplc and genotypic variation.
The short and long term movement of H. laevigata was also examined, !n short term studies sexually mature Individuals aggregate during the spawning season but disperse randomly at other times of the year. In the longer term the amount of movement depends on availability of crevice space and size. Movement is also directional and, at one site, was toward that of the approaching swell.
A method is described for estimating density of abalone by using a free-range search technique and adjusting for individual variation in power and efficiency of different divers and in differing degrees of habitat heterogeneity. The method is useful for estimating recruitment strength and density of abalone in surveys of abalone stocks.
38
Henderson, Ray Arthur. "Mitigation methods for Terebrasabella heterouncinata, a problematic sabellid polychaete, populations within an abalone (Haliotis midae) production system." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/1580.
Full textAbstract:
Thesis (MPhil (Animal Sciences. Aquaculture))--University of Stellenbosch, 2006.T. heterouncinata is a sabellid polychaete endemic to South Africa and found primarily in the shells of the abalone Haliotis midae. With the intensification of abalone aquaculture around the world, T. heterouncinata has become a problematic pest by causing shell deformities, reducing abalone growth rates and, in some instances, high abalone mortalities. The problem of this sabellid was first noticed in Californian in the early 1980’s in Red abalone (Haliotis rufescens) production facilities. Many mitigation methods have been tested over the years and this paper investigates another two methods; a reduction in particulate load in the tank to reduce the food source of the sabellid which perhaps will reduce fecundity, and to use ultrasound as a possible mitigation method. This study found that filtration and reduction in suspended particles did not have a significant effect, but that ultrasound did have a significant effect in reducing T. heterouncinata populations.
39
Nicholson, Gareth Hurst. "Towards understanding the effects of stocking density on farmed South African abalone, Haliotis Midae." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1015646.
Full textAbstract:
The profitability of abalone farms is heavily influenced by their production per unit of grow-out space. With farms having physically expanded to the maximum, and with increasing production costs, one of the most realistic ways for farms to increase their production is through optimizing stocking densities. The effect of stocking density on Haliotis midae performance is undocumented and optimal stocking densities for this species have not been determined. Experiments were conducted under farm conditions to investigate the effects of four different stocking densities (16 %, 20 %, 22 % and 24 % of available surface area) on growth, production and health of three different size classes of abalone (15-35 g, 45-65 g, and 70-90 g start weight). Each treatment was replicated four times and trials ran over a period of eight months with measurements being made at four month intervals. Abalone behaviour was observed during the trials in the experimental tanks. Weight gain per abalone decreased with an increase in density for all tested size classes (5.04 ± 0.18 to 2.38 ± 0.17; 5.35 ± 0.21 to 4.62 ± 0.29; 7.97 ± 0.37 to 6.53 ± 0.28 g.abalone-1.month-1 for the 15-35, 45-65 and 70-90 g classes respectively, with an increased density of 16 to 24 %). Individual weight gain of 15-35 g abalone was similar at stocking densities of 16 % and 20 % while weight gain of 45-65 g and 70-90 g abalone decreased when density was increased above 16 %. Biomass gain (kg.basket-1.month-1) was not affected by stocking density in the 15-35 g and 45-65 g size classes (1.29 ± 0.02 and 0.97 ± 0.02 kg.basket-1.month-1 respectively). However, the biomass gained by baskets stocked with 70-90 g abalone increased with stocking density (1.08 ± 0.02 to 1.33 ± 0.02 kg.basket-1.month-1) with an increased density of 16 to 24 %) and did not appear to plateau within the tested density range (16 to 24 %). Food conversion ratio did not differ significantly between densities across all size classes. Stocking density did not have a significant effect on abalone condition factor or health indices. The proportion of abalone above the level of the feeder plate increased with density (7.26 ± 1.33 to 16.44 ± 1.33 with an increased density of 16 to 24 %). As a proportion of abalone situated in the area of the basket, the same proportions were situated on the walls above the feeder plate and on the feeder plate itself irrespective of stocking density (p > 0.05). Higher proportions of animals had restricted access to feed at higher stocking densities (p = 0.03). The amount of formulated feed available on the feeder plate did not differ between stocking densities throughout the night (p = 0.19). Individual abalone spent more time above the feeder plate at higher stocking densities (p < 0.05). The percentage of time above the feeder plate, spent on the walls of the basket and on the feeding surface was not significantly different at densities of 20 %, 22 % and 24 % (p > 0.05) but abalone stocked at 16 % spent a greater percentage of time above the feeder plate on the feeding surface (83.99 ± 6.26 %) than on the basket walls (16.01 ± 6.26 %). Stocking density did not affect the positioning of abalone within a basket during the day or at night. Different size H. midae are affected differently by increases in stocking density in terms of growth performance. Findings from this research may be implemented into farm management strategies to best suit production goals, whether in terms of biomass production or individual weight gain. The fundamental mechanisms resulting in reduced growth at higher densities are not well understood, however results from behaviour observations suggest that competition for preferred attachment space and feed availability are contributing to decreased growth rates. With knowledge of abalone behaviour at different densities, innovative tank designs may be established in order to counter the reduction in growth at higher densities.
40
Hancock, Andrew (Boze) T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." University of Western Australia. School of Animal Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.
Full textAbstract:
The Roe’s abalone (Haliotis roei) fishery near Perth, Western Australia, is uniquely accessible, and highly vulnerable to overexploitation. The sustainability of this intensively utilized fishery requires robust assessment. To facilitate an assessment, this research aimed to provide rigorous and detailed biological information with appropriate interpretation. Four critical aspects of the species’ biology and population dynamics were investigated: (1) the stock structure; (2) the recreational catch; (3) an appropriate growth curve and description of size at age; and (4) abundance measures against which to assess the impact of fishing mortality. Allozyme electrophoresis was used to investigate stock structure across the species’ distribution. Standardized variance in allelic frequencies between 10 sites in south-western Australia indicated high levels of gene flow across the 3000 km sampled (mean FST = 0.009). An isolation-by-distance was evident when pairwise measures of GST were related to geographic distance (r=0.45, P<0.001). The area of complete genetic mixing was estimated from samples within the Perth fishery to be less than the distance between the two nearest sites, or 13 km. Consequently, the Perth fishery comprises numerous discrete stocks, each requiring independent assessment. A possible mechanism for this population structure is the retention of larvae in the wind driven currents oscillating in the near-shore lagoons, with rare pulses of long distance dispersal via the southerly Leeuwin current, running further offshore. The presumed impact of intensive recreational fishing, combined with substantial commercial quotas for the Perth fishery, had led to tight restrictions on fishing effort, without any quantitative measure of the recreational catch. A stratified creel survey was adapted to estimate the effort, catch rate and mean weight of abalone harvested by the recreational sector. Catches were estimated for reef complexes, or stocks, of less than 10 nautical miles (18.5 km) of coast. Between 1997 and 2000 the recreational catch varied from 30 to 45 tonnes whole weight, approximately equivalent to the commercial quota of 36 tonnes. On average 88% of the recreational catch came from two stocks, while 98% of the commercial catch came from these two, and one additional, stocks. The incidental mortality from recreational fishing, measured as the number of abalone left dead on the reef as a proportion of the estimated catch, was approximately 7% and 20% at two sites surveyed. Spatial and temporal patterns of growth were examined on the west coast of Western Australia. Growth increments were measured for abalone larger than about 30 mm from tagging studies at five sites in the Perth fishery, a site at the northern extent of the species’ distribution and a site in the southwest. Mean annual growth increments of the 0+ year class were obtained by fitting components to length frequencies from five sites in the Perth fishery, and combined with growth increments from each Perth tag site for model fitting. A von Bertalanffy growth curve provided a slightly better fit to the tag data, but a Gompertz growth curve was a much better fit when the mean increment from the 0+ to 1+ cohort was included, with the inflection occurring at about 40 mm, the size at sexual maturity. There was no difference in annual growth between the two years studied. There was significant variation in growth between the reef platform and adjacent sub-tidal reef, but this variation was site specific and faster growth rates were not consistently associated with either habitat. There was no latitudinal trend in growth rate. Growth at the Perth sites was the fastest and similar at all five sites with growth increments greater in summer than in winter. Size and abundance of abalone were measured using fixed transects and quadrats. Abalone densities were highest on the outer edge of the platform, intermediate in the middle of the reef platform, and lowest on both the inner platform and the sub-tidal reef. The pattern of mean lengths of abalone was the inverse of the density. Mean length and abundance were driven by the presence of post-settlement juveniles on the outer and middle reef habitats. There was a high spatial variation in abundance, with densities varying between transects at the same site, but the trend between years for each transect at a site was not significantly different. Abalone abundances, by size class, were examined from sites sampled between 1996 and 2002. A low density of post-settlement juveniles at all sites in 1997 was reflected in low densities of the 1+ and 2+ year classes in subsequent years. Abalone abundances at an unfished site were steady over the seven years. Two sites were located within each of the main stocks utilised by the recreational fishery. Abundance was stable or increasing in one stock, corresponding to a stable total catch. In the second stock the total catch increased over time and abundances declined. Perth is the focus of the Roe’s abalone fishery, with recreational and commercial fishers take about equal shares of the annual catch. Stocks are highly subdivided, with most of this catch coming from only 3 stocks occupying about 20 nautical miles of coast. Growth rates were found to be lower than previous estimates, and more similar to other commercial species of abalone. All life history stages are highly habitat specific, particularly the recruits, and the distribution and abundance through time indicate that the main stocks are near, or slightly over, the limit of sustainable fishing.
41
Chalmers, Russell. "An investigation into the feeding biology and factors influencing the population dynamics of Terebrasabella heterouncinata (Polychaeta: Sabellidae), a problematic tube-dwelling polychaete in farmed abalone in South Africa." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1005136.
Full textAbstract:
Since the discovery of a new species of sabellid worm in 1993, the Californian and South African abalone industries have experienced increasing shell breakage and reduced growth rates of abalone, resulting in reduced market value of product. This polychaete worm can reach very high infestation levels. It was described as Terebrasabella heterouncinata in 1999, having originated from the South African coastline where it had been observed on several wild mollusc species. Although not a shell borer, it occupies tubes on the growing edge which are formed by deposition of nacreous shell over sabellid larvae by the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. Past research methods have not been successful in establishing effective means of eradication or control, partly due to the lack of knowledge of basic biological information on this species. This study forms the first part of an ongoing research project into the biology of terebrasabella heterouncinata. Abalone farms in South African utilise two main diets in abalone culture. An artificial formulated feed, Abfeed, is produced in South Africa and is used by the majority of farms as it increases abalone growth rate. Kelp, a natural diet of abalone, is harvested and also used as a feed. Farmers have observed higher sabellid infestation levels on Abfeed-fed abalone and suspect that diet may be an important factor influencing sabellid infestation. Abalone stocking density has also been identified as a potential factor influencing sabellid population growth on commercial farms. In order to better understand sabellid nutrition, the feeding behaviour of the sabellid in response to suspended solids of various particle size classes from both abalone diets were investigated. Both the effect of abalone diet and stocking density and their effects on sabellid morphometrics were quantified. The proximate composition and particle size distribution of suspended-solids present within kelp and Abfeed abalone raceways were also quantified. Results indicate that sabellid feeding follows no structured behavioural pattern for both abalone diets. The quantity of suspended solids in kelp raceways was greater than in Abfeed raceways (p<0.02) while there was no difference in particulate level between three abalone stocking densities (p>0.05). Protein (p<0.0001) and energy (p<0.0.1) levels of suspended solids were significantly greater in raceways dedicated to feeding Abfeed. The infestation level (number of tubes/centimetre on the grwoing edge) was significantly higher (p<0.001) in Abfeed-fed abalone. The morphometrics of the sabellids indicated that sabellids from Abfeed-fed abalone were larger in various body measurements: length (p<0.00001); neck width (p<0.001); base width (p<0.001); and surface area (p<0.001). This study suggests that abalone diet has an important influence on the infestation level and size of sabellids and that this is likely to be due to the fragmentation and leaching of nutrients from the artificially enriched commercial abalone diet.
42
Tsanigab, Salomon M. "Evaluating Namibian macrophytic algae as dietary source for South African abalone (Haliotis midae)." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1657.
Full textAbstract:
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009.An 84-day study was conducted to find a suitable diet and feeding level for the culture of South African abalone (Haliotis midae) in Namibia. Two experimental diets, namely, a seaweed diet (SWD) Laminaria pallida (macrophytic algae) and a formulated diet (FD) (macro-algae), for use in abalone (Haliotis midae) feed development, were evaluated. The animals used in this study were juveniles (24.33 ± 3.14 mm shell length; 2.72 ± 0.83 g live weight, mean ± SE) and sub-adults (58.07 ± 10.33 mm shell length and 41.96 ± 20.61 g live weight, mean ± SE). The nutrient profile of the SWD and FD displayed no differences in the protein and carbohydrate levels. Crude protein levels ranged from 4.91 to 17.68% (dry matter (DM) basis). The lipid levels in the FD (0.25%) were almost 0.56% lower than that in the SWD (0.76%). The feed conversion ratio (FCR) and protein efficiency ratio (PER) for the sub-adult abalone ranged from 2.80 to 10.90 and 0.10 to 0.40, respectively. The juvenile abalone fed on the FD yielded significantly lower (P < 0.05) FCRs (0.8) and higher PERs (1.20) than their counterparts fed on the SWD. A similar trend was observed for the sub-adult abalone although the differences were not significant (P > 0.05). The relative growth rate (RGR) of juvenile fed on the FD was 25% lower compared to those fed on the SWD, while that of the sub-adult abalone fed on the FD was 29% lower compared to the abalone fed on the SWD. From the daily growth rate (DGR) in terms of daily body weight (DGRBW) calculated after the 84-day period, repeated-measures ANOVA (RANOVA) indicated no interaction between time period and diet. Although slightly lower, the DGRBW for the juvenile abalone fed on the SWD diet (0.033 g/day) did not differ significantly from the DGRBW of abalone fed on the FD (0.079 g/day). In contrast, sub-adult abalone fed on the SWD exhibited significantly higher DGRBW compared to those fed on the FD. Although the abalone fed on the FD was slightly higher in nutritional content, there was no significantly difference (P > 0.05) in the nutritional profile of the abalone soft body tissue fed on either the SWD or FD. There was no significant (P > 0.05) difference in preference when comparing the aroma of the abalone meat samples fed on either the SWD or FD. However, there was a significant difference (P < 0.05) in the consumers’ preference in terms of flavour for the abalone sample fed on the FD. The trained taste panel results indicated that there was no difference in the aroma and flavour of the abalone fed on the different diets (P > 0.05). This study showed that cultured juvenile H. midae, readily accepted a FD, producing high consumption and survival rates. The FD still warrants further refinement and testing for it to become a more effective mariculture feed with commercial potential.
43
Foster, Gregory George. "Growth, reproduction and feeding biology of Turbo sarmaticus (Mollusca : Vetigastropoda) along the coast of the Eastern Cape Province of South Africa." Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1005391.
Full textAbstract:
Investigations were carried out on aspects of the biology of the vetigastropod Turbo sarmaticus. Studies included: 1) the distribution and standing stock of this animal at four sites along the coast of the Eastern Cape Province of South Africa; 2) the growth rate of animals on a wave-cut platform; 3) the reproductive cycle of an intertidal population; and 4) aspects of the feeding biology examining the ability of this mollusc to consume and digest six macroalgae, the influence of algal diet on growth rate and reproductive fitness and the polysaccharolytic activity of the digestive enzymes. On eastern Cape shores, T. sarmaticus had a size related distribution, with smaller animals being found towards the upper mid-shore and larger animals being found in a downshore direction. The mean shore densities of T. sarmaticus at three sites where exploitation of animals was minimal, were very similar (1.2 - 1.7 individuals/m²). The largest animals (up to 110 mm shell length) were found on an offshore island. This may have been a result of animals not being exploited, as well as a possible increase in primary productivity and food availability. The lowest density (0.2 individuals/m²) and animal size (<70 mm shell length) was recorded at a site (Kelly's beach - Port Alfred) where exploitation was more intense. It is probable that intense overexploitation was threatening the populations at this site. The growth rate of T. sarmaticus was determined by means of the von Bertalanffy growth model and expressed by the equation L[subscript]t = 81.07(l-e⁻°·⁵⁴⁴[superscript](t)). The initial growth rate of T. sarmaticus (up to ≈ 80 mm shell length) was similar on shores with different geomorphologies (i.e. boulder shores and wave-cut platforms). Growth rates of individuals were variable, which means that individuals within a population reached exploitable size (3 - 6 years old) and sexual maturity (1.5 - 2 years old) at different ages. Seasonality of reproduction of T. sarmaticus was determined using gonad index, egg diameters and spermatozoa content within the gonad. Turbo sarmaticus was dioecious and had a sex ratio in favour of males (1.2: 1). Animals attained sexual maturity at a size of about 52.5 mm shell length. There was little variation in the reproductive cycle over time with gametogenesis occurring from March/April until August/September, whilst maturity (Gonad Index = 15%) was maintained until the spawning event from December to March. After spawning the gonad regressed. Field and laboratory observations of the feeding biology of T. sarmaticus confirmed that this mollusc was a generalist grazer capable of consuming and digesting algae from the Rhodophyta, Chlorophyta and Phaeophyta. The consumption rates (juveniles: 1.45 - 9.50% body weight/day, adults: 1.06 - 6.08%) and digestibility (9 - 75% apparent dry matter) of six macroalgae was found to vary. For most algae, juvenile T. sarmaticus had higher consumption rates (1.6 - 2.8 times higher) and digestibility values (12 - 24% higher) than adults. It is suggested that consumption rates were dependent on the digestibility of the algae. In addition, it is suggested that the consumption rates of the different algae were not related to the nutritional content, but rather the energetic content of the algae. In both juvenile and adult animals, temperature had a positive influence on consumption rates, resulting in an increase at higher temperatures. However, in both juvenile and adult T. sarmaticus, algal digestibility was not affected by temperature. Finally, it was proposed that Viva rigida, Codium extricatum, Ecklonia radiata and Gelidium pristoides would provide the best nutritional value for growth and reproductive fitness in T. sarmaticus, whilst Jyengaria stellata and Corallina spp. would provide the poorest. Experiments on the effects of four algal diets on the biology of T. sarmaticus showed that the best growth rate (up to 13.8 mm shell length increase per annum), reproductive fitness (Gonad Index up to 33%) and energy levels (up to 4.76% glycogen in the foot) were achieved when T. sarmaticus was fed G. pristoides, U. rigid a or a mixed diet. Turbo sarmaticus fed Corallina spp. showed reduced growth (2.4 mm shell length increase), reproductive fitness (Gonad Index up to 4.4%) and energy levels (up to 3.42% glycogen in the foot). A study of the polysaccharolytic enzyme activity of T. sarmaticus indicated that this mollusc possesses enzymes that can, at least partially, digest most of the storage and structural polysaccharides found in the Chlorophyta, Rhodophyta and Phaeophyta. This further supported the findings that T. sarmaticus was a generalist grazer. Two levels of activity were detected: 1) high levels of enzyme activity (up to 328.2 Ilglmglmllhr)occurred on the storage polysaccharides that occur in the Rhodophyta and Chlorophyta, and 2) lower levels of activity were detected on the storage polysaccharides (up to 44.8 μg/mg/ml/hr) of the Phaeophyta and on all the structural polysaccharides tested (<45.5 μg/mg/ml/hr). It was suggested that T. sarmaticus did not rely heavily on structural carbohydrates as a source of carbon. Finally, the results of this study were discussed in relation to the future management of T. sarmaticus stocks, the possible role of this macro algal grazer in the intertidal zone and the effects of over-exploitation of this animal. The potential aquaculture of this mollusc was also addressed briefly.
44
Maliza, Siyabonga. "The use of probiotics in the diet of farmed South African abalone Haliotis midae L." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018178.
Full textAbstract:
Physiological stress in farmed abalone can lead to immunosuppression and increase the susceptibility to bacterial, viral and parasitic disease, often followed by mortality. Thus, handling and poor water quality can reduce farm production efficiency. Probiotics in aquaculture have been effective in a wide range of species in enhancing immunity, survival, improving feed utilisation and growth. Three putative probionts identified as a result of in vitro screening had been beneficial to laboratory-reared abalone in a previous study. The aim of this study was to produce an abalone feed that contains a suite of probionts that may promote abalone growth and health under farming conditions. The objectives were to compare growth and physiological responses (i.e., haemocyte and phagocytosis counts) of abalone fed a commercial feed (Abfeed®S 34, Marifeed, Hermanus) supplemented with probiotics (i.e., the probiotic diet) to abalone fed the commercial feed without probiotic supplementation as a control treatment in a factorial design with handling method as an independent variable. This experiment was conducted at HIK Abalone Farm (Pty Ltd) for a period of eight months with initial weight and length 36.1 ± 0.05 g and 58.6 ± 0.06 mm abalone-1. Another experiment was carried out at Roman Bay Sea Farm (Pty) Ltd with initial weight and length 34.7 ± 0.17 g and 62.3 ± 0.18 mm abalone-1, but this experiment included one factor only, i.e. the presence and absence of the probionts in the feed. At HIK there was no significant interaction between diet and handling on average length and weight gain month-1 after four (p=0.81 and p=0.32) and eight (p=0.51 and p=0.53) months, respectively. Average length (additional handling = 73.9 ± 0.52 mm, normal farm handling = 75.8 ± 0.57 mm) and weight gain (mean: additional handling = 68.5 ± 1.20 g, normal farm handling = 74.3 ± 1.86 g) increased significantly in animals that were handled under normal farm procedure and were either fed probiotic or control diet after eight months (p=0.03 and p=0.02, respectively). There was no iii difference in length gain or weight gain of abalone fed the probiotic diet and those fed the control diet (ANOVA: F(1,16)=0.04, p=0.84; F(1,16)=0.14, p=0.71, respectively). After four months phagocytotic count was significantly different between dietary treatments with mean values of 74.50 ± 10.52 and 63.52 ± 14.52 % phagocytosis count per sample for the probionts and control treatment, respectively (p=0.04), there was no difference after eight months at HIK Abalone Farm. There was no effect of stressor application (p=0.14) and no interaction between dietary treatment and stressor application for this variable i.e., phagocytosis count (p=0.61). There was no difference in feed conversion ratio between treatments with values ranging from 2.9 to 3.8. At Roman Bay Sea farm, there was no significant difference in mean length gain between abalone fed the probiotic and control diet after eight months (repeated measures ANOVA: F(4,28)=16.54. Mean weight gain of abalone fed the probiotic diet was significantly greater than those fed the control diet after eight months (repeated measures ANOVA: F(4,28)=39.82, p(0.00001). There was no significant difference in haemocyte counts between animals fed either probiotic or control diet after four and eight months at Roman Bay Sea farm (p>0.05).
45
Hancock, Andrew T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." Connect to this title online, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068/.
Full text
46
Donovan, Deborah Anne. "Energetics of activity in the abalone, Haliotis kamtschatkana." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ27132.pdf.
Full text
47
Lin, Albert Yu-Min. "Structural and functional biological materials abalone nacre, sharp materials, and abalone foot adhesion /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3307734.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed July 28, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 192-202).
48
Gruenthal, Kristen Marie. "Conservation genetics of California abalone species." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3268587.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed September 4, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
49
James, Darren Stuart, and mikewood@deakin edu au. "Environmental site assessment for abalone ranching on artificial reef." Deakin University. School of Biological and Chemical Sciences, 2005. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060914.100744.
Full textAbstract:
This study investigated the feasibility of ranching the abalone Haliotis rubra (Leach) and Haliotis laevigata (Donovan) on concrete artificial reefs at a site chosen by industry investors on silty bottom off Altona Beach, Port Phillip Bay, Victoria, Australia. The study started from the premise that artificial reef deployment combined with abalone stock enhancement may achieve the dual purpose of habitat and stock improvement. It evaluated the hydrodynamics of the site in relation to artificial reef structural stability and drift algal transport, the development and ecology of the artificial reef assemblage, and abalone enhancement by seeding the reefs with hatchery juvenile abalone and transplanting adult broodstock abalone.
Despite a scarcity of reports on culturing abalone on artificial reef, a literature review examined broadly the functions of artificial reefs, particularly in the context of abalone enhancement, and the relationship between artificial reefs, hydrodynamics and ecology. The major finding was that the success of artificial reef projects is highly dependent on the environment of the chosen site, and that preliminary studies are essential to predict their likely success. This consideration alone provided strong justification to undertake this study.
The topography at the Altona site was generally flat, with natural patches of low basalt boulder reef, offering low habitat complexity, yet supporting a diverse range of flora and fauna, including a low-density wild stock of H. rubra. Water depth was a mean of 3.3 m at low tide and 4.4 m at high tide.
A single, uncomplicated, concrete artificial reef of H-shape design, was tested as abalone habitat.
The hydrodynamic analysis confirmed previous studies of Port Phillip Bay, with mild current speeds
of mean 0.045 m.s-1, and maximum-modelled wave height (H1/3) of 1.21 m and period (T1/3) of 4.51 sec. Water temperature ranged from 9.9ºC during July to 23.8ºC during January, with salinity averaging of 35.5 ppt. The site had a low probability of receiving drift algae, necessary as a food source for abalone, because of its geographic location, potentially affecting ranch productivity.
Ecological monitoring of the three-year old artificial reef shows complex changes in the flora and fauna over time, particularly in respect of the sessile fauna. Key differences between the artificial reef and a nearby natural reef community were: lower cover of corallines and late colonisers, such as sponges. High levels of sedimentation were recorded at the Altona site.
Hatchery juvenile H. laevigata, with mean survival of 15% after two years and a mean annual growth rate of 39 mm, showed the most promise for outplanting. In comparison, for hatchery juvenile H. rubra, mean survival was 9% after three years and mean annual growth rate was 22 mm. No natural recruitment of H. laevigata was recorded on artificial reef despite transplants of adult broodstock on the reefs. Natural recruitment of H. rubra was also low and insufficient to reliably contribute to abalone ranch stock.
Having examined the hydrodynamic, ecological and enhancement attributes of the Altona site, the study concluded that the site was marginally viable for abalone ranching, and that an alternative site near Werribee, 20 km further southwest, had superior attributes for growth and survival of abalone.
50
Dale, Kuys Ruth. "Linkage disequilibrium in the South African abalone, Haliotis midae." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97991.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Linkage disequilibrium (LD) is defined as the non-random association of alleles at two or more loci within a population. It is sensitive to a variety of locus-specific- and demographic factors, and can thus provide much insight into the micro-evolutionary factors that have shaped species of interest. It can also be exploited to identify the genomic regions determining complex traits of interest, which can then be applied as performance evaluation markers in marker-assisted selection (MAS). The South African abalone, Haliotis midae, supports a rapidly developing aquaculture production industry, in which genetic improvement potential is high. This species also represents an opportunistic model for studying the effects of early domestication in a shellfish species. The aim of this study was therefore to quantify and characterise levels of genome-wide LD within the South African abalone, and to demonstrate its utility within population genetic investigations and the characterisation of complex traits. Estimates of LD between 112 mapped microsatellite markers within wild and cultured H. midae revealed that levels of LD in abalone are high relative to other aquaculture species. This was attributed primarily to small effective population sizes produced by a combination of natural- and anthropogenic factors. The decay of LD with genetic distance was evident in both cultured cohorts, but almost absent in wild cohorts, likely reflecting the differences in size, age and sampling of wild populations relative to cultured. Putative evidence for the effects of recombination, selection, and epistasis were also evident in distinctive locus-specific patterns of LD on some of the linkage groups, many of which could represent the effects of domestication. The effects of selection associated with the domestication event were further investigated using a candidate locus LD mapping approach to determine the proportion of candidate loci under selection associated with artificial selection for faster growth rate in cultured abalone. Two loci (15%) were found to be significantly associated with differences in size of individual animals, both of which could be linked with genes potentially involved in growth and development. These markers could therefore find application in MAS programmes for abalone. Several promising candidates for natural selection were also identified based on similarity with known genes. As the latter represented the majority, natural selection, rather than artificial selection, appears to be predominant during the early stages of domestication in abalone. While some conclusions within the current study were speculative, both the direct and indirect applications of LD were clearly demonstrated. Linkage disequilibrium data can provide a unique perspective on many of the commonly used population genetic estimates, and is therefore of great value in population genetic investigations. Furthermore, these results also highlighted the effectiveness of the candidate locus approach in species with both limited molecular resources and extensive LD.
AFRIKAANSE OPSOMMING: Koppelingsonewewig (KO) word gedefinieer as die nie-lukrake assosiasie van allele by twee of meer lokusse binne 'n populasie. Koppelingsonewewig is sensitief vir 'n verskeidenheid van lokus-spesifieke- en demografiese faktore, en kan dus insiggewend wees m.b.t. mikro-evolusionêre faktore wat spesies van belang beïnvloed het. Dit kan ook benut word om die genoom-gebiede onderligend tot komplekse eienskappe te bespeur; wat dan aangewend kan word vir prestasie-evaluering m.b.v. merkerbemiddelde seleksie (MBS). Die Suid-Afrikaanse perlemoen, Haliotis midae, ondersteun 'n vinnig ontwikkelende akwakultuur produksie bedryf, waarin genetiese verbeteringspotensiaal hoog is. Hierdie spesie verteenwoordig ook 'n opportunistiese model vir die bestudering van die gevolge van vroeë domestiseering in 'n skulpvis spesie. Die doel van hierdie studie was dus om vlakke van genoom-wye KO binne die Suid-Afrikaanse perlemoen te kwantifiseer en te karakteriseer, en om die toepassing hiervan binne populasiegenetiese ondersoeke en die karakterisering van komplekse eienskappe te demonstreer. Ramings van KO tussen 112 gekarteerde mikrosatelliet-merkers binne wilde en gekultiveerde H. midae het aan die lig gebring dat die vlakke van KO in perlemoen hoog was, in vergelyking met ander akwakultuur spesies. Dit word hoofsaaklik toegeskryf aan klein effektiewe populasiegroottes wat deur 'n kombinasie van natuurlike- en antropogeniese faktore teweeg gebring word. Die verval van KO met genetiese afstand was duidelik waarneembaar in gekultiveerde kohorte, maar amper afwesig in die wilde kohorte, waarskynlik a.g.v. verskille in populasiegrootte, ouderdom, en streekproef-neemings metodieke van die verskeie populasies. Vermeende bewyse vir die gevolge van rekombinasie, seleksie en epistase kon ook gesien word a.g.v. lokus-spesifieke patrone van KO op sommige van die koppelingsgroepe, moontlik ‘n gevolg van domestisering. Die gevolge van seleksie wat verband hou met die domestiseringsgebeurtenis is verder ondersoek m.b.v 'n kandidaat-lokus KO karteringsbenadering om die verhouding van kandidaat lokusse wat geassosieer is met kunsmatige seleksie (vir vinniger groeikoers in perlemoen) te bepaal. Twee lokusse (15%) was beduidend geassosieer met verskille in grootte tussen individuele diere. Beide van die lokusse was gekoppel met gene wat potensieel betrokke is by groei en ontwikkeling. Hierdie merkers kan dus moontlik aangewend word in MBS programme vir perlemoen. Verskeie belowende kandidaat lokusse vir natuurlike seleksie is ook geïdentifiseer gebaseer op ooreenkoms met bekende gene. Gegewe dat die laasgenoemde die meerderheid van die merkers verteenwoordig, kan daar afgelei word dat natuurlike seleksie, eerder as kunsmatige seleksie, oorheersend is in die vroeë stadia van domestisering in perlemoen. Terwyl sommige gevolgtrekkings binne die huidige studie spekulatief was, is beide die direkte en indirekte toepassings van KO duidelik gedemonstreer. Koppelingsonewewig-data kan 'n unieke perspektief gee op baie van die algemeen gebruikte populasie genetiese skattings, en is dus van groot waarde in populasie genetiese ondersoeke. Verder demonstreer hierdie resultate ook die doeltreffendheid van die kandidaat lokus benadering in spesies met beide beperkte molekulêre hulpbronne en uitgebreide KO.