Date of Award
Master of Science (MS) in Biology
A. R. Black
The purpose of this research was to assess the impacts of invasive fishes on wetland communities. Within this study we explored fish effects on the invertebrate constituents of these wetlands, and possible niche overlap of fish and dabbling waterfowl using stable isotope analysis. Brook stickleback (Culaea inconstans) and pumpkinseed (Lipomis gibbosus) pose a potentially growing threat to temperate Pacific drainages of North America due to their ability to outcompete native fauna. Our study compares and contrasts the invertebrate constituents, their diversity, abundances, and stable isotope ecology among fish invaded and non-invaded wetlands. We found that brook stickleback and pumpkinseed are having limited effects on the invertebrate communities of these wetlands, however stickleback appear to have a greater effect on these communities than pumpkinseed. When comparing stickleback and pumpkinseed ponds collectively against fish free ponds we find only three invertebrate taxa are significantly affected, branchiopods, coenagrionids, and baetid mayflies. However when we compare the presence of stickleback versus no stickleback we find several differences among taxa abundance and evenness. Evenness among invertebrate communities within stickleback and no stickleback ponds was significantly different while diversity and richness were comparable among ponds. Fish free ponds exhibited higher evenness values (E=0.6) among taxa than stickleback invaded ponds (E=0.4). Among the 20 most common littoral taxa, bivalves, chironomids, Chaoborus, oligochaetes, coenagrionids, and baetid mayflies were found to significantly vary in abundance. Our stable isotope analysis found evidence to suggest potential niche overlap between waterfowl and stickleback; assessment of δ13C ratios between stickleback, sampled duck feathers, and duck blood were significantly different indicating different dietary sources. Analysis of δ15N between stickleback and waterfowl feather samples show that these two species occupy similar trophic levels; however p-values suggest these tissues are not highly alike. When comparing δ15N among stickleback and duck blood samples we see these two species occupy significantly different trophic levels. However, sticklebacks appear to be generalists in their diets, showing evidence of both pelagic (depleted δ13C) and littoral (enriched δ13C) carbon sources. This generalist diet allows for some degree of potential overlap and possible competition effects with waterfowl. Pumpkinseeds show potential niche overlap with waterfowl as they possess similar carbon resource signatures. Pumpkinseed tissues compared to duck feather and blood samples were not found to vary significantly for δ13C. Duck blood samples for δ15N proved to be significantly different from pumpkinseed tissues. Nitrogen analysis between waterfowl feathers and pumpkinseed show no significant differences, indicating that waterfowl and pumpkinseed share similar trophic levels as well as diets and the potential for competition exists.
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Bridges, Levi, "Invasive fish effects on the invertebrate constituents of wetland communities" (2011). EWU Masters Thesis Collection. 2.