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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Applications of microsatellite markers to genetic management of carps in aquaculture

Gheyas, Almas Ara January 2006 (has links)
Carp aquaculture in South Asia suffers severely from a lack of genetic management, which has eroded the genetic quality of both captive and wild populations. Use of molecular markers, especially microsatellites, has revolutionized genetic management of hatchery stocks through its ability to detect kinship between individuals and hence in controlling level of inbreeding and loss of genetic diversity. In the present PhD work, microsatellite markers were applied to breeding programmes for silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) to study different genetic management aspects and new markers were generated from rohu (Labeo rohita). A set of newly isolated microsatellite markers from silver carp were characterized and two pentaplex PCR reactions were optimized to enable rapid genotyping of large number of individuals at 10 microsatellite loci. The utility of these markers in parentage, sibship and relatedness analysis were assessed by applying them to groups of fish with known relationship. These markers were used for parentage analysis in a breeding programme designed to estimate heritability of harvest weight and length in silver carp. Full- and half-sib families were created in three sets of partly factorial mating and all the families from each set were reared in communal ponds from very early life stages. With ten microsatellites 96.3% of the offspring could be assigned to a single family. Heritability estimates were found to be 0.65 ± 0.13 for weight and 0.50 ± 0.13 for length. High estimates of h2 suggested that this population should respond rapidly to selection for increased harvest size. Microsatellite markers were also applied to monitor the early stages of a mass selection programme in common carp (Cyprinus carpio). The selection was initiated from a base population synthesized from six different stocks. The selected individuals were divided to create two separate lines. The aims of this study were to monitor whether the stocks were represented in the intended proportions in the F1 selected populations, to investigate the relative contribution of families and its impact on effective population size and to identify any loss of molecular genetic variation. Five highly polymorphic microsatellites were used for parentage analysis of the selected fish to track stock and family contribution. Overall, large perturbations were observed in the relative contributions of two major stocks. Family contribution was also highly variable, causing the Ne to drop to below half the census size. A loss of 6.9%-12.2% of microsatellite alleles was observed but loss of heterozygosity was not very prominent. The replicate lines showed significant differences in allelic distribution after the first generation of selection, but not in genotypic distribution. Finally, 52 microsatellite markers were isolated from a partial genomic library of rohu using a selective hybridization protocol. Characterization of these markers resulted in 36 polymorphic loci, which will be useful in future work on conservation and management of both wild and captive rohu populations.
32

Genetic evaluation of American shad Alosa sapidissima restoration success in James River, Virginia

Aunins, Aaron 03 November 2010 (has links)
The American shad Alosa sapidissima has experienced severe declines throughout its native range due to habitat degradation, fragmentation, and over-fishing. Hatchery supplementation is often used for stock restoration, but the effects of supplementation on population structure and genetic diversity are rarely assessed. This study employed molecular markers to evaluate how supplementation of the James River American shad population with Pamunkey River origin larvae since 1994 has impacted genetic diversity and population structure. Population genetic parameters of other major Chesapeake Bay tributaries (Susquehanna, Rappahannock, Potomac, and Nanticoke) also were characterized. Prior to stocking, the James and Pamunkey populations exhibited subtle genetic differentiation, which was absent among post-supplementation samples, presumably due to the stockings. A similar situation was observed among other shad populations of Chesapeake Bay tributaries which were subtly differentiated in the 1990s but lacked any credible among-population differentiation among contemporary samples. Genetic diversity of the James River shad population was high prior to stocking, and remained high throughout years of intensive supplementation, yet the current population decline suggests that the James River shad population still has not recovered. Despite harvest curtailment, elimination of the ocean intercept fishery, and widespread supplementation efforts, Chesapeake Bay tributary American shad populations are collectively at their lowest levels in recorded history. Therefore, success of other restoration goals such as creation of fish passage in James River was investigated in a concurrent radio telemetry study to assess passage at Bosher's Dam fishway. Ninety-four American shad were radio-tagged on the spawning grounds below Bosher's Dam. Approximately one-half of the tagged shad were detected at the escapement receiver within 24 hours after tagging, and the average residence times of remaining shad were approximately one week. No tagged shad were detected above Bosher's Dam. These results imply that restricted passage through Bosher's Dam fishway may be an important factor in the failure of James River American shad to recover. Therefore, improving passage at migratory barriers such as Bosher's Dam, in conjunction with a continued Bay-wide fishing moratorium, may be more beneficial to shad restoration efforts in James and other Chesapeake Bay tributaries than continued supplementation.
33

The Ecology of Fear: Oviposition and Colonization in Aquatic Systems

Pletcher, Leeanna 24 April 2008 (has links)
Amphibians and aquatic invertebrates have complex life histories that link aquatic and terrestrial food webs. It has been suggested that amphibian reproduction is an important source of carbon to some aquatic systems. This process of energy flow may be shaped by shifts in habitat selection in response to predators. We hypothesized that predators decrease colonization and oviposition of prey, reducing active inputs. Thus predation risk is expected to shift the relative amounts of active and passive subsidies. We manipulated the presence of fish predators in aquatic mesocosms. Results suggest hylid treefrog eggs and hydrophilid beetles were less abundant in predator treatments. This difference in oviposition and colonization translated into small reductions in calories and ash free dry mass of active inputs. However, passive allochthonous inputs were more than double active amounts and variable, therefore relative amounts of active and passive inputs did not differ across the levels of predation risk.
34

Migration and quality of landlocked Atlantic salmon smolt : Implications for conservation and management

Norrgård, Johnny R January 2014 (has links)
Atlantic salmon Salmo salar has a complex life cycle, including long migrations and habitat shifts for both juveniles and adults. As such, salmon populations are vulnerable to habitat degradation and fragmentation along their migratory routes. This makes management and conservation a complex task requiring knowledge of salmon ecology at different temporal and spatial scales. In this thesis I highlight the use of a holistic life-history based approach in the conservation and management of wild and hatchery-reared salmon in regulated rivers and lakes. Small populations of wild-reproducing landlocked salmon and trout Salmo trutta exist in the regulated River Klarälven, Sweden. Since the 1930s, transportation of adult spawners upstream of eight dams has given the fish access to spawning grounds. The number of returning wild spawners became critically low in the 1960s, but stocking of hatchery smolts resulted in an increase in spawners that continues today. My data show that wild smolt may suffer high mortality due to multiple dam passages. To ensure viable populations of wild populations, future management should include both up- and downstream solutions that ensure connectivity in the system. The recreational and commercial salmonid fishery are maintained by compensatory stockings, yielding annual catches of about 75 tons, and a river return rate of hatchery fish of about 1%. As a large portion of the stocked smolts does not survive downstream migration to the lake, there has been discussion about the quality of the stocked smolt and about stocking strategies. Based on my studies, producing hatchery smolts more closely resembling wild-born conspecifics should result in reduced loss rates. I suggest changes in the hatchery and stocking procedures to increase the survival of stocked smolts. The results of my research should be applicable to other regulated systems, particularly those with mixed stocks of wild and hatchery salmonid populations. / Atlantic salmon Salmo salar has a complex life cycle, including long migrations and habitat shifts for both juveniles and adults. As such, salmon populations are vulnerable to habitat degradation and fragmentation along their migratory routes, which make management and conservation a complex task requiring knowledge of salmon ecology at different temporal and spatial scales. In this thesis, I highlight the use of a holistic approach in the conservation and management of wild and hatchery-reared salmon in regulated rivers and lakes. Small populations of wild-reproducing landlocked salmon and trout Salmo trutta exist in the regulated River Klarälven, Sweden. Since 1930, transportation of adult spawners upstream of eight dams has been done to give the fish access to the spawning grounds. My data indicate that a large proportion of the wild smolts are lost due to multiple dam passages, and future management should include both up- and downstream solutions, ensuring connectivity in the system. The fishery in Klarälven and Lake Vänern is maintained by compensatory stockings, yielding catches of about 75 metric tons and a river return rate of stocked fish of about 1%. I suggest changes in the hatchery and stocking procedures to increase the survival of stocked smolts.
35

Genetic and Ecological Consequences of Fish Releases : With Focus on Supportive Breeding of Brown Trout <i>Salmo trutta</i> and Translocation of European Eel <i>Anguilla anguilla</i>

Dannewitz, Johan January 2003 (has links)
<p>Although the practice of releasing fish into the wild is common in the management and conservation of fish populations, the success of release programmes and the potential harmful genetic and ecological effects that may follow are rarely considered. This thesis focuses on genetic and ecological consequences of fish releases, exemplified by supportive breeding of brown trout (<i>Salmo trutta</i>) and translocation of European eel (<i>Anguilla anguilla</i>). Specific questions addressed include: What is the relative performance of hatchery produced fish released to support wild populations, and do released hatchery fish contribute to the natural productivity? What is the variation in reproductive success in the wild, and how does it affect the genetic consequences of a supportive breeding programme? Is there a spatial genetic structure in the European eel that must be considered in the management of this rapidly declining species?</p><p>Experiments conducted under natural and near-natural conditions in the River Dalälven, Sweden, suggest that hatchery produced trout can reproduce in the wild. In fact, when the pronounced variation between individual breeders was accounted for, there were no detectable differences between hatchery produced and wild born trout in reproductive success or offspring survival. These results were supported by molecular genetic data suggesting a pronounced gene flow from hatchery to wild trout in the river. Hatchery reared trout were, however, found to exhibit reduced survival rates immediately following release into the wild, an effect that was most likely due to phenotypic responses to the hatchery environment during ontogeny and a lack of experience of the wild.</p><p>In sharp contrast to recently published studies, the present genetic analyses of European eels sampled across the whole distribution range suggest no spatial genetic structure but a subtle temporal genetic heterogeneity within sampled locations. These results emphasise the need to consider temporal replication when assessing population structure of marine species.</p><p>The results obtained have general implications for the management and conservation of fish populations. First, supportive breeding of threatened salmonid populations might be successful, not only for boosting the census size and thereby reducing the short-term probability of extinction, but also for reducing the risks of inbreeding depression and loss of adaptive potential in future generations. However, the results also highlight the need to restore the natural productivity of a population under supportive breeding to avoid a potential reduction in fitness due to hatchery selection. Further, the lack of a detectable spatial genetic structure in the European eel suggests that the management strategy of translocating juvenile eels from locations were they are overabundant to other suitable freshwater habitats does not necessarily have to include genetic considerations with respect to the geographical origin of the translocated eels.</p>
36

Genetic and Ecological Consequences of Fish Releases : With Focus on Supportive Breeding of Brown Trout Salmo trutta and Translocation of European Eel Anguilla anguilla

Dannewitz, Johan January 2003 (has links)
Although the practice of releasing fish into the wild is common in the management and conservation of fish populations, the success of release programmes and the potential harmful genetic and ecological effects that may follow are rarely considered. This thesis focuses on genetic and ecological consequences of fish releases, exemplified by supportive breeding of brown trout (Salmo trutta) and translocation of European eel (Anguilla anguilla). Specific questions addressed include: What is the relative performance of hatchery produced fish released to support wild populations, and do released hatchery fish contribute to the natural productivity? What is the variation in reproductive success in the wild, and how does it affect the genetic consequences of a supportive breeding programme? Is there a spatial genetic structure in the European eel that must be considered in the management of this rapidly declining species? Experiments conducted under natural and near-natural conditions in the River Dalälven, Sweden, suggest that hatchery produced trout can reproduce in the wild. In fact, when the pronounced variation between individual breeders was accounted for, there were no detectable differences between hatchery produced and wild born trout in reproductive success or offspring survival. These results were supported by molecular genetic data suggesting a pronounced gene flow from hatchery to wild trout in the river. Hatchery reared trout were, however, found to exhibit reduced survival rates immediately following release into the wild, an effect that was most likely due to phenotypic responses to the hatchery environment during ontogeny and a lack of experience of the wild. In sharp contrast to recently published studies, the present genetic analyses of European eels sampled across the whole distribution range suggest no spatial genetic structure but a subtle temporal genetic heterogeneity within sampled locations. These results emphasise the need to consider temporal replication when assessing population structure of marine species. The results obtained have general implications for the management and conservation of fish populations. First, supportive breeding of threatened salmonid populations might be successful, not only for boosting the census size and thereby reducing the short-term probability of extinction, but also for reducing the risks of inbreeding depression and loss of adaptive potential in future generations. However, the results also highlight the need to restore the natural productivity of a population under supportive breeding to avoid a potential reduction in fitness due to hatchery selection. Further, the lack of a detectable spatial genetic structure in the European eel suggests that the management strategy of translocating juvenile eels from locations were they are overabundant to other suitable freshwater habitats does not necessarily have to include genetic considerations with respect to the geographical origin of the translocated eels.
37

Environment-induced Phenotypic Plasticity in the Teeth of Hatchery and Wild Largemouth Bass, <i>Micropterus floridanus</i>

Selvaraj, Tamilselvi 01 August 2010 (has links)
Successful stock enhancement of hatchery-reared fish depends heavily on the release of individuals able to demonstrate strong survival skills. Overall survival of fishes is a reflection of a successful blend of physiology, anatomy, and behavior. With fishes being highly phenotypically plastic, the potential exists for all aspects of hatcheryreared fish to vary significantly from their wild counterparts while having potentially adverse effects on their survival after release. Previous analyses have demonstrated significant differences between the feeding behavior of hatchery-reared and wild caught largemouth bass (Micropterus floridanus) in the laboratory, as well as differences in the development of the skull between these two groups. The aim of this study was to determine if oral and pharyngeal jaw dentition differed between hatchery and wild bass. Scanning electron micrographs of the oral and pharyngeal jaws from an overlapping size range of 30 hatchery-reared and 30 wild bass were compared for the number and characteristics of oral and pharyngeal teeth. Wild bass were found to have features which would presumably allow more efficient capture of prey. The results of the study suggested that wild bass exhibited greater number of teeth when compared to hatchery reared bass. They also exhibited oral and pharyngeal teeth which were greater in length, and pharyngeal teeth that were greater in width when compared to hatchery-reared bass. This deficiency in dentition could have a significant effect on prey-capture success when introduced into the wild. We suggest that exposure to wild prey during the grow-out phase of aquaculture could provide the necessary adaptive plasticity of hatchery-reared bass dentition
38

The extent of hatchery-origin fish among fall chinook salmon (Onchorhynchus tshawytscha) observed in South Puget Sound tributary streams

Kennedy, Kevin M. January 2008 (has links) (PDF)
Thesis (M.E.S.)--The Evergreen State College, 2008. / Title from title screen (viewed 2/25/2010). Includes bibliographical references (leaves 95-101).
39

Research and development of hatchery techniques to optimise juvenile production of the edible sea urchin, Paracentrotus lividus

Carboni, Stefano January 2013 (has links)
Research and development in aquaculture has supported the knowledge-based development of the sector over the last decades. In particular, species diversification is playing an important role to ensure sustainability of the industry and helping to reduce pressure on wild stocks of those aquatic species for which farming technology is still at the early stages. Due to the increasing pressures on more traditional carnivorous marine finfish species (aquafeed reliance on fishmeal and fish oil, environmental impact, market price) low trophic organisms are receiving more attention to provide sustainable alternatives and integrate production activities with the aim of reducing environmental impacts and to provide secondary high value crops. Integrated Multi-Trophic Aquaculture (IMTA) systems are therefore at the forefront of innovation in the industry. Several invertebrate species have been investigated and tested as integral part of IMTA (mussels, oysters, abalone and macroalgae) and echinoderms have also been considered as good candidates for the future development of this technology. In order to allow for a more widespread uptake of integrated aquaculture, several technical and biological challenges need to be overcome, including a reliable supply of juveniles. In recent years, this has prompted investigation on Echiniculture as a whole and on hatchery technologies in particular. This PhD investigated key constraints in edible sea urchin (Paracentrotus lividus) juvenile production with the aim to improve commercial sea urchin hatchery outputs. The research firstly focused on larval nutrition (Chapter 3 and 4) and specifically tested the hypothesis that larvae required higher dietary inputs of long chain fatty acids than those provided by Dunaliella tertiolecta, a microalgae species widely used in echinoderm larval rearing. Fatty acid composition of P. lividus eggs, investigated in Chapter 3, supported this hypothesis, which was further confirmed by the results obtained in Chapter 4 where microalgae (Cricosphaera elongata, Pleurochrisis carterae and Tetraselmis suecica) with a more balanced fatty acid profile, in particular richer in long chain fatty acids, were employed. This resulted in a significantly improved larval development and survival. Results also indicated that these alternative microalgae species could be successfully grown without modification of the microalgae production protocols in the hatchery where the experimentation had taken place. The third experimental chapter compared static and flow through systems which provides more stable water quality through constant water exchange and reduces larval handling and associated stress. Results indicated that larval survival was significantly improved by the flow-through system and the need for tank cleaning was reduced (three versus seven times per larval cycle when using flow-through and static rearing systems respectively). However, water quality, based on the parameters assessed (NH4, PO4-3, NO2 and NO3), did not show any significant differences between systems. Reduced handling could have therefore played the most important role in promoting larval survival. Both these trials resulted in a significant 5 to 20 % increased survival. A follow-up study, combining flow-through with more suitable microalgae, should be carried out and could result in even further enhanced survival. Then, chapters 6 and 7 focused on broodstock nutrition and subsequent improvement of gamete quantity and quality. These two trials aimed to explore and describe the biological effects that some important nutrients, such as proteins, lipids, fatty acids and carotenoids, have on urchins’ somatic and gonadal growth, gonad biochemical composition during gametogenesis, fecundity and maternal provisioning to developing embryos. Results from the experiment described in Chapter 6 indicated that higher protein content can improve somatic growth in P. lividus adults and that more expensive, protein-, lipid- and energy-rich diets do not significantly enhance fecundity or offspring performance. Results, moreover, highlighted the need for a specifically formulated broodstock diet and gave some insights into what its composition should be, especially in relation to carotenoids. In Chapter 7, fatty acid profiles of P. lividus gonads throughout gametogenesis were studied for the first time. It was observed that, among Long Chain Polyunsaturated Fatty Acids (LC-PUFAs), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) are primarily accumulated during gametogenesis, whilst Arachidonic acid (ARA) appears to be independent of dietary input. In addition, it was clearly shown that ARA is the only LC-PUFA accumulated in the eggs along with Non Methylene Interrupted Fatty Acids (NMI FAs). As well as looking at the biological effects of different diets on fatty acid profiles of gonadal and larval tissues, the work also expanded on a more fundamental level to explore the metabolic pathway through which precursors could be used by sea urchins for the endogenous production of long chain fatty acids (Chapter 8). Three Expressed Sequence Tags (ESTs) for putative fatty acyl desaturases, one of which was closely related to Octopus vulgaris ∆5-like fatty acyl desaturase, were identified. The newly cloned putative desaturase of P. lividus possessed all typical features of other fatty acyl desaturases. However, because of time constraints, functional characterisation, originally planned, of the new protein could not be performed and further research effort is needed to investigate this important aspect of sea urchin physiology. Overall, the aim of this research project has been achieved as it provided a set of exploitable results and protocols to improve hatchery practices for the production of P. lividus juvenile. However, more research is required to investigate some of the underlying mechanisms behind the observed biological effects such as delay in larval development when T. suecica was used as larval feed, increased broodstock fecundity, improved larval survival in the flow-through system and higher gonadal concentration of some fatty acids (mainly DHA) than provided in the feed.
40

Effekt av berikad vs standard odlingsmiljö på beteende och tillväxt hos lax / The effect of enriched vs standard hatchery conditions on Atlantic salmon behavior and growth

Björndotter, Erica January 2015 (has links)
ABSTRACT The farming of salmon in hatcheries has been used to compensate for the decline of many wild populations due to human activity. Recent evidence has indicated that standard farmed salmon have a  higher mortality than wild fish, leading to the question of whether hatchery conditions can be altered to improve survival of stocked salmon. The purpose of this study was to compare the behavior and growth of hatchery-raised Atlantic salmon (Salmo salar) raised under standard conditions vs varied (enriched) hatchery conditions. The hypothesis was that fish from enriched rearing would grow faster, presumably due to more efficient foraging, resulting in less total movement, In addition, I predicted that salmon from enriched conditions would  have a higher biomass of food in their stomachs than fish reared under standard conditions. Salmon from the two different groups, enriched and standard, were held separate during their first 12 months of life. The following nine months the fish were raised together in semi-natural outdoor tanks. Behavior and growth of the fish were measured during this latter period. The results showed no support for my hypotheses. Biomass of food contents and summer and winter growth did not differ between treatments. I did find, however, that fish farmed in enriched environments were more active during the summer than fish raised under standard conditions. This suggests that early rearing conditions affect the behavior of the fish, but it is unclear if this effect has any bearing on survival of the fish when stocked in rivers. / SAMMANFATTNING Odling av laxar i anläggningar har använts för att kompensera för den minskning som sker i många vilda populationer på grund av mänsklig aktivitet  Nutida bevis har indikerat att lax odlad inom standardiserade förhållanden har högre dödlighet än vild fisk, vilket leder till frågeställningen om hurvida odlingsförhållanden kan utvecklas för att förbättra överlevnaden hos utsatt odlad lax. Syftet med denna studie var att jämföra beteende och tillväxt hos odlad Atlantlax (Salmo salar) inom standardiserade odlingsmetoder mot varierande förhållanden inom (berikad) odling. Hypotesen var att fisk från berikad odling skulle växa fortare, förmodlingen pågrund av ett mer effektivt födosök, medförande lägre total rörelse, dessutom, förutsåg jag att lax från berikad miljö skulle ha högre biomassa mat i magarna än fisk odlad inom standardiserade metod. Lax från de två olika grupperna, berikad och standard, var separerade under deras 12 första månader. De följande nio månader odlades fisken tillsammans i semi-naturliga utomhustankar. Beteende och tillväxt mättes under den senare perioden. Resultatet visade ingen signifikant skillnad till stöd för mina hypoteser. Biomassan av maginnehåll och sommar och vintertillväxt skiljde sig inte mellan behandlingarna. Däremot fann jag att fisk odlad i berikad miljö var mer aktiva under sommarperioden jämfört med fisk från standardiserad odling. Detta tyder på att tidiga odlingsmetoder påverkar fiskens beteende, men det är oklart om denna effekt har någon betydelse för fiskens överlevnad vid utsättning i älvar.

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