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Dissertationen zum Thema „Freshwater fish“
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1
Henriksson, Anna. „Biotic resistance in freshwater fish communities“. Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110251.
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Invasions of non-native species cause problems in ecosystems worldwide, and despite the extensive effort that has been put into research about invasions, we still lack a good understanding for why some, but not other, communities resist these invasions. In this doctoral thesis I test hypotheses on biotic resistance using a large dataset of more than 1000 both failed and successful introductions of freshwater fish into Swedish lakes. We have found that the classic species richness hypothesis is a poor descriptor of introduction success because it fails to acknowledge that resident species contribute to the resistance in different ways. We developed a new measure of biotic resistance, the weighted species richness, which takes into account that the resident species contributes to the resistance with different strength and sign. Further, we correlated performance traits of species in their role as an invader and as a resident species to predict how the biotic resistance of these communities would develop over time. We found a positive correlation between performance traits: Some species have high introduction success, they make a large contribution to the resistance, and they cause extinctions when introduced but do not go extinct themselves when other species establishes, whereas other species are weak performers in these respects. Thus, the biotic resistance of these communities should grow stronger as non-native species accumulates. These results give us clues about what type of communities that should be most sensitive to further invasions, i.e., communities harboring species weak performers. My results show that the biotic resistance of communities is an important factor in determining invasibility of a community. They also show that methods for quantifying resistance must take into account how interactions are structured in nature. What determine the biotic resistance of a community is the type of interactions that the resident species have with the invader and not the species richness of the community.
2
Carden, Kerilynn M. „Macrophytes as fish habitat : the role of macrophyte morphology and bed complexity in fish species distributions /“. Link to abstract, 2002. http://epapers.uwsp.edu/abstracts/2002/Carden.pdf.
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3
Lee, Ching-man. „Epidemiology of laribacter hongkongensis in freshwater fish /“. View the Table of Contents & Abstract, 2005. http://sunzi.lib.hku.hk/hkuto/record/B3149447X.
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4
Olden, Julian David. „Predictive models for freshwater fish community composition“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ54206.pdf.
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5
Lee, Ching-man, und 李靜敏. „Epidemiology of laribacter hongkongensis in freshwater fish“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45010213.
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6
Benejam, Vidal Lluís. „Fish as ecological indicators in Mediterranean freshwater ecosystems“. Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7873.
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Podeu escriure el text directament o arrossegar-lo des d'un altre documentL'objectiu d'aquesta tesi és contribuir a l'ús dels peixos continentals com a indicadors de l'estat ecològic a la conca Mediterrània. En el primer treball es va detectar que encara que tots els índex biològics estaven correlacionats significativament, els peixos integren i expressen els estressos de manera i a una escala diferents, aportant una informació complementària als altres índexs. Al segon article es van estudiar els cabals de sis conques catalanes. S'ha mostrat que els règims hídrics estan alterats amb una tendència a la disminució del cabal i del nivell dels aqüífers. S'ha detectat quatre mètriques de peixos que es troben significativament afectades en zones més castigades per manca d'aigua degut a l'activitat humana. Es discuteix la necessitat de conèixer en profunditat el règim hídric de cada conca abans d'utilitzar els índex biològics. Al tercer article es va detectar que la composició d'espècies capturades va variar significativament al llarg del buidat amb un augment de l'alburn (A. alburnus) a les aigües pelàgiques durant els dies de pitjor qualitat de l'aigua, confirmant que l'alburn és més tolerant a la mala qualitat de l'aigua que la madrilleta vera (R. rutilus) i suggereix el seu potencial com a bioindicador. La condició d'aquestes dues espècies va canviar significativament al llarg del buidat de manera molt estreta amb la qualitat de l'aigua. Al quart capítol es va estudiar la biologia dels peixos d'un embassament altament contaminat (Flix). El percentatge de DELT anomalies i la presència de paràsits externs era major en la zona impactada que als punts de control i els valors més alts de pes eviscerat i pes del fetge estaven als punts de control. Les respostes van ser diferents per cada espècie i la carpa va ser la que va mostrar més clarament els impactes.
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The aim of this thesis is to contribute to the use of freshwater fish as ecological indicators in the Mediterranean basin. In the first article we found that although most biological indices were correlated, fish reflected different ecological aspects due to their particular features. In the second article the stream flow regimes of six Mediterranean basins were studied. A decrease of streamflow and aquifer levels was detected, despite no observed decrease of rainfall precipitation. Of the thirty metrics tested to detect sites impacted by water abstraction, we detected four significant fish metrics. Furthermore, the role of biotic indices when the river is artificially dry is discussed. In the third article we found that species composition in the pelagic zone varied significantly during the drawdown with higher proportion of bleak (A. alburnus) during the days of worst water quality, confirming that bleak is more tolerant than roach (R. rutilus) to poor water quality. The weight-length relationship of roach and bleak also varied significantly during the drawdown with close relationship between water quality and fish condition. In the fourth article the condition and fecundity of freshwater fishes were assessed in a highly polluted reservoir (Flix reservoir). We have shown significant increases of DELT anomalies and ectoparasite prevalences and decreases in condition and fecundity of several freshwater fish at the impacted area. The responses to the pollutants were species-specific and common carp was the species that showed more markedly the effects.
7
Shaw, Benjamin John. „The ecotoxicology of engineered nanoparticles to freshwater fish“. Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/565.
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The use of nanoscale materials is growing exponentially, but there are also concerns about the environmental hazard to aquatic biota. Metal-containing engineered nanoparticles (NPs) are an important group of these new materials, and whilst there are undoubtedly a plethora of beneficial uses for these NPs, it is essential that an appropriate risk assessment is carried out in order to protect the environment and human health, with the consumption of contaminated fish a distinct possibility. The current study aimed to assess the bioavailability, uptake and toxicological effects of two metal-NPs (TiO2 NPs and Cu-NPs) to fish from both dietary and waterborne exposure routes and where appropriate compare them to their bulk counterpart. Whole body system effects were assessed along with the influences of the life stage of exposed fish and abiotic factors on toxicity. A technique to improve the quantification of Ti from TiO2 NPs in fish tissue was also developed. Effects from exposure to dietary TiO2 NPs manifested similarly to traditional dietary metal exposure, with no reduction in growth, but some sublethal affects. Exposure to waterborne Cu-NPs showed that rainbow trout were more acutely sensitive to CuSO4 than the NPs, but that despite limited uptake several body systems were affected (most notably ionoregulation). Larvae were more sensitive to CuSO4 than Cu-NPs, but no differences were seen with embryos, whilst larvae were more sensitive than embryos. Abiotic factors did have an effect on acute Cu-NP toxicity, though not always in a predictable manner, with some effects more pronounced than with CuSO4. Overall, it appears that metal-NPs are not as acutely toxic as their bulk counterparts, but sublethal effects, were routinely observed. As TiO2 NPs appear more toxic than its bulk counterpart, current legislation governing safe environmental limits may have to be adjusted, though the situation with Cu-NPs isn’t as clear and further investigation is required. However, the risk of human exposure via the consumption of NP contaminated fish fillets is extremely low.
8
Brydges, Nichola M. „Cognition in freshwater fish : effects of the environment“. Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2388.
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For animals that live in a reasonably variable environment the capacity for learning and memory allow them to adapt to the changes they experience. Ecological factors that vary between habitats can affect a range of learning behaviours. Less attention has been directed at how this variation may affect memory processes, or how different ecological variables might interact when shaping cognition and behaviour. Therefore one aim of this thesis was to investigate how different ecological variables shape memory abilities and to test whether those same variables affect other related behaviours such as learning. In order to test this, I selected natural populations of a temperate freshwater fish, the three-spined stickleback (Gasterosteus aculeatus) from pond and river habitats that were proposed to differ in predation pressure, and assayed their learning, memory and other behavioural traits. Pond and river populations differed in their memory and orientation behaviour. An interaction between pond/river habitat and predation pressure affected learning rate, and a similar interaction affected temperament behaviours. Two further studies were conducted to address how captive rearing environments and typical handling procedures affect behaviour in different species. Rearing environment affected memory, but not learning or temperament behaviours in three-spined sticklebacks. Handling caused stress responses in three-spined sticklebacks, Panamanian bishops (Brachyraphis episcopi) and Rainbow trout (Oncorhynchus mykiss), but handling with a water filled scoop compared to a traditional dip-net decreased these responses in three-spined sticklebacks and Panamanian bishops, and also affected behaviour in Panamanian bishops. The results presented in this thesis suggest that ecological variables play a substantial role in shaping learning, memory and other behavioural traits in fish, and highlight the utility of behavioural assays in answering welfare-based questions.
9
Hartikainen, Hanna-Leena. „Freshwater bryozoan abundence, eutrophication and salmonid fish disease“. Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493801.
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This research investigates the links between nutrient enrichment, bryozoan abundance and the development of myxozoan parasites in bryozoans. It was found that bryozoan abundances are elevated in nutrient-rich rivers, demonstrating the potential bio-indicator value of bryozoans and predicting increased bryozoan abundances with increased planktonic productivity when space is not limiting. A comprehensive set of laboratory microcosm studies showed also that experimental nutrient enrichment increased growth rates and statoblast production in Fredericella sultana, corroborating the results from field surveys.
10
Calta, M. „Early development and gill function in freshwater fish“. Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307766.
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11
Liang, Yan. „Reclamation of wastewater for polyculture of freshwater fish“. HKBU Institutional Repository, 1997. http://repository.hkbu.edu.hk/etd_ra/137.
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12
Sternberg, David. „Life-History Traits and the Functional Diversity of Australian Freshwater Fish“. Thesis, Griffith University, 2014. http://hdl.handle.net/10072/367236.
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Australian freshwaters are home to approximately 256 fish species from 36 families, many of which are endemic to the country and considered threatened, vulnerable or rare in the wild. In part this is due to a long history of continental isolation where increasing aridity and flow unpredictability have given rise to a fish fauna characterised by a unique association of life-history traits (i.e. characteristics of an organism that contribute to its fitness or performance, and which allow it to function in the environment) in order to cope with natural variation in environmental seasonality, stability and predictability. My thesis presents an assessment of life- history traits and the functional diversity (the range and value of organismal characteristics) of Australian freshwater fish at multiple spatial scales (i.e. continental, river basin, catchment and population scales), with an emphasis on phylogenetic relationships, environmental determinants and conservation biology.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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13
Wang, Xi-chang. „Comparisons of Quality of Kamaboko Gels Derived from Freshwater Fish and Marine Fish“. Kyoto University, 2001. http://hdl.handle.net/2433/150361.
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14
Zha, Yinghua. „Assembly of Gut Microbial Communities in Freshwater Fish and Their Roles in Fish Condition“. Doctoral thesis, Uppsala universitet, Limnologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-314235.
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Animal hosts provide associated microorganisms with suitable ecological niches in their intestines. Microbes help their hosts to digest food, protect against pathogens, and influence the host’s metabolisms. Compositional variation of gut microbial communities is common among hosts, and may affect the health status of hosts. Diet and genetic factors are well known to influence the assembly of gut microbial communities. This thesis focuses on disentangling the contributions of factors including host genetics (sex), diet, environment, and other ecological processes to the assembly of gut microbial communities in freshwater fish. The association between gut microbial communities and fish condition is also evaluated in this thesis. Applying metacommunity theory, we found environmental factors including fish habitat, fish species, their diet, dispersal factors including microbes from fish diet, and ecological drift contributed to the assembly of fish gut microbial communities. The proportion of their contribution varied between fish species, where ecological drift explained more in perch than in roach. Under natural conditions fish populations face the risk of predation, which can induce competition and impose predation stress within prey individuals. This can therefore lead to changes in their diet qualities and quantities. In this thesis, it was shown that fish diet in terms of qualities and quantities significantly influenced the overall gut microbial composition, and this influence was dependent on fish sex, a host genetic factor. Predation stress was also suggested to significantly decrease the species richness. Furthermore, when fish were experiencing a diet shift, we showed that different bacterial phyla from novel food had different colonization success in the intestine, and this colonization success was positively influenced by predation stress. Fish condition was suggested in this thesis to be affected by gut microbial composition, especially by the contributions of the bacterial phyla Tenericutes and Actinobacteria.
15
Taylor, Lisa N. McDonald D. G. „Physiological indicators of waterborne copper toxicity in freshwater fish /“. *McMaster only, 2002.
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16
Kirkwood, Richard Christopher. „Interactions between fish, Mysis, and zooplankton in Lough Neagh“. Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268119.
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17
Khan, Tariq. „Exotic fish impacts on lake community structure and function in Western Victoria, Australia“. Thesis, Federation University Australia, 2002. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/164899.
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The researcher investigated a number of closed catchment lakes in western Victoria that have been stocked with exotic fish. Exotic-native fish interactions were studied and the potential of the exotic species to affect the lake ecosystem structure was explored.Doctor of Philosophy
18
Knight, Amelia Cassidy Terhune Jeffery S. „General fish health assessment and age evaluation of impinged fish at steam generating power plants“. Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/FALL/Fisheries_and_Allied_Aquacultures/Thesis/Knight_Amelia_50.pdf.
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19
Feist, Stephen Wolfgang. „Inter-relationships of myxosporeans, including PKX with certain freshwater fish“. Thesis, University of Plymouth, 1993. http://hdl.handle.net/10026.1/2755.
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The prevalence and impact of proliferative kidney disease (PKD) and myxosporidiosis has been investigated in wild fish stocks in the UK, over 1,500 fish representing 17 species being examined. PKD was recorded in brown trout, grayling and pike, the causative agent, the PKX cell, being identified with the aid of light and electron microscopy. A further 27 myxosporean species were also noted, with Myxobolus cotti (syn. M. jiroveci), in the brain of bullheads Cottus gobio being recorded for the first time. Studies on the structure and development of Myxidium lieberkuehni in pike revealed several previously undescribed features. Comparative morphological studies were undertaken to assess affinities of PKX with known myxosporean species. Results indicated similarities with early presporogonic stages of several myxosporean species, especially those belonging to the genus Sphaerospora. The apparent rarity of spore formation associated with PKX infections in the hosts examined focussed attention on species of Sphaerospora as possible sources of infection to salmonids. Studies concentrated on the possible involvement of the 3-spined stickleback, Gasterosteus aculeatus and its renal parasite, Sphaerospora elegans, in PKD transmission. A re-description of this parasite (recently elevated to "type species" for the genus), was prepared. Laboratory experiments using rainbow trout PKX cells successfully transmitted the infection to rainbow trout, brown trout, brook trout and grayling; however sticklebacks challenged with PKX cells did not appear to become infected. Rainbow trout challenged with S. elegans spores and presporogonic stages showed no evidence of sphaerosporosis or PKD. Experiments designed to investigate the possible role of tubificid worms in PKD transmission provided inconclusive results. Field studies provided data on the pathogenesis of PKD in grayling and showed this species to be highly susceptible to the disease.
20
Langford, Briana. „Analysis of the Fish Community on Tidal-Freshwater Constructed Reefs“. VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2852.
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Constructed reefs are used successfully in marine systems to enhance spawning habitat; this study examines the effectiveness of constructed reefs in a tidal-freshwater river. Fish abundance, species diversity and richness, residency, water column position, reproductive guilds, and feeding guilds were analyzed on two constructed reefs in the tidal-freshwater James River and compared to silted regions representing the primary substrate in the river. Reefs were sampled using hydroacoustics, electroshocking, gillnetting, trawling, and egg mats. The constructed reefs had a greater proportion of fish that broadcast spawn over hard substrate and a trend of more overall individual, residential, and demersal fish. The results suggest that the reefs may be attracting a different fish community than their respective comparison sites, though additional research on the effectiveness of constructed reefs in tidal-freshwater rivers is recommended.
21
Sheath, Danny. „Ecological consequences of indigenous and non-indigenous freshwater fish parasites“. Thesis, Bournemouth University, 2016. http://eprints.bournemouth.ac.uk/25014/.
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Parasites can have considerable consequences for their freshwater fish hosts, irrespective of whether they are intermediate or final hosts. The ecological consequences of infection arise from processes including parasite manipulation, where the parasite manipulates the host to increase their chance of transmission to the next host in the lifecycle, and parasite-mediated competition, where a consequence of infection is an alteration in the symmetry of competition between hosts and their uninfected conspecifics, or with other species. Whilst there is a great deal of existing knowledge on some of these consequences, there also remain some considerable knowledge gaps. This research covered the role of parasite exposure and water temperature on infection consequences, the foraging responses of fishes to intermediate hosts of the fish parasite Pomphorhynchus laevis that has an indigenous and non-indigenous range in Great Britain, the ecological consequences of this parasite for some freshwater fishes across these ranges, the issue of ‘enemy release’ and ‘parasite acquisition’ in introduced freshwater fishes, and the ecological consequences of infection by some native parasites for native freshwater fish. When the freshwater fish chub (Squalius cephalus) was exposed to different levels of intermediate hosts (Gammarus pulex) of P. laevis under two water temperature treatments, ambient and warmed, it revealed this interaction had considerable consequences for both parasite prevalence and the infection parameters. Whilst parasite prevalence was substantially higher at the elevated temperature, where infections did develop at lower temperatures, they were associated with fewer but larger parasites resulting in significantly higher parasite burdens, indicating complex consequences for host-parasite relationships under conditions of warming. Studies into parasite manipulation have frequently used the P. laevis: G. pulex parasite-intermediate host system for investigating how infections can result in behavioural modifications to the host that then results in their elevated risk of being predated by a fish. Here, comparative behavioural functional response experiments were used to test differences in the consumption rates of three fishes exposed to either uninfected or infected G. pulex, testing the hypothesis that the consumption rate of infected G. pulex would be significantly higher. The Type II functional response curves indicated that the results of the experiments were contrary to this hypothesis, with subsequent behavioural and foraging experiments also supporting these results. These counter-intuitive outcomes were also contrary to most other studies that suggested a parasite would manipulate its intermediate host in a way that promotes its transmission to a final host and facilitating the continuation of its life cycle. The reasons for these outputs were discussed as likely to relate to different selection pressures in this host-parasite system, given this is a generalist parasite with a wide range of potential fish final hosts. This was revealed by studies on this parasite from four fish species from five rivers that demonstrated high parasite prevalence in all species studied and suggested that small-bodied fishes, such as bullhead Cottus gobio, might play important roles in the P. laevis lifecycle. These prevalences, and the pathological consequences of the P. laevis infections, were also consistent across their indigenous and non-indigenous range, suggesting parasite origin had minimal consequences on their virulence and on the susceptibility of hosts to infection. That parasite origin often has minimal ecological consequences for their ecological impacts was reinforced by work on the ‘enemy release hypothesis’ in non-native fish in England and Wales. This revealed very few non-native parasites had been introduced with their non-native fish hosts. Those that had been introduced tended to be specialist parasites with direct lifecycles that had little opportunity to be transmitted to native fishes. Instead, the acquisition of native parasites by the non-native fishes was frequently observed, leading to potential concerns these fish would act as reservoir hosts and spill-back the parasites to the native fishes. Given the low probability of parasite introduction, the ecological consequences of three native parasites with complex lifecycles were then tested on three native fishes, and revealed consistent patterns of trophic niche divergence between infected and uninfected population sub-groups. Whilst the actual mechanism underpinning this, such as parasite-mediated competition, could not be tested, these results did reveal that the consequences of infection can be far-reaching for hosts and can be measured through a variety of methodologies. In summary, the research provided some comprehensive insights into many aspects of the pathological and ecological consequences of infection for some freshwater fishes from native/ non-native and indigenous/ non-indigenous parasites. In doing so, it has raised a series of new questions and hypotheses for further investigation, with the host-parasite systems used here capable of answering these.
22
French, Kenneth J. „Mercury evolution in freshwater fish from reservoirs in Newfoundland, Canada“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25841.pdf.
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23
Heath, Daniel D. „An experimental and theoretical investigation of stunting in freshwater fish /“. Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65985.
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Monopoli, Matthew Stephen. „Acid water tolerance in a New Zealand native freshwater fish“. Thesis, University of Canterbury. Zoology, 1996. http://hdl.handle.net/10092/6974.
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Physiological experiments were conducted to measure the effects of low pH water upon Na⁺ fluxes and swimming performance in east coast neutral water banded kokopu, and west coast banded kokopu living in naturally acid water. This allowed comparisons to be made regarding the relative acid tolerance between the two population stocks. A morphological study of the gills using scanning electron microscopy and transmission electron microscopy was carried out on a limited number of fish to compare gill structures of east coast acid and non acid exposed fish with west coast fish. East coast kokopu from neutral water showed a reduced sodium influx on the first day of exposure to pH4 water. This was accompanied by a reduction in passive loss or efflux. After 4 days at pH4 influx recovered allowing the fish to approach sodium balance. West coast fish showed no significant change in influx upon introduction to pH7 water and maintained influx values in pH4 water near those measured for control fish.
For east coast fish, swimming performance was significantly impaired on the 2nd swimming trial when pH was lowered from 7 to 4. On the third swim with the pH returned to 7, Ucrit was similar to the initial value. West coast banded kokopu showed a significant increase in performance between trial one and three and were unaffected by pH7 water, matching performances measured in control fish.
Gills from east coast acid exposed fish resembled west coast fish in that the trailing edges of the lamellae were swollen due to the large numbers of chloride cells which were present to a point approximately half way up the lamellar edge. Microridges were present on the apical surfaces of the chloride cells of east coast control fish which contrasted with the microvilli structures observed in west coast and acid exposed east coast fish. The microvilli structures present on the chloride cells of west coast and east coast acid exposed banded kokopu appeared to assist in the anchorage of mucus to the apical surface of the cell.
25
Longshaw, Matthew. „Studies on myxozoan parasites of freshwater fish and invertebrate hosts“. Thesis, University of Plymouth, 2004. http://hdl.handle.net/10026.1/2566.
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A study of myxozoan parasites has been investigated in hosts from freshwater environments in the UK. Over 17,000 oligochaetes, almost 5,000 juvenile cyprinids representing 7 species and over 60 invertebrate species have been examined for the presence of myxozoan parasites. In addition, studies on the lifecycle of Tetracapsuloides bryosalmonae (the causative agent of salmonid proliferative kidney disease, PKD) and of selected cyprinid myxozoans were conducted. A total of 21 actinospore types in seven collective groups were isolated and described from oligochaetes collected from seven different river systems in England and Wales. Twelve of the actinospores isolated appear to be new to science. Differences were noted in types of actinospores released at different sites and between seasons. Most actinospores were released from oligochaetes in spring and summer with prevalence of release ranging from 0.11% up to 5.83%. The most common actinospores were members of the collective group Echinactinomyxon with seven types identified, followed by the collective group Triactinomyxon, of which 6 types were identified. Five actinospores types were each encountered only once during the study. In juvenile cyprinid fish, 14 identifiable species of myxozoans in the genera Myxidium, Myxobolus and Sphaerospora plus three developmental stages were detected by histological examination. The most common myxozoans in cyprinids were Myxobolus pseudodispar and Myxobolus pfeifferi. Roach contained the most number of myxozoan species. Only seven myxozoan species were found in chub, but pathological responses and intensity of infections, particularly with M. pseudodispar, M. pfeifferi and Myxobolus buckei were greater when compared to other cyprinids examined. Juvenile cyprinids only appear to mount a pathological response to myxozoans once sporogony is initiated and some of those responses were considered severe enough to be detrimental to host survival. Mathematical models were produced using parasite data and incorporating a variety of data, including fish length, year class strength and environmental data to attempt to demonstrate a population level effect of disease. Many of the models developed clearly show that parasitism by Myxobolus spp. and Bucephalus polymorphus in juvenile fish is strongly correlated with population success in selected UK rivers. Laboratory experiments to transmit Myxobolus spp., Myxidium spp. and Sphaerospora spp. from selected cyprinid hosts to oligochaetes were unsuccessful. The most likely explanation is that the genetic strain of Tubifex tubifex used in the trials was not susceptible to infections by the myxospores selected. Specific DNA primers for Tetracapsuloides bryosalmonae were used on samples of over 60 invertebrate species collected from sites enzootic for PKD and on all 21 actinospore types isolated during the current study. All PCR reactions were negative for the presence of T. bryosalmonae DNA. Naive rainbow trout exposed to T. bryosalmonae spores from naturally infected bryozoans by bath challenge for 10 minutes developed PKD. Intraperitoneal injection of spores failed to induce the disease. The favoured route of entry by the parasite appears to be through mucous cells in the skin epithelium.
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Harrison, A. J. „Ecology and control of the freshwater fish louse (Argulus foliaceus)“. Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431598.
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Carrier, Roxie. „Temperature Tolerance of Freshwater Fish Exposed to Water-Borne Cadmium“. Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc504077/.
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Lethal toxicity values (96 h LC50; mg Cd/L) for the test species were similar: Lepomis cyanellus, 11.52; Notropis lutrensis, 6.62; Pimephales promelus, 3.58. However the effects of cadmium concentration and exposure time on temperature tolerance varied between species. Neither cadmium concentration nor exposure time had a significant effect on the CTM of green sunfish. Both cadmium concentration and exposure time had a significant effect on the CTMs of red shiners and fathead minnows. By day 10 mean CTMs were 2.3 t- 4.5 C (red shiners) and 4.2 to 5.7 C (fathead minnows) lower than control CTM. These results suggest a potential problem in cadmium contaminated systems for high environmental temperatures to stress or kill fish.
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Abban, Edward Kofi. „Taxonomy and biochemical genetics of some African freshwater fish species“. Thesis, Swansea University, 1988. https://cronfa.swan.ac.uk/Record/cronfa43062.
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CIUFFA, DANIELE. „Nutrients and fish effects on plankton community in freshwater mesocosms“. Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/962.
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Eutrophication affects many lakes in the world. Two important mechanisms to solve this problem are nutrient and fish control.
The main aim of the present work was to study nutrient and fish effects on plankton community in freshwater shallow lakes. Two mesocosm experiments were performed, one in spring and the other in winter to test differences in response of planktonic organisms to nutrient and fish addition in different seasons. The results would be of extremely importance for the management of these ecosystems.
Mesocosms were polyethylene bags filled with lake water and placed into the lake. Three different nutrient additions and three different fish densities were considered. All the possible combinations between these two factors were tested. Each mesocosm had a replicate, for a total of eighteen mesocosms in both seasons. Lake water was also sampled to test any differences between mesocosms and the natural ecosystem. Both experiments lasted six weeks. In the first week mesocosms were filled with lake water and nutrient and fishes were added. Each week, after sampling nutrients (nitrate and orthophosphate) were added. Fish used was Gambusia holbrooki mainly because its largely recognized planktivory. After the last week, benthic macroinvertebrates were sampled and stomach contents of fishes were analyses.
On the basis of the many studies demonstrating the significance to take into account functional groups of zooplankton, instead of consider total zooplankton density, in the present work four groups (rotifers, cladocerans, copepods and nauplii) were considered with regards to the zooplankton community.
Nutrients addition was associated to increase in phytoplankton biomass both in spring and winter although this increase was higher during spring. Nutrients did not affect zooplankton density neither in spring nor in winter. High fish density was associated to increase in phytoplankton biomass in both seasons. On zooplankton community, fish had a composite effect. They did not increase total zooplankton density neither in spring nor in winter. Fish changed zooplankton community. In spring, with increasing fish density rotifers increased while cladocerans and copepods decreased. In winter, zooplankton community was composed mainly by rotifers. Fish did not affect rotifers, but decreased cladocerans, copepods and nauplii. In spring, fishes could prey also on benthic macroinvertebrates. During winter, planktivory by fish was more intense due to the lack of benthic macroinvertebrates. Results show different response of plankton community between seasons. Results show the importance of considering as many variables as possible.
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McGlashan, Dugald James, und piscador@hotmail com. „Consequences of Dispersal, Stream Structure and Earth History on Patterns of Allozyme and Mitochondrial DNA Variation of Three Species of Australian Freshwater Fish“. Griffith University. Australian School of Environmental Studies, 2000. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030226.152217.
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Freshwater systems offer important opportunities to investigate the consequences of intrinsic biological and extrinsic environmental factors on the distribution of genetic variation, and hence population genetic structure. Drainages serve to isolate populations and so preserve historical imprints of population processes. Nevertheless, dispersal between and within drainages is important if the biology of the species confers a good dispersal capability. Knowledge of the population genetic structure or phylogeographic patterns of Australia's freshwater fish fauna is generally depauperate, and the present study aimed to increase this knowledge by investigating patterns of genetic diversity in three Australian species of freshwater fish. I was interested in the relative importance of dispersal capability, the hierarchical nature of stream structure and the consequences of earth history events on patterns of genetic diversity among populations. I examined three species from three families of Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), Craterocephalus stercusmuscarum (Atherinidae) and Hypseleotris compressa (Gobiidae). These species are abundant, have wide overlapping distributions and qualitatively different dispersal capabilities. I was interested in attempting to unravel how the biological, environmental and historical factors had served to influence the patterns and extent of genetic diversity within each species, thereby inferring some of the important evolutionary processes which have affected Australia's freshwater fauna. I used allozyme and 500-650bp sequences from the ATPase6 mitochondrial DNA (mtDNA) gene to quantify the patterns of genetic variation at several hierarchical levels: within populations, among populations within drainages and among drainages. I collected fish at several spatial scales, from species wide to multiple samples within drainages; samples were collected from the Northern Territory, Queensland and New South Wales. The species with the highest potential for dispersal, H. compressa, exhibited the lowest levels of genetic differentiation as measured at several allozyme loci (H. compressa: FST=0.014; P. signifer FST=0.58; C. stercusmuscarum FST=0.74). Populations of H. compressa also had low levels of mtDNA differentiation, with many recently derived haplotypes which were widespread along the coast of Queensland. This suggested either considerable gene flow occurs or recent demographic change in the populations sampled. As there was no relationship between geographic distance and genetic differentiation, the populations appeared to be out of genetic drift - gene flow equilibrium, assuming the two-dimensional stepping stone model of gene flow. Estimating contemporary gene flow was thus difficult. It was apparent that there has been a recent population expansion and / or contraction of H. compressa populations. It was concluded that there has been considerably more connectivity among populations of H. compressa in the recent past than either of the other study species. Populations of P. signifer showed considerable genetic subdivision at different hierarchical levels throughout the sampled range, indicating gene flow was restricted, especially between separate drainages. Two widely divergent regional groups which had high ATPase6 sequence divergence and approximately concordant patterns at allozyme loci were identified. Interestingly, the groups mirrored previous taxonomic designations. There was also significant subdivision among drainages within regional groups. For example, the adjacent Mulgrave-Russell and Johnstone drainages had individuals with haplotypes that were reciprocally monophyletic and had large allozyme frequency differences. This allowed me to examine the patterns of genetic differentiation among populations within drainages of two essentially independent, but geographically close systems. There was as much allozyme differentiation among populations within subcatchments as there was between subcatchments within drainages, and significant isolation by distance among all populations sampled within a drainage. This suggested that the estuarine confluence between subcatchments was not a barrier to P. signifer, but that distance was an important component in the determination of the distribution of genetic diversity within drainages in P. signifer. There were three main areas of investigation for C. stercusmuscarum: comparing upland and lowland streams of the drainages in north Queensland, investigating the consequences of eustasy on coastal margin populations and examining the intriguing distribution of the two putative sub species, C. s. stercusmuscarum and C. s. fulvus in south east Queensland. First, as populations in upland areas of east coast flowing rivers are above large discontinuities in the river profile, their occurrence is presumably the result of gene flow to and / or from lowland areas, or the result of invasions via the diversion of western flowing rivers. Concordant patterns at both genetic markers revealed that the latter possibility was the most likely, with fixed allozyme differences between upland and lowland populations, and large mtDNA sequence divergence. Indeed, it appeared that there may have been two independent invasions into the upland areas of rivers in North Queensland. Second, lowland east coast populations also had large, although not as pronounced, levels of population subdivision. Lack of isolation by distance, but with a concomitant high level of genetic differentiation among many comparisons, was consistent with a scenario of many small, isolated subpopulations over the range. Interestingly, widespread populations in central Queensland coastal populations (drainages which receive the lowest rainfall) were relatively genetically similar. This was consistent with the widest part of the continental shelf which at periods of lower sea level apparently formed a large interconnected drainage, illustrating the effect of eustatic changes on populations inhabiting a continental margin. Third, putative C. s. fulvus in lowland coastal Queensland drainages were genetically more similar to a population of C. s. fulvus collected from a tributary of the Murray-Darling (western flowing) than they were to adjacent putative C. s. stercusmuscarum. This implied that populations in south east Queensland, north to approximately the Burnett River, appeared to be derived from western flowing streams, and not via dispersal from other lowland east coast populations. Determining the relative importance of intrinsic and extrinsic factors to the development of population genetic structure is a difficult task. The present study demonstrated that the species with the highest dispersal potential had the lowest levels of genetic differentiation, waterfalls can limit gene flow, eustasy acts to join and separate populations leading to complex genetic patterns and that drainage rearrangements are important in determining the distribution of genetic diversity of populations now inhabiting isolated drainages. A difficulty with generalising about population genetic structure in obligate freshwater animals is the unique history of not only each drainage, but also the streams within that drainage and the idiosyncratic biological dynamics of the populations inhabiting those drainages.
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Duarte, Gonçalo Filipe Fernandes. „Ghost of diadromous fish past: streamlining research on diadromous fish species using historical data at european scale“. Doctoral thesis, ISA/UL, 2019. http://hdl.handle.net/10400.5/18329.
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Doutoramento em Restauro e Gestão Fluviais - Instituto Superior de Agronomia / Faculdade de Arquitetura / Instituto Superior TécnicoThe decline of diadromous fish species has been occurring at least since the beginning of the 20th century. In this thesis, multiple European databases on the historical distribution of diadromous fish were consulted and, acknowledging the lack of data for Portugal, the first database of Portuguese historical data for freshwater fish was created. The existence of multiple databases with distinct geographical coverage and data at different spatial scales lead to the development of an historical data framework able to deal with the limitations of historical data. Its output is a reliable and geographically broad dataset of diadromous species occurrence at the beginning of the 20th century at three spatial scales: basin, sub-basin and segment. Also, a software was developed to facilitate the acquisition of environmental and riverscape variables that can be linked with the data at the three scales. Longitudinal connectivity impairment, climate change and land use alterations are some of the most significant threats to diadromous fish species. The influence of these threats was studied performing a spatial and temporal analysis of the longitudinal connectivity impairment by large dams and, modelling the distribution of diadromous fish at the beginning of the 20th century using climate and land use variables. The longitudinal connectivity impairment of the European freshwater networks became widespread in the second half of the 20th century, and is currently more impactful for populations from basins in southern Europe. The distribution of diadromous fish species is mainly affected by climate, though the effects of land use close to river mouths may be relevant since these are critical passage and entry points for the remaining network. The framework and the software developed were key to achieve the scientific knowledge presented, and more importantly, these can be established as the structural basis for future research on diadromous fish species
N/A
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Branco, Paulo José de Lemos. „Improving connectivity for river fish“. Doctoral thesis, ISA, 2013. http://hdl.handle.net/10400.5/6447.
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Goss, Gregory Gerard. „Interrelationships between gill morphology and acid-base regulation in freshwater fish“. Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6794.
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This thesis examines the branchial mechanisms utilized by freshwater fish to regulate internal acid-base status and presents a model to explain the underlying basis of the compensatory processes. Rainbow trout, Oncorhynchus mykiss, brown bullhead, Ictalurus nebulosus, and American eels, Anguilla rostrata, were examined under a variety of experimental treatments which induced both respiratory (hyperoxia, hypercapnia) and metabolic (post-hyperoxia, post-hypercapnia, HCl infusion, NaHCO$\sb3$ infusion) acid-base disturbances. Acid-base-regulation was achieved by appropriate adjustments of Na$\sp+$ and Cl$\sp-$ net fluxes across the gills which, in turn, were accomplished by variable contributions of three different branchial mechanisms; (i) morphological adjustments to the gill epithelium, (ii) changes in internal (H$\sp+,$ HCO$\sb3\sp-)$ and external (Na$\sp+,$ HCO$\sb3\sp-)$ substrate availability, and (iii) differential changes in Na$\sp+$ versus Cl$\sp-$ net fluxes through regulation of Cl$\sp-$ efflux. This thesis determined the variable contribution of each of these mechanisms to overall compensation of acid-base disturbances. In brown bullhead and trout, respiratory acidosis caused a reduction in chloride cell (CC) surface area whereas alkalosis was associated with increases in CC surface area. Increases in the density of microvilli displayed on the external surface of the PVC coupled with ultrastructural modifications during hypercapnic acidosis were associated with increases in Na$\sp+$ uptake $\rm(J\sb{in}\sp{Na+}).$ In addition to the effect that alterations in CC surface area have on the rate of Cl$\sp-$/HCO$\sb3\sp-$ exchange $\rm(J\sb{in}\sp{Cl-}),$ it was demonstrated that changes in the concentration of the internal counter-ion (HCO$\sb3\sp-)$ may alter the rates of acid-base compensation. When (HCO$\sb3\sp-$) is elevated, $\rm J\sb{max}\sp{Cl-}$ is elevated thereby increasing the capacity to excrete HCO$\sb3\sp-$ via the Cl$\sp-$/HCO$\sb3\sp-$ exchanger over and above those determined by CC morphology. This is an important mechanism to increase the rate of acid-base compensation during metabolic alkalosis. (Abstract shortened by UMI.)
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Doehring, Anna Katharina. „Urbanisation influences on freshwater fish distribution and remediation of migratory barriers“. Thesis, University of Canterbury. Biological Sciences, 2009. http://hdl.handle.net/10092/2896.
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Ongoing urbanisation in lower stream reaches can adversely affect the ecology of river ecosystems by altering freshwater fish distributions. Diadromous fish species (those that migrate between the sea and freshwater) are particularly affected as unimpeded access to and from the sea is necessary for their life-cycle completion. To investigate the extent of the effects that urbanisation have on migratory freshwater fish species, I compared fish community composition between urbanimpacted and un-impacted waterways in the upper South Island, New Zealand. I also investigated whether culverts were barriers to inanga (Galaxias maculatus) juvenile migration, and experimentally tested different aspects of fish ramp designs for the remediation of juvenile inanga migration barriers. Analyses of fish community composition indicated significant differences between urban-impacted and un-impacted stream reaches. Fish species sensitive to poor habitat quality were generally absent from urban waterways. Inland penetration of fish species was reduced in urban-impacted than un-impacted streams, likely indicating culverts were upstream migration barriers. Laboratory experiments showed that climbing ability of inanga depended on fish size. Climbing also depended on the length and slope of the climb, but not the availability of resting pools. Experiments conducted at 13 natural culverts showed fish could not pass (0% passage) undercut (perched) culverts unless aided by an experimental ramp (44 % passage). To offer successful upstream passage for weak swimming species, culverts should ideally be box-shaped with widths and angles similar to the natural stream bed. Fish ramps should be designed to accommodate species with weak swimming abilities, considering trade-offs in ramp geometry. My results provide a framework for identifying and correcting barriers to diadromous fish passage, allowing managers and ecologists to maintain and enhance fish populations in urban environments.
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Perez-Camargo, Gerardo. „Effects of sublethal concentrations of pesticides on tropical freshwater fish quality“. Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294727.
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Bracewell, Philip John. „The effects of electric fishing on some freshwater cyprinid fish species“. Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327287.
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Shohet, Adam Joseph. „Mate choice and sexual selection in the guppy, Poecilia reticulata“. Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269307.
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Gardner, Christopher John. „The behaviour and ecology of adult common bream Abramis brama (L.) in a heavily modified lowland river“. Thesis, University of Lincoln, 2013. http://eprints.lincoln.ac.uk/14683/.
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Anthropogenic influences on riverine ecosystems have led to numerous impacts that have compromised fish communities. Large European lowland rivers have been amongst the most impacted aquatic environments globally. However, paradoxically, these environments have also been amongst the least studied, due the inherent difficulties of studying fish in large, turbid, dynamic environments. Common bream Abramis brama (L.) populations are amongst those impacted by reduced lateral and longitudinal connectivity that are a consequence of modifications to large lowland rivers in Europe. Thus common bream in the lower River Witham, Lincolnshire, UK, were selected as a case study to examine how fish utilize these river systems. A literature review was carried out to assess the influence of human intervention on riverine ecosystems and their impacts on fish communities. In addition the use of telemetry techniques for studying fish populations was reviewed. An ecological assessment of the lower River Witham was carried out using data available from The Environment Agency monitoring and hydrological systems and data specifically collected during this study. The history of this highly modified lowland river was reviewed to give perspective, timescale and context to the degree of modification that has been undertaken on the river and its consequences. Chemical and biological water quality indicators showed improvements in the last twenty years. Fisheries data identified three species that had become locally extirpated in the lower river since the 1800s. The river is now roach dominated, but common bream are still present, possibly due to available lateral spawning habitats that provide surrogates for, and are functionally similar to, the lentic floodplain waterbodies of natural riverine ecosystems. Hydroacoustic surveys show that fish communities are aggregated and favour the upstream half of the lower river where the channel is more heterogeneous. Recent changes in river character have made traditional fishery assessments by seine netting less effective. Data collected during fish tracking studies are most valuable when the tagged fish are behaving naturally, thus the effects of tag attachment should not impact on the behaviour or well being of the fish. Acoustic telemetry was used to investigate the impacts of tagging, surgical inter-peritoneal implantation, and translocation of common bream. Fish were recaptured following surgery and the incision site photographed to assess healing, which was clean in all cases. All recaptured fish appeared to be behaving normally as they were part of large shoals of fish. On five separate occasions fish were tagged when other previously tagged fish were present allowing their behaviour to be compared in terms of the distances moved and linear range; there were no significant differences between the two groups indicating the tagging procedure to have no detectable impact on the short-term behaviour of the fish at the resolution of the tracking undertaken. Three recaptured fish were translocated ~35 km downstream; these fish appeared to exhibit homing behaviour, returning to the capture site between 6-24 days. Their level of activity (in terms of distance moved) did not significantly differ from non-translocated fish, but their linear range was larger. The distribution and habitat use of adult common bream was assessed by tracking their longitudinal and lateral movements over forty-three months, producing a dataset of over 3.1 million detections. A positive relationship between activity and temperature was revealed, with common bream moving greater cumulative distances during the warmer months and occupying a greater longitudinal proportion of the main channel. The occupancy of tributaries was related to temperature, with common bream entering shallow tributaries during rising temperatures in the spring, whilst a deeper, slow-flowing tributary was used more frequently during the cooler autumn/winter months. During the autumn, occupancy of this deeper tributary was positively related to flow rate, suggesting that common bream use this as a refuge from high main channel flow. The home range concept is at the centre of theoretical models to explain the spatio-temporal behaviour of a wide range of animals including fish. There are lots of different ways of expressing home ranges, including areas, but since rivers are principally linear systems, most range is reflected linearly. Home ranges were calculated for 100% and 90% of locations. Seasonal differences were identified with fish occupying larger home ranges during the spring and summer opposed to autumn and winter. Artificial water level manipulations, management actions for the control of flood risk, affected home range size with fish occupying smaller ranges at reduced winter levels than at increased summer levels. Analysis of when and how often individuals within a population interact with one another provides a method to study the social organisation of animals with the potential to reveal ecologically significant aspects that would otherwise have remained hidden. Network analysis and social network theory were used to examine the social interactions of the tracked fish. The extent of sociality appears to follow a normal distribution, such that there was no evidence of discrete classes of social/non-social fish. Fish were more social immediately after tagging and less social as time progressed, as such little evidence could be found to support the hypothesis that these groups of fish remained in each others’ company for extended periods. However, more active individuals were found to be more socially connected, but home-range size did not significantly affect sociality. The functions of these behaviours are discussed along with potential management and rehabilitation strategies for the lower River Witham and other heavily modified lowland rivers in order to meet good ecological potential/status under the Water Framework Directive (2000/60/EEC).
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Warnick, William A. „Sport fish consumption advisory for West Virginia“. Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2681.
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Ozburn, Nicholas R. „Influence of dams on stream fish biodiversity across a diverse Georgia landscape“. Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/OZBURN_NICHOLAS_54.pdf.
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Go, Jeffrey. „Megalocytiviruses of freshwater ornamental fish and pathogenicity in marine and euryhaline species“. Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14118.
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Megalocytiviruses affect a broad range of fish species and have caused widespread mortality in aquaculture throughout Asia. The first confirmed report involved mass mortality in red sea bream cultured off Shikoku Island, Japan in 1990. Ornamental fish exhibiting pathology consistent with Megalocytivirus infection have been reported from a range of countries, frequently in association with fish recently imported from south east Asia. Although the relationship between megalocytiviruses in ornamental fish and food fish remains unclear, a potential linkage between a Megalocytivirus from a disease outbreak in Murray cod, Maccullochella peelii, in Australia and those in ornamental fish imported from south east Asia had been demonstrated experimentally. However, no data existed on the strains of virus involved in the first reported cases of Megalocytivirus-like pathology in ornamental fish. Furthermore, the potential for spread from ornamental fish to food fish other than Murray cod was also unknown. This study aimed to characterise Megalocytivirus from archival ornamental fish tissues, and to determine the potential for spread of megalocytiviruses from freshwater ornamental fish to other species, including marine fish. In situ hybridisation (ISH) assays were developed to demonstrate megalocytiviral DNA in tissue sections. The presence of megalocytiviral DNA was confirmed in two archival ornamental fish from 1986 and 1988 which had Megalocytivirus-like pathology. Unlike all other reported cases of Megalocytivirus in ornamental fish, these cases did not involve the Infectious spleen and kidney necrosis (ISKNV)-like genotype. The sequence of the major capsid protein (MCP) and the adenosine triphosphatase (ATPase) genes from the viruses in the archival tissues had a high degree of identity to each other (96.7-100%) and to a turbot reddish body iridovirus (TRBIV)-like Megalocytivirus (96.6-99.9%), reported as a cause of mass mortality in barred knifejaw, Oplegnathus fasciatus, fingerlings in Taiwan. By contrast, MCP sequences of Megalocytivirus in ornamental fish samples from 2002-2010 had almost complete identity to each other (99.9-100%) and to ISKNV, and only 91.5-95.0% identity to the archival samples, providing further evidence that these megalocytiviruses were genetically distinct. Megalocytiviruses in ornamental fish cases during 1986-1993 were TRBIV-like whereas all cases from 1996 onwards were ISKNV-like. Evidence also indicated that a single ornamental fish could be concurrently infected with two different megalocytiviruses. The confirmation of Megalocytivirus infection in ornamental fish prior to 1990 resulted in a revision of the index case for confirmed Megalocytivirus in any fish species. The detection of a novel TRBIV-like strain of Megalocytivirus in ornamental fish raised the possibility that current polymerase chain reaction (PCR) assays may not detect this group of megalocytiviruses. Consequently, new conventional and real-time quantitative (q) PCR assays were developed to differentiate between megalocytiviruses from each of the three major Megalocytivirus genotypes. The discovery of a potential link between historical cases of Megalocytivirus infection and a recent disease outbreak in barred knifejaw, provided further impetus for investigation of the potential for spread of megalocytiviruses from freshwater ornamental fish to marine fish species. The susceptibility of Australian bass, Macquaria novemaculeata, an important euryhaline Australian native species, to a Megalocytivirus (DGIV-10) originating from a recently imported dwarf gourami, Trichogaster lalius, was tested. Australian bass were susceptible to lethal infection with this Megalocytivirus both by direct inoculation and by cohabitation, and transmitted Megalocytivirus to naïve Murray cod through cohabitation. Australian bass could therefore be used as a model to study vector-borne transmission of Megalocytivirus between freshwater and marine fish species. Silver sweep, Scorpis lineolata, an Australian native marine fish was shown to be highly susceptible to DGIV-10 both by direct inoculation and cohabitation, and is the first Australian marine fish with demonstrated susceptibility to a Megalocytivirus originating from ornamental fish. Transmission of DGIV-10 from freshwater Murray cod to euryhaline Australian bass and then to marine silver sweep was demonstrated using cohabitation. Transmission of DGIV-10 from marine silver sweep to euryhaline Australian bass and then to Murray cod was also demonstrated. In summary, megalocytiviruses originating from the freshwater ornamental fish trade were demonstrated to be a potential biosecurity risk not only to Australian native freshwater species, but also to euryhaline and marine species and therefore to marine aquaculture, and recommendations for further research are presented.
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Currie, Rebecca J. (Rebecca Jean). „Upper and Lower Temperature Tolerances of Three Freshwater Game-Fish Species Exposed to Cycling Temperatures“. Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc279105/.
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A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.
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Kneeland, Stephen C. „Identification of Fish Hosts for Wild Populations of Rare Freshwater Mussels (Lampsilis cariosa and Leptodea Ochracea) Using a Molecular DNA Key“. Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/KneelandSC2006.pdf.
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Anandan, Chantelle. „Morphological and genetic differentiation of the fish eye fluke Diplostomum spp. (Digenea, Diplostomatidae)“. Thesis, University of Aberdeen, 2004. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186183.
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Digenean eye-flukes of the genus Diplostomum (Family: Diplostomatidae) are common in the eyes of freshwater fishes. Diplostomum spp. infections can lead to severe detrimental deformities and even death to both farmed and wild fish species. Identification of Diplostomum spp. in the fish host (metacercaria) is challenging because species are morphologically indistinguishable. Since Diplostomum spp. are difficult to identify the literature is confounded by synonymy and as a result, the taxonomic status of the genus remains unclear. Thus, it is difficult to ascertain the pathological status, diversity and geographical distribution of this economically important group of parasites. The purpose of this study was to define operational taxonomic units (OTU) using morphometric and molecular data collected from Diplostomum spp. metacercaria in the U.K. Data was collected from ten fish species and four host locations: lens humor retina and brain. Four OTU were defined by host location using morphometric analysis. Hence the morphometric analysis proved metacercaria from the four host locations were different in size and shape. Four OTU were discriminated using PCR-RFLP and sequence analysis. However, with the exception of brain parasites, those in the fish eye (lens, humor and retina) could not be differentiated by host location. Therefore, although parasites in the three fish eye locations were different in size and shape, they were not genetically different. The OTU ITS1 sequence data was compared to published Diplostomum spp. sequences and the following genetic similarity was revealed: OTU1 showed 99.4% similarity to D. mergi; OTU2 99.7% similarity to D. baeri and OTU3 99.7% similarity to D. paracaudum/D. spathaceum. OTU4 in the fish brain has previously been described as D. phoxini. The molecular approach was subsequently used in a temporal study to assess Diplostomum spp. metacercaria infections over the course of a year in a rainbow trout farm.
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Ozaktas, Tugba. „Multiple Antibiotic Resistance Of Surface Mucus Dwelling Bacterial Populations In Freshwater Fish“. Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609113/index.pdf.
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Surface mucus of a freshwater fish, Alburnus alburnus (bleak), caught from Lake Mogan, situated in south of Ankara, was collected in different seasons. The total cultivable bacteria were enumerated by spread plate method on nine different media. Bacteria were isolated based on colony morphologies and pigmentation. A total of sixty bacterial isolates obtained. The mucus-dwelling bacteria were first tested for resistance against ampicillin and kanamycinthen streptomycin and chloramphenicol were added to the experimental set up. The resistance levels of isolates were determined in terms of four antibiotics by tube dilution method. About 90% of the isolates were resistant to chloramphenicol, about 84% to kanamycin, about 88% to streptomycin and about 98% to ampicillin. These high levels of antibiotic resistance are rather interesting from a standpoint that the lake has no record of antibiotics exposure of any sort. The plasmid isolations were carried out to determine if the multiple antibiotic resistance could be attributed to plasmids for starting assumption. But we found no direct relationship between the presence of plasmids and multiple antibiotic resistance. Our study indicated that multiple antibiotic resistance at high levels is among the current phenotypes of the fish mucus-dwelling bacterial populations in Lake Mogan.
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Hamidan, Nashat A. „Ecology and conservation of Garra ghorensis, an endangered freshwater fish in Jordan“. Thesis, Bournemouth University, 2016. http://eprints.bournemouth.ac.uk/25214/.
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The focal species of the research was the freshwater cyprinid fish Garra ghorensis. Endemic to the southern Dead Sea basin of the Middle East, it is ‘Red listed’ by the IUCN as ‘endangered’. It inhabits the small rivers of the basin (‘wadis’), existing within fish communities of very low species diversity. The aim of the research was to inform conservation strategies for the species through investigations into their phylogeny, current distribution, life history traits and feeding relationships. Analysis of the mitochondrial DNA of G. ghorensis with other fishes of the Garra genus tested two contrasting hypotheses on their biogeographic origin: whether they were descended from Garra tibancia in the Arabian Peninsula or from a common ancestor shared with Garra rufa, which would have indicated dispersal from the Mediterranean basin and Mesopotamia. The phylogenetic tree clearly indicated that G. ghorensis shared a common ancestor with G. rufa and thus was of Mediterranean origin. These phylogenetic analyses were then important for interpreting G. ghorensis biogeography in relation to their natural range and current distribution. Surveys completed in 2010 provided data on their spatial distribution; this distribution was at least partially explained by historical geological and water salinity changes of the proto-lakes of Lake Samra and Lisan. These surveys also revealed that during the 2000s, there had been little change in G. ghorensis distribution, with populations still present in wadis that were recorded in 2002. However, at the surveyed sites, some alterations to the physical habitats and hydrology of the wadis were apparent, such as construction of impoundments. To assess the life history traits and feeding relationships of G. ghorensis, three locally abundant populations were studied. These were an allopatric population, a population sympatric with the native cyprinid Capoeta damascina and a population sympatric with the invasive cichlid Oreochromis aureus. The allopatric and sympatric native populations were present in wadis with minimal habitat disturbance, whereas the sympatric invasive population was present in a wadi with substantial alteration, including some impoundments that deepened the main channel and reduced the flow. Analyses of ages, growth rates and reproductive traits revealed that life spans, growth rates and reproductive investment were greatest at this disturbed site, despite being relatively altered from the apparently preferred habitat of the species. These results suggested that providing the hydrological disturbance at sites where G. ghorensis is present still enables the completion of their life cycle then their populations can withstand some aspects of habitat disturbances from anthropogenic activities. The feeding relationships of G. ghorensis were then assessed in relation to the presence of C. damascina and O. aureus in two of the sites, and used a combination of stomach contents analyses and stable isotope analysis. Results from both methods revealed whilst there were some overlaps in the trophic niches of the fishes, diets were based mainly on detritus and algae. These items are rarely limiting in freshwaters and thus whilst resources were shared, it was unlikely to result in high levels of inter-specific competition. Thus, an important ecological feature of G. ghorensis populations is their plasticity in life history traits and their resource use that enables some adaptation to disturbed environments. This suggests that their conservation management does not necessarily have to return their habitats to pristine conditions, as their adaptive capacity should enable some adaptation to the new conditions and thus continued population sustainability. Consequently, providing that development schemes prevent the destruction of the key habitats required for the completion of the G. ghorensis lifecycle, then their populations could remain sustainable in the face of continued development in the region.
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Moran, Rebecca Jayne. „The impacts of climate change on freshwater fish, macroinvertebrates, and their interactions“. Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533960.
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Gaze, William Hugo. „Studies on the biosystematics of Trichodinid ciliates parasitic on British freshwater fish“. Thesis, University of Stirling, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296749.
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Godfrey, Paul C. „Recruitment Ecology of Freshwater Fish in Rivers of Australia's Wet Tropics Region“. Thesis, Griffith University, 2012. http://hdl.handle.net/10072/367117.
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Hydrologic variation has a profound influence on the life cycles of fishes in tropical rivers. Several studies highlighting the critical links between fish recruitment, river hydrology and other environmental factors exist globally. However, understanding of the influence of abiotic drivers on fish recruitment in Australia’s Wet Tropics rivers is limited. There is potential for humans to further alter the hydrologic regimes and the landscapes of these rivers and therefore, gathering knowledge about fish recruitment dynamics is needed to support the implementation of appropriate management strategies aimed at preserving the diversity within the Wet Tropics freshwater fish community. This thesis investigates relationships between key environmental factors – river hydrology, instream habitat structure and food availability – and fish recruitment among five coastal rivers in the Wet Tropics bioregion of north-eastern Australia, and describes how differences in key flow-regime attributes among the rivers may influence these relationshipsThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Elberizon, E. „Empirical and theoretical modelling of waste output and distribution from freshwater aquaculture cages“. Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/554.
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