Date of Award:
Master of Science (MS)
Native fishes of the Colorado River Basin have experienced dramatic reductions in range and abundance as a result of extensive human alterations to the basin’s waterways. Many of these native fishes are federally listed under the Endangered Species Act, while several others are subject to range-wide conservation agreements between state and federal management agencies. Three of the native species subject to range-wide conservation agreements are the flannelmouth sucker, bluehead sucker, and roundtail chub (hereafter, the “three species”). Each of the “three species” is still found in the San Rafael River of southeastern Utah, which has experienced habitat degradation and non-native species establishment representative of many desert streams.
In this study, I examined the effects of non-native species on the food web structure and relative growth rates of the “three species” (Chapter 2) in two sections of the river characterized by the presence and absence of non-native fish. I found that the presence of non-native species lengthens the food chain, presenting new predators and competitors to the ‘three species.’ However, I found no evidence of reduced growth in the presence of these non-native fishes, likely due to movement of individuals of the “three species” between the two sections of river. Secondly, I developed a model to identify and rank limiting factors to the “three species” along the continuum of the lower river. Finally, I used this model to simulate and predict the relative effect of different restoration actions at different locations along the river on the abundance of the ‘three species.’ These models predicted that removal of non-native fishes and the restoration of long stretches of suitable habitat would be most beneficial to the ‘three species.’ Models such as those developed in this study can be useful for management agencies to prioritize restoration efforts to ensure the persistence of the “three species” both in the San Rafael River and throughout their historic range.
Walsworth, Timothy E., "Analysis of Food Web Effects of Non-Native Fishes and Evaluation of Stream Restoration Potential for the San Rafael River, Utah" (2011). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 1095.
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