Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 60-63). Also available on the World Wide Web.

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). "June 2006." Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references. Online version available on the World Wide Web.

49 leaves ; 29 cm Typescript Thesis (M.S.)--University of Oregon, 1974 Includes bibliographical references (leaves 45-49) Unif. Title University of Oregon theses, Dept. of Biology, M.S., 1974

A pre-requisite for the formulation of a responsible fisheries management programme for an aquatic ecosystem is a comprehensive fish ecological study, which focuses on the various ecological and biological aspects of the fish population and related fisheries data. The fish ecological and fisheries data must be considered during the decision making process of management. The freshwater fish of the Eastern Caprivi, Namibia, has enormous value in terms of the local subsistence fishery. Fish is an affordable protein source in this region, and is of socioeconomic importance, as it generates income for up to 82% of the local households. Unfortunately commercialisation of the resource is becoming more and more prevalent in this region, as local commercial fishermen take advantage of the readily available fish resource, by the callous use of non-selective fishing gears such as drag nets. Unregulated fishing methods, such as the use of drag nets, is detrimental to the fish population and ecology of an aquatic ecosystem. The Ministry of Fisheries and Marine Resources (MFMR), Namibia, recognised the need for a fisheries management programme in the Eastern Caprivi region. Proper fisheries legislation, in terms of the recommended fishing gears which may be used by local fishermen, is however needed to achieve the goals set by such a management programme. The MFMR realised the need for a comprehensive fish ecological study in the Eastern Caprivi, which would thus aid in the formulation of legislation measures. Five, flood related, fish ecological surveys were consequently conducted in the Eastern Caprivi, between 1997 to 1999. The relevant ecological, biological, and fisheries data was gathered. This data will lay the basis for future studies in this region, and will aid management in their decision making process. Results derived from the experimental gill net data is of the most importance in the formulation of fisheries legislation. The data collected in the Eastern Caprivi was processed and the results presented and discussed in this study. Conclusions are made concerning the biological and ecological aspects of the fish species and the fish population. Recommendations, concerning the fisheries data, are made to the management of the Ministry of Fisheries and Marine Resources in aid of their legislation process. The Eastern Caprivi is a productive and intricate wetland system, consisting of rivers, floodplains, canals, lakes, swamps and marshlands. Three perennial rivers, the Zambezi, Chobe, and Kwando Rivers with their associated floodplains were studied. A total of 82 fish species occur in the Eastern Caprivi, of which 69 were recorded during this study / Prof. G.J. Steyn

D.Phil.

No description available.

Life histories, trophic dynamics , abundances, and microdistrubution of Trichptera were investigated in the Flathead River, Montana, from January 1977 through August 1979. Thirty-six Trichoptera species representing 9 families were collected from 5th order tributaries and the 6th order Mainstream River.

Forested streams are closely linked to terrestrial catchments which affects their biogeochemical cycling and carbon inputs. Catchment disturbances alter stream water quality and food webs, including changes in productivity. Such changes in stream conditions can potentially alter consumers’ reliance on autochthonous (in-stream) or allochthonous (terrestrial) sources and mercury bioaccumulation. A recent outbreak of the spruce budworm (SBW) that feeds on spruce and fir trees has provided the unique opportunity to examine stream food web responses across watersheds experiencing a range of defoliation in the Gaspé Peninsula, Québec. This project compares streams in twelve watersheds which were selectively sprayed to control SBW and create a gradient in defoliation. Food web samples (food sources, invertebrates, fish) were analyzed for stable isotopes of carbon and nitrogen in 2019 and 2020 to characterize food web structure, and algal productivity was measured in 2019. Hierarchical partitioning models were used throughout the study to compare the contributions of various local and landscape conditions to stream responses. Models indicated that watershed defoliation contributed to increasing autochthonous production, although some invertebrates were more allochthonous in heavily defoliated watersheds, and brook diets were unaffected by defoliation. Next, food web samples were analyzed for methylmercury (food sources, invertebrates) or total mercury (fish) and trophic magnification slopes were determined for each stream food web. Mercury levels in carnivorous invertebrates and brook trout were driven by dissolved organic carbon (DOC), but not consumer autochthony or watershed defoliation. Additionally, rates of trophic magnification were not related to defoliation severity or DOC. This study found that defoliation contributed to increasing autochthonous production and invertebrate consumer allochthony. However, this disturbance did not increase consumer mercury levels or biomagnification in stream food webs. These findings suggest that intervention to reduce defoliation would mitigate algal responses and dietary shifts, but not mercury cycling as it is influenced by DOC levels in the streams of this region. / Thesis / Master of Science (MSc) / A recent spruce budworm outbreak is causing widespread defoliation of spruce and fir trees, but the impacts to stream environments, including primary production, its consumption, and contaminant levels, are largely unknown. Streams are sensitive to conditions in the surrounding terrestrial environment, as such changes can affect the diets of stream invertebrates and fish and are also linked to increased contaminant levels in aquatic organisms. Specifically, mercury is a metal that is transferred through diet and can reach toxic levels in fish. This study found that defoliation is contributing to increased algal production in streams in the Gaspé Peninsula, Québec. However, some stream invertebrates consumed more terrestrial material in streams that had heavier defoliation. Furthermore, defoliation and algal diets did not increase levels of mercury in aquatic organisms, but this contaminant was affected by increasing concentrations of dissolved organic carbon in the streams. These findings suggest that forest defoliation can alter organisms’ diets but not mercury levels.

The adequacy of the negative exponential model with one independent variable, days or accumulated time, as a descriptive equation for aquatic leaf litter processing was examined. The effect of adding a second independent variable, degree days or accumulated temperature, to the model was also examined. The two variable negative exponential model was shown to have at least two advantages over the single variable model. The two variable model adequately fits litter processing data for more cases than the single variable model. The expanded model also allows determination of rate coefficients for various temperature levels of the experiment rather than assuming a single, constant rate coefficient as the simpler model does. The trends of the temperature dependent rate coefficient can be used to examine processing differences between experiments for different sites and seasons.