Factors Affecting Macrophyte and Fish Distribution in Coastal Wetlands of Georgian Bay

Cvetkovic, M.
M.Sc. Thesis for the Department of Biology, McMaster University


The three studies in this thesis are dedicated to improving knowledge on coastal wetlands of the Great Lakes, particularly those located in Lake Huron, Georgian Bay. The overall goal is to promote the health and conservation of these ecologically threatened ecosystems, which have never been examined in this detail prior to my study.

First I describe the overall ecology of Georgian Bay coastal wetlands with ecological indices that are related to water quality, using sites from the entire shoreline. I also identify the plant and fish species assemblages found throughout the Bay, including the exotic species. The information shows that Georgian Bay wetlands are among the most pristine in the Great Lakes, and that the indices based on water quality and macrophyte communities more accurately depict the health of these ecosystems than the index based on fish communities. In Chapter two I show that the predictive ability of biotic factors (macrophyte assemblages) on fish distribution is stronger than abiotic factors (water quality) on both a regional and basin-wide scale. This is the first study to quantitatively assess the role of aquatic vegetation in fish distribution in Georgian Bay, and reinforces the fact that macrophytes are critical to Great Lakes fish production. Lastly in Chapter three, I quantify the degree of wave and wind action affecting 83 wetlands in the Bay, and show that sites with high exposure significantly affect both plant and fish communities, as well as an ecological index based on macrophyte assemblages. Furthermore, I show that the plant and fish assemblages are different in protected versus exposed sites, and that there are significant relationships between specific plant groups and fish taxa. These results can have significant impacts on index development and application, as well as ecosystem management.

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