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Molecular genetic markers can be used to assess genetic diversity, assign parentage, quantify inbreeding, and demonstrate structuring of populations across a system. Striped Bass Morone saxatilis, and Walleye Sander vitreus, are widely sought gamefishes in the Commonwealth of Virginia. Striped Bass along the Atlantic Coast and within the Roanoke River drainage exhibit low genetic variation. Screening 12 microsatellite DNA markers across the range to define population genetic structure, I found that anadromous populations in the Southeast and the Chesapeake Bay were differentiated from landlocked populations in the Roanoke River basin, with an average FST of 0.066. Range-wide, Striped Bass are differentiated between the landlocked and anadromous populations, which need to be managed separately. Within stocked populations in the Roanoke River basin, there have been impacts stemming from small numbers of broodstock propagated, and inter-individual relatedness is ~20% within stocked reservoirs. Walleye across the eastern native range were screened to better understand evolutionary history and to identify native marker alleles for the upper New River population. Population genetic variation at eight microsatellite loci showed differentiated stocks in Alabama, Mississippi River, Eastern Highlands (Tennessee, New, and Ohio Rivers), and the Great Lakes drainages. All estimates of effective numbers of breeding individuals were under 25, and all populations within all watersheds had ~15-20% inter-individual relatedness, likely effects of both natural demographic processes and stocking. The extent of Eastern Highlands Walleye includes both the Ohio and Tennessee basins. Although I did not identify new marker alleles for native New River Walleye, I determined that marker-assisted selection has increased the frequencies of existing marker alleles for the native stock. Application of the results of this project will contribute to better fisheries management for both of these important species. / Master of Science / Population genetics have proven useful for defining the most appropriate units for conservational management across a variety of species. Molecular genetic markers can be used to assess genetic diversity, assign parentage, quantify inbreeding, and demonstrate structuring of populations across a system. Striped Bass Morone saxatilis and Walleye Sander vitreus are both widely sought gamefishes in the Commonwealth of Virginia. I applied population genetic approaches to recognize genetically distinct groups of populations and to recommend genetically cognizant management practices. Striped Bass across the Atlantic Coast and in the Roanoke River drainage exhibit low genetic variation. After screening variation at 12 DNA markers, I found that Striped Bass are differentiated between landlocked and migratory populations, which need to be managed separately. Within stocked populations in the Roanoke River basin, there have been impacts stemming from propagation of small numbers of broodstock, and propagation and stocking practices will need to be changed to reduce apparent inbreeding depression. Walleye populations across the eastern native range were screened to better understand evolutionary history and to seek new marker alleles for the native upper New River population. After screening genetic variation at eight DNA marker loci, I identified four evolutionarily distinct stocks of Walleye across eastern North America. Although I did not identify new marker alleles for native upper New River native Walleye, I showed that marker-assisted selection has increased the frequencies of existing marker alleles over the past twenty years. The results of this project can contribute to better fishery management strategies for both of these important gamefish species.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

There is concern regarding exposure of aquatic organisms to chemicals that interfere with the endocrine system. Disruption of the endocrine system can lead to impacts on sexual development, altered hormone levels, intersex, and ultimately reproductive failure. While effects of endocrine disrupting chemicals (EDCs) on standard laboratory species have been subject of intense study, to this day there is a large gap in knowledge and a high degree of uncertainty regarding the sensitivity of wild fish species to these compounds. One of the main concerns with current toxicity testing approaches is that they require the use of a large number of live animals, particularly when working with native species. Therefore, the aim of this study was to develop in vitro tissue explant assays that would enable the assessment of the sensitivity of different wild fish species native to North America to the exposure with EDCs. Specifically, two in vitro assays were developed: 1) A liver explant assay to assess effects of EDCs that can interact with the estrogen receptor (environmental estrogens), and 2) a gonadal explant assay to assess effects of EDCs on sex-steroid production. The test species selected were northern pike (Esox lucius), walleye (Sander vitreus), and white sucker (Catostomus commersoni) that were sampled from Lake Diefenbaker, Saskatchewan, Canada, and white sturgeon (Acipenser transmontanus) that were randomly selected from an in house stock reared from eggs. Liver tissue was excised from male fishes and exposed for 24 h to a synthetic estrogen, 17α- ethinylestradiol (EE2). Transcript abundance of vitellogenin (VTG), estrogen receptor (ER) α and β in liver tissue were quantified using qPCR. Gonad tissue from both male and female were excised and exposed for 24 h to a model inducer (forskolin) and inhibitor (prochloraz) of steroidogenesis. 11-ketotestosterone (11-KT) and estradiol (E2) were quantified in media by use of ELISA. Exposure to EE2 resulted in a concentration dependent increase in VTG in all species, and an increase in ERα in northern pike. Walleye males showed the greatest sensitivity to EE2. Gonad tissues exposed to forskolin showed a concentration dependent increase in 11-KT and E2. Exposure to prochloraz resulted in a decrease of 11-KTand E2. Male and female white sucker showed greatest sensitivity to forskolin, while male and female walleye showed greatest sensitivity to prochloraz. The seasonal time point during which gonad explants were excised and exposed had an impact on the potency and magnitude of response, resulting in a seasonal effect on sensitivity. Also, gonad explants from these species were found to have greater sensitivity than responses previously reported for in vitro explants of other fish species such as the fathead minnow (Pimephales promelas), and stable cell lines currently used as screening applications to detect chemicals that might disrupt the endocrine system. Therefore, current approaches that use stable cell lines or tissue explants from standardized small bodied laboratory species might not be protective of some wild fish species. These tissue explants represent a promising approach to help understand species sensitivity to EDCs, and if appropriately validated, could be a powerful tool for chemical screening.

Environmental factors affect fish distribution and fisher behavior. These factors are seldom included in stock assessment models, resulting in potentially inaccurate fish abundance estimates. This study determined the impact of these factors using the commercial catch rate of sauger (Sander canadensis) and walleye (Sander vitreus) in Lake Winnipeg by: (1) the use of satellite data to monitor turbidity and its impact on catch via simple linear regression and (2) the effect of environment on catch and effort using generalized linear models. No statistically significant relationship was found between catch and turbidity; a result which may be due to small sample sizes, the fish species' examined, and variable turbidity at depth. Decreased effort was correlated with harsh weather and decreased walleye catch. Increased walleye catch was correlated with low temperature and low Red River discharge. Increased sauger catch was correlated with high temperature, high cloud opacity, and average Red River discharge.

Environmental factors affect fish distribution and fisher behavior. These factors are seldom included in stock assessment models, resulting in potentially inaccurate fish abundance estimates. This study determined the impact of these factors using the commercial catch rate of sauger (Sander canadensis) and walleye (Sander vitreus) in Lake Winnipeg by: (1) the use of satellite data to monitor turbidity and its impact on catch via simple linear regression and (2) the effect of environment on catch and effort using generalized linear models. No statistically significant relationship was found between catch and turbidity; a result which may be due to small sample sizes, the fish species' examined, and variable turbidity at depth. Decreased effort was correlated with harsh weather and decreased walleye catch. Increased walleye catch was correlated with low temperature and low Red River discharge. Increased sauger catch was correlated with high temperature, high cloud opacity, and average Red River discharge.

The rheological, color, micro-structural, and electrical properties of surimi seafood gels were investigated. Various starches and protein additives at different ratios were evaluated with Alaska pollock surimi under ohmic heating at different heating rates to determine their functional properties and further to compare these properties with those of conventionally cooked gels. Native starches at low concentration were able to enhance rheological properties due to their gelatinization during heating. Pregelatinized starch decreased texture properties; however, it could suppress the undesirable appearance of the final product because its granules could absorb the surrounding water during chopping and perform a higher degree of retrogradation when cooling. A mixture of native and pregelatinized starches showed a positive trend at high concentration. The more starch added, the lower the L* and b* values of the gels. Protein additives improved textural properties, but negatively affected gel colors. Lower moisture content of the final products showed higher strength in texture, but lower lightness values. Gels cooked under ohmic heating with a slow heating rate mostly exhibited better texture properties than conventionally cooked gels. Electrical conductivities increased when temperature increased, resulting in a linear relationship. Electrical conductivity also significantly increased with moisture content, and slightly increased with applied frequency and voltage. There were some changes in the magnitude of electrical conductivity of surimi-starch paste when temperature increased, most obviously seen at a high concentration of native starch with slow ohmic heating. This indicated that starch gelatinization affected the electrical conductivity of surimi-starch paste while heating. / Graduation date: 2003

Includes bibliographical references. / "Submitted to Ohio Division of Wildlife." "The first objective was to determine the accuracy of field identification of individual fish to species and to assess the extent of hybridization between walleye and sauger ... The second objective was to assess genetic variation in both species ... " -- p.3. Also available in print.

Thesis (Ph.D.)--Ohio University, November, 2004. / Includes bibliographical references (leaves 115-128)