Academic literature on the topic 'Abalone culture'

Nusa Penida island is one of center for seaweed culture in Bali province. Seaweed that cultured is Euchema spinosum and Euchema cottoni spread around coastal. There also found wild seaweed, such as Ulva sp and Gracillaria sp. Abalone (H. squamata) is one of kind Mollusca which high economic value, but abalone cultured is not yet develop in Nusa Penida island, although this island have high potency for developing abalone culture. Abalone culture needs seaweeds as a diet. The abundance of seaweeds as abalon diet is important for developing abalon culture in Nusa Penida Island in the future. The aim of this research was to asses the potency of seaweeds as diet for developing abalone culture in Nusa Penida island. Research was done in Batununggul village, Nusa Penida Island. Experimental design was used Completely Randomized Design (CRD) with 3 treatments and 3 replications. The treatments were used different seaweeds as diet for abalone culture: (DG=Diet Gracillaria sp, DS=Diet Spinosum sp. and DU=Diet Ulva sp.). Abalon were cultured for 4 months by feeding the diet at satiation. Data analysis was used analysis varian (Anova) with SPSS. 16. The result showed abalon fed with Gracillaria sp (DG) at 4.73 g was the highest growth by 4.73 g, followed DU by 3.93 g and DS by 3.43 g. Meanwhile the abalon shell length fed with Gracillaria sp (DG) was the highest growth by 6.55 mm, followed DU by 5.97 mm and DS by 5.60 mm. Based on variant analysis showed growth performance (length shell and weight) abalon, all treatments were not significantly different (P>0.05). The conclusion this research, the three species of seaweed can be used as diet for abalone culture. These seaweeds have same potency as diet for developing abalone culture in Nusa Penida Island

Abalone is a herbivore marine animal which feeds on seaweed. Abalone culture has a good prospect in terms of price, market share and simple culture technique. Thus, a study was conducted with the aim of finding out an effective and efficient abalone culture technique in terms of feed use and density. In this study, a 42 cm diameter plastic container with a 22 cm height was used. Three vertically arranged containers were used as the experimental group which were put into a net box and hung onto a raft so that the containers were placed in a 4 m depth below the sea surface. The juvenile of abalones being used came from a hatchery production that has been adapted to cages environment with Gracilaria sp. and Ulva sp. feed. The initial density of abalones was 450 for each container, with the initial weight of 2.6-3.2 g and the 2.5-2.7 cm shell lengths. The abalones were fed with Gracilaria sp. and Ulva sp. seaweeds with different Gracilaria sp./Ulva sp. proportions, i.e. 100/0% (A); 80/20% (B); and 60/40% (C) as the treatments. Each treatment consisted of two replications. After three months of rearing period, densities of abalones were reduced to be 190 for each experimental unit. Weight and shell length of abalones were measured every month by measuring 25 abalone samples from each experimental unit. The result of the experiment showed that the increase in the Ulva sp. proportion in the feed increased the growth of abalones and decreased the feed conversion. Feeding with Gracilaria sp./Ulva sp. proportion of 60%/40% allowed the best growth of abalones. The decrease of abalone density in the experimental unit after three months of rearing also produced an increase in their growth.

Information about abalone growth is necessary to overcome the abalone culture sustainability. Water quality parameters are aspects that need to be reviewed, one of which is the calcium level in the water. The aim of this study was to determine the optimal calcium dose in recirculation system for abalone (Haliotis squamata) growth. The study was conducted with an experimental method with four treatments (calcium oxide with doses of 0, 15, 30, 45 mg/L) and three times replications. Abalone with 2.3 g body weight, 2.3 cm shell length, and 1.2 cm shell width was reared for 60 days in recirculation system and fed with Gracilaria verrucosa. The results showed that the best abalone treatment medium with the addition of calcium oxide to increase the abalone seed production was 15 mg/L CaO with 100% survival rate, 31.57±2.82% feed efficiency, and 0.56±0.06%/day specific growth rate. Keywords: Abalone, calcium, organ composition, production, recirculation ABSTRAK Informasi tentang pertumbuhan abalon diperlukan untuk mengatasi keberlanjutan budidaya abalon. Parameter kualitas air merupakan aspek yang perlu ditinjau. Kadar kalsium dalam air menjadi salah satu aspek yang dapat ditinjau.Tujuan dari penelitian ini adalah menentukan dosis kalsium optimal melalui sistem resirkulasi untuk pertumbuhan abalon Haliotis squamata. Penelitian ini dilakukan dengan metode eksperimental dengan empat perlakuan 3 ulangan penambahan CaO dengan dosis 0, 15, 30, dan 45 mg/L. Secara singkat, abalon dengan bobot badan 2,3 g, panjang cangkang 2,3 cm dan lebar cangkang 1,2 cm dipelihara selama 60 hari dengan sistem resirkulasi dan diberi makan dengan Gracilaria verrucosa. Hasil penelitian menunjukkan bahwa media perlakuan abalon dengan penambahan kalsium oksida terbaik untuk meningkatkan produksi abalon adalah CaO 15 mg/L dengan tingkat kelangsungan hidup 100%, efisiensi pakan 31,57 ± 2,82 %, dan laju pertumbuhan spesifik harian 0.56 ± 0.06%/hari. Kata kunci: Abalon, kalsium, komposisi organ, produksi, resirkulasi

In October 2017, the Department of Primary Industries and Regional Development of Western Australia (WA) promulgated a new regulation on recreational abalone harvesting. A notable change was that, from 2017 on, the annual fishing season in the West Coast Zone was reduced to four days, from every December on Saturdays only. During the last decade, WA’s abalone fishing regulations have been overhauled frequently because of depleting local stocks. Worldwide, the marine heatwave resulting from climate change and illegal overfishing are considered the two principal reasons for abalone’s decline. Today, the highly lucrative abalone market has attracted more participants in recreational fishing in Perth, WA. Based on Asian natural heritage traditions and employing a multispecies sensory ethnographic methodology, this article provides an in-depth case study of the interaction between the local Chinese diaspora and the environment as represented in abalone harvesting practices. Between 2014 and 2016, the authors conducted one-on-one and focus group interviews with Chinese immigrants to Perth, WA, and also participated in abalone harvesting. The analysis reveals a suite of environmental influences on local Chinese diasporic life through heterogeneous forms of interaction between abalone and Perth-area Chinese immigrants.

Teknologi budidaya abalon telah tersedia dan dilakukan dengan berbagai metode budidaya pendederan dan pembesaran. Namun, hingga saat ini belum berkembang di masyarakat karena kurangnya minat pengusaha/pembudidaya abalon untuk mengaplikasikan secara komersial. Hal ini disebabkan oleh kualitas dan kuantitas benih belum stabil, pertumbuhan lambat, biaya tinggi, dan memerlukan waktu pemeliharaan lebih lama. Oleh karena itu, perlu diupayakan metode yang lebih sederhana dengan biaya murah untuk pembesaran abalon. Penelitian ini bertujuan untuk membandingkan pertumbuhan dan produksi abalon dengan padat tebar berbeda pada sistem-sistem tangki air mengalir. Benih abalon dipelihara di bak beton ukuran 12 m x 0,8 m x 0,8 m; kepadatan 70% dan 80% dari luasan dasar bak. Sementara untuk menghitung kelayakan usaha, rumus yang digunakan adalah revenue cost ratio (R/C). Hasil penelitian menunjukkan bahwa pertumbuhan panjang, lebar dan bobot cangkang pada densitas 70% lebih baik dibandingkan dengan densitas 80%. Kepadatan 70% menghasilkan 8,98% peningkatan hasil biomassa dan kematian 6,51% lebih tinggi dari kepadatan 80%. Berdasarkan analisis ekonomi, sistem pembibitan ini layak secara ekonomi di mana padat tebar 70% dari total luas dasar memiliki keuntungan finansial terbaik.Breeding technology for abalone is available, and its farming can be done using different nursery and grow-out methods. However, abalone farming has not yet been commercially practiced due to the lack of interest from fish entrepreneurs/fish farmers. This is due to several factors related to the quality and quantity of seeds, such as inconsistent availability, slow growth, high cost, and long culture was period. Therefore, it is necessary to develop a simpler and inexpensive method to culture abalone. This research aimed to improve the rearing technique for abalone. Two concrete tanks of 12 m x 0.8 m x 0.8 m in size were used in which abalone seeds were stocked with stocking densities of 70% and 80% of the bottom area. The concrete tanks were equipped with a flow-through water circulation system. The business feasibility of the culture system was calculated using the revenue cost ratio (R/C) formula. The results showed that the growth in length, shell width and weight at a density of 70% was better than that of the density of 80%. The density of 70% resulted in an 8.98% increase in biomass yield and a 6.51% mortality higher than a density of 80%. Based on the economic analysis, this nursery system is economically feasible where the stocking density of 70% of the total bottom area has the best financial return.

Australian abalone aquaculture is characterised by a prolonged culture period and slow and variable growth, and abalone is cultured in fluctuating water temperatures ranging between 10 and 25°C with distinct seasons. Temperature is a crucial environmental factor influencing abalone’s physiology and energetics, leading to a change in nutritional requirements. However, feeds are generally formulated to match the nutritional requirements at their optimal temperature. Hence, there is a need to optimise dietary protein levels to match temperature-specific requirements during extreme conditions (winter and summer). Given this, a growth trial evaluating five experimental feeds consisting of graded protein inclusion levels (320, 350, 380, 410, and 440 g·kg−1) was conducted on subadult hybrid abalone (Haliotis rubra × H. laevigata) at three different temperatures reflecting winter (12°C), summer (22°C), and the annual average water temperature (17°C) for 143 days. At lower water temperature (12°C), there was a marginal improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1. However, at higher water temperatures (when the culture water temperature is above 17°C), there was a significant improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1 as evidenced by an improved weight gain, specific growth rate, and feed conversion ratio. Furthermore, increasing dietary protein levels did not compromise the nutritional quality of the abalone tissue at all three tested temperatures. Therefore, during periods of higher water temperatures, feeding Australian hybrid abalone with a relatively high dietary protein level (410 g·kg−1) is expected to result in improved growth, shorter culture duration, and profit maximisation.

Abalone aquaculture attracts wide attention nowadays because of its high market value and depleted of wild stocks. China and Japan are the main producer of abalone from aquaculture followed by other countries such as New Zealand, Australia and US. Most of cultured abalone are temperate species but considerable research efforts have been made to culture tropical abalone in the Philippines, Thailand, and Indonesia. Most of abalone culture still depends on natural food but recent studies have been conducted to develop artificial diet for abalone. This will not only reduce wild harvest of macrolagae but also develop high nutrition diet at low cost. Successful abalone aquaculture is determined by correct nutrition supplement in the diet. As other cultured animal, abalone requires balanced nutrition of carbohydrate, protein, lipid, vitamins, and minerals. As herbivores, abalone can utilize carbohydrate efficiently as energy source and thus only requires low level of protein (range from 27%—40%). Lipid requirements range from 3%—5% while some minerals such as calcium and phosphorus in artificial feed are only needed in small amount, 0.5% of calcium in diets and 0.7% of phosphorus in the diet can improve the growth rate of abalone. There is not available information of vitamin upplementation in the diet but it is suggested that natural food meets the requirement.

This research was conducted at Geger Beach, Nusa Dua, Bali for 60 days. The purpose of this study was to find out the ratio of abalone growth rate (Haliotis squamata) to co-cultured and monoculture cultivation systems in Geger Beach waters, Nusa Dua, Bali, knowing that abalone stocking densities were more effective in culture systems and knowing more abalone stocking densities effective on monoculture systems. The method used uses the Complete Randomized Design (CRD) method which consists of four treatments with each treatment there are three repetitions. The treatment of Haliotis squamata abalone shells which is integrated with dense stocking differs from planting the same seaweed. The test animals were stocked with each basket with a density of 40 tails and 20 tails. The food given for abalone is cotoni sp. which is where seaweed cotoni sp. obtained from cultivation. Based on the comparison of the growth rate of abalone (Haliotis squamata) in co-culture and monoculture cultivation in terms of abalone length with stocking density 20 of the co-culture cultivation system obtains the highest length value of 2.50%, while the co-culture cultivation system with stocking density 40 gets the value the highest is 4.19%. At the weight of the Haliotis squamata abalone with the co-culture cultivation system at 20 stocking densities, the highest value was 0.04% and 40 highest stocking densities on the co-culture system at 1.04%. At the length of the abalone Haliotis squamata with 20 thick stocking monoculture systems got the highest value of 7.63%, while the highest stocking density of 40 was 1.28%. On abalone weight monoculture system with 20 density has the highest value of 2.67%, while 40 density has the highest value of 0.48%.

Seaweed is a commodity that has high economic value and benefits. The implementation of seaweed cultivation is quite short and the export market opportunities are wide open because the need for seaweed is quite large. This study aims to determine the growth rate of seaweed with monoculture and polyculture cultivation systems and the survival rate of abalone in polyculture cultivation. The research used an experimental method with Completely Randomized Design (CRD) consisting of two treatments and three replications. The cultivation system in this study was seaweed monoculture Eucheuma cottonii with an initial weight of 100 gr and 100gr seaweed polyculture with abalone Haliotis squamata, each polyculture culture net bag containing 50 abalones. The value of the specific growth rate of monoculture seaweed was 2.21%/day, lower than the specific growth rate of polyculture, which was 3.61%/day. T-test analysis showed the value of sig = 0.049 < = 0.05, which means that there is a significant difference between the treatment of monoculture cultivation and polyculture cultivation. The abalone growth rate value ranged from 0.78-0.91%/day and the abalone survival rate ranged from 68-76%. Changes in environmental conditions affect the condition of abalone and seaweed so that the survival value of abalone is quite low and seaweed is infected with an ice-ice disease which causes a decrease in seaweed weight gain in the final week of the study period.

Aquatic animals cannot synthesize carotenoids, thus they must come from diet or from symbionts. Previous studies have found that orange-muscle abalones are rich in carotenoids, but the effects of different diets on the accumulation of carotenoids are unknown. In this study, the effects of macroalgae (Gracilaria lemaneiformis), fresh and dried kelp (Laminaria japonica) on the contents of the predominant carotenoids, including zeaxanthin, β-carotene, and fucoxanthin, between the common and orange-muscle mutant of Haliotis gigantea were compared through a one-year culture experiment. Our study confirmed that carotenoids in abalones mainly come from diets, and the carotenoid types in the muscles were similar to their diets. We also found that feeding on G.lemaneiformis played an important role in maintaining a stable carotenoid content over time, especially zeaxanthin in H.gigantea. Our data also provided that abalones had a good growth performance under the feeding conditions of G.lemaneiformis. Finally, compared with common abalones, orange-muscle abalones had a notably enhanced ability to accumulate carotenoids through their diet, especially zeaxanthin ( P < 0.01 ). However, the growth performance of orange-muscle abalones was lower than those of common abalones fed the same diets. These results inferred that the content of carotenoid in abalone may be controlled by genetic factors, and diet had a significant influence on the accumulation of carotenoid in abalone to some extent.

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.

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.

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.

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...

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.

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.

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.

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.

The major bottlenecks in rearing the highly priced gastropod abalone (Haliotis spp.) are the slow growth rate and the high mortality during the first 8 to 12 weeks following metamorphosis and settling. The most likely reason flor these problems is related to nutritional deficiencies in the diatom diet on which the post larvae (PL) feed almost exclusively in captivity. Higher survival and improved growth rate will reduce the considerable expense of hatchery-nursery resisdence time and thereflore the production costs. BARD supported our research for one year only and the support was given to us in order to prove that "(1) Abalone PL feed on encapsulated diatoms, and (2) heterotrophic diatoms can be mass produced." In the course of this year we have developed a novel nutrient delivery system specifically designed to enhance growth and survival of post-larval abalone. This approach is based on the sodium-alginate encapsulation of heterotrophically grown diatoms or diatom extracts, including appetite-stimulating factors. Diatom species that attract the PL and promote the highest growth and survival have been identified. These were also tested by incorporating them (either intact cells or as cell extracts) into a sodium-alginate matrix while comparing the growth to that achieved when using diatoms (singel sp. or as a mixture). A number of potential chemoattractants to act as appetite-stimulating factors for abalone PL have been tested. Preliminary results show that the incorporation of the amino acid methionine at a level of 10-3M to the sodim alginate matrix leads to a marked enhancement of growth. The results ol these studies provided basic knowledge on the growth of abalone and showed that it is possible to obtain, on a regular basis, survival rates exceeding 10% for this stage. Prior to this study the survival rates ranged between 2-4%, less than half of the values achieved today. Several diatom species originated from the National Center for Mariculture (Nitzchia laevis, Navicula lenzi, Amphora T3, and Navicula tennerima) and Cylindrotheca fusiformis (2083, 2084, 2085, 2086 and 2087 UTEX strains, Austin TX) were tested for heterotrophic growth. Axenic colonies were initially obtained and following intensive selection cycles and mutagenesis treatments, Amphora T3, Navicula tennerima and Cylindrotheca fusiformis (2083 UTEX strain) were capable of growing under heterotrophic conditions and to sustain highly enriched mediums. A highly efficient selection procedure as well as cost effective matrix of media components were developed and optimized. Glucose was identified as the best carbon source for all diatom strains. Doubling times ranging from 20-40 h were observed, and stable heterotroph cultures at a densities range of 103-104 were achieved. Although current growth rates are not yet sufficient for full economical fermentation, we estimate that further selections and mutagenesis treatments cycles should result in much faster growing colonies suitable for a fermentor scale-up. As rightfully pointed out by one of the reviewers, "There would be no point in assessing the optimum levels of dietary inclusions into micro-capsules, if the post-larvae cannot be induced to consume those capsules in the first place." We believe that the results of the first year of research provide a foundationfor the continuation of this research following the objectives put forth in the original proposal. Future work should concentrate on the optimization of incorporation of intact cells and cell extracts of the developed heterotrophic strains in the alginate matrix, as well as improving this delivery system by including liposomes and chemoattractants to ensure food consumption and enhanced growth.