A reported decline in Arctic grayling (Thymallus arcticus) caused the Alaskan State Board of Fisheries to close sport grayling fishing at the Ugashik Narrows, Alaska, in 1990. Sport fishing did not appear to have caused the reported decline; the decline occurred during a period with negligible harvest (Meyer 1990). My objective was to evaluate whether the decline might be an artifact associated with fish movements. I determined locational fidelity between years and persistence of occupation of individual areas and grayling population structure over time. Changes in population structure are circumstantial evidence that movement is occurring. The following factors may effect population parameters: (1) the movement of grayling into and out of the Narrows and (2) periodic displacement of grayling from the Narrows during spawning and migration of sockeye salmon (Oncorhynchus nerka). Therefore, a single sampling effort may seriously underestimate the population.

<p>Invasive fishes frequently change natural aquatic habitats due to predation and competition. The Alaska blackfish (Dallia pectoralis) is indigenous to some regions of Alaska but was illegally introduced to the Cook Inlet Basin in the 1950s. By the 1970s, fisheries managers expressed concern over possible ecosystem-altering effects of the blackfish introduction, especially in waterbodies containing popular sport fish. Descriptive food habit studies may assist fisheries managers in making decisions regarding management of non-native populations of Alaska blackfish. This project characterizes diet of three Cook Inlet Basin Alaska blackfish populations through stomach contents analysis. Shifts in diet across season, sex, and size of individuals from a lake, wetland pond, and stream are discussed using the Index of Relative Importance. Cook Inlet Basin Alaska blackfish consume similar invertebrate prey as native juvenile salmonids and stickleback, with major prey consisting of epiphytic/benthic dipteran larvae, gastropods, and ostracods. Piscivory, including cannibalism, is infrequent in these populations. Due to the high degree of dietary overlap with native fishes and stocked sport fish, and evidence that many Cook Inlet Basin waterbodies contain established populations of Alaska blackfish, fisheries managers should take actions to restrict the spread of blackfish through public awareness education, law enforcement, and funding for additional research. An Alaska blackfish husbandry manual outlines closed-system rearing and artificial fertilization protocols useful to researchers and educators for keeping live Alaska blackfish in the laboratory and classroom, in order to add to our body of knowledge about this species.

<p> Limited information exists on how southern Californian restored estuaries affect fish habitat use. I used the movements of five predatory fishes in two guilds (ambush and roving predators) to assess juvenile habitat use within estuaries and across landscapes at two spatial scales. Translocating fishes between two discrete estuaries located approximately I 0 km apart revealed that connectivity potential between sites differed between foraging guilds. Despite habitat design differences, fishes did not appear to prefer one site over the other. However on a smaller scale (e.g., within a single estuary), differences in microhabitat conditions affected the habitat use by California Halibut (<i>Paralichthys californicus</i>). Individuals selected habitat based on water flow velocity, temperature and eelgrass coverage, but utilized habitat conditions in a size-segregated manner. Since restoration habitat design influences available microhabitat conditions, differences in design likely alters space use within restored estuaries although perhaps not estuary selection itself.</p>

Thesis (Ph.D.)--North Carolina State University, 2006. / (UnM)AAI3223189. Adviser: David B. Eggleston. Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 2996.

Thesis (Ph.D.)--University of Washington, 2007. / (UMI)AAI3265389. Source: Dissertation Abstracts International, Volume: 68-05, Section: A, page: 2028. Adviser: Eric A. Smith.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2684. Adviser: Scott Willenbrock. Includes bibliographical references (leaves 92-97) Available on microfilm from Pro Quest Information and Learning.

Metaphyton is a poorly studied algal community that can develop into large floating mats in rivers, wetlands and lakes. In this thesis, I examined the role of nutrients in determining differences in metaphyton biomass both seasonally and spatially within a lowland temperate river, the Rideau River, Ontario. The source of nutrients was also examined by analyzing the stable isotope signature of the mats in relation to adjacent land-use. Metaphyton in the river was restricted to slow-flowing areas of the littoral zone and was mainly comprised of filamentous green algae (Spirogyra and Cladophora). From the results of this study, conditions for the presence of large metaphyton communities in rivers include: (1) shallow littoral zones with minimal current, (2) the presence of macrophytes (as a substratum), and (3) moderate to high nutrient concentrations (particularly dissolved inorganic nitrogen). To control metaphyton in the Rideau River, the nitrogen loading to the system must be considered as well as phosphorus. (Abstract shortened by UMI.)

We conducted an experiment to determine the effects of cage aquaculture on the functional properties of a lake. We installed a commercial aquaculture operation into a lake located within a pristine headwater region of the boreal shield. We used a before-after control-impact design to evaluate the weight of evidence for causal effects. We quantified sinks, sources and exchanges of carbon, nitrogen and phosphorus to the lake and presented this information in a budget format. We then calculated retention rates for these chemicals and compared them to integral amounts of carbon, nitrogen and phosphorus accumulating in the water column. We also measured removal rates (sedimentation) of these elements from the water column and transformation rates (primary production) within the water column. We found that the amounts of nitrogen and phosphorus retained in the lake increased dramatically during farm operation. With the exception of an increase in particulate carbon, we did not observe an accumulation of these chemicals in the water column. We did however observe lake wide increases in carbon and nitrogen sedimentation. Primary production increased significantly in the aquaculture-impacted lake and the period of peak productivity shifted to later in the summer. We discuss our results in the context of consequences to aquatic life and source water and we provide some recommendations for management.

Methylmercury (MeHg) is a toxic heavy metal and a health threat to wildlife and humans, however nothing is known about its effects on amphibians. MeHg is produced from inorganic Hg in the aquatic environment, and bioaccumulates in the food chain. This exposes tadpoles to elevated levels of MeHg in their diet, and may pose a risk to development. Tadpoles of the North American species Bufo americanus and Rana pipiens as well as the African frog model species Xenopus tropicalis were subchronically exposed to dietary McHg ranging in concentration from 1ng/g to 1000 ng/g to determine LC50s and species sensitivity differences. A developmental differences study was also performed with B. americanus. The 33-day LC50 estimates indicate that Gosner stage 25 tadpoles of both B. americanus and R. pipiens were the most sensitive, and they exhibited a similar sensitivity to McHg toxicity. The X. tropicales LC50 estimate is significantly higher (p=0.05) than those calculated for B. americanus and R. pipiens Gosner stage 25, and the developmentally advanced B. americanus Gosner stage 27-30 LC50 estimate is also significantly higher (p=0.05) than the B. americanus Gosner stage 25 LC50. (Abstract shortened by UMI.)

Fish are becoming more important in the human diet as they represent a high protein source and a source of essential free fatty acids. Fish production from aquaculture has been improved by the selection of faster growing individuals, but fish continue to remain an expensive nutrient source. A better understanding of fish growth mechanisms and regulation will help to further improve aquaculture techniques. Moreover, studying those factors that stimulate cells implicated in fish muscle growth could provide useful knowledge and possible applications in mammalian muscle illness. In contrast to mammals and birds, fish growth is generally indeterminate and most fish grow throughout their life by the formation of new muscle cells (hyperplasia) and/or by increasing muscle cell volume (hypertrophy). Proliferation and differentiation of muscle cells are regulated by transcription factors called myogenic regulatory factors (MRF). MyoD and myogenin are MRF involved in cell proliferation and differentiation in vertebrates. Many factors affect fish growth including external factors such as temperature and food availability, and internal factors, principally hormones. The effects of temperature on fish growth and metabolism were assessed in Atlantic cod (Gadus morhua) and rainbow trout (Oncorhynchus mykiss ), and the effects of hormones were investigated using Atlantic salmon (Salmo salar) made transgenic for growth hormone (GH) and rainbow trout fed beta-agonists. In order to understand the mechanisms and regulation of myogenesis, morphometric parameters were recorded, metabolic enzymes were assayed in liver and skeletal muscle and myogenesis was measured in white and red muscles in each experiment. Moreover, several growth factors and hormones were tested in vitro on myosatellite cell proliferation and differentiation. The results demonstrate that metabolism and myogenesis are not affected by the same factors, and an increase in growth is not absolutely accompanied by an effect on tissue metabolism. High and constant water temperatures increased juvenile cod growth though there were no significant alterations in liver and white muscle metabolism. In contrast, factors such as photoperiod and internal cycles appear to be more important in the control of cod tissue metabolism. However, myogenesis was significantly decreased and metabolism increased in rainbow trout exposed to cold compared with high temperatures. Growth hormone, insulin-like-growth factor I (IGF-1) and fibroblast growth factor (FGF) were found to increase in vitro myosatellite cell proliferation in salmonids. My results also show that proliferation and differentiation of salmon muscle does not happen simultaneously but may alternate in red and white muscles. These results taken together contribute to a better understanding offish muscle growth and metabolism and will be used in future studies to optimize fish growth in aquaculture.