Freshwater systems are among the world’s most valuable and imperiled ecosystems, and fishes in the southwestern US are one of these critically imperiled groups. This dissertation addresses information gaps surrounding ecosystem restoration in an effort to assist desert fish conservation. I begin with a literature review of the potential threat that hybridization may pose to fishes in the order Cypriniformes, to which most fish species in the southwest belong. We document multiple incidents where habitat overlap in southwestern species groups has resulted in hybridization. We advocate for several management changes, including monitoring of the genetic makeup of both native and introduced stocks to look for evidence of hybridization or introgression. My second chapter seeks to improve stable isotopes of hydrogen as a tool to distinguish between primary producers in aquatic food webs. We found that fish assimilated hydrogen from water, constituting 23 ± 2.7% of total fish tissue hydrogen. Fish also discriminated against deuterium (δ2H = –28%) during tissue assimilation, though it was not clear whether this discrimination was from food or water. Next, I utilized the restoration of Fossil Creek, AZ, to examine the impacts of flow restoration and exotic fish removal the food web. We measured food web relationships before and after the 2004 restoration of Fossil Creek, Arizona. We found that the percentage of algae-derived hydrogen in fish tissue increased 10.2% in response to water flow restoration. The trophic position of native fishes increased with the removal of exotic fishes (average nitrogen signal increase of 1.8‰). Finally, I examined the feeding behavior in two suckers species with distinct jaw morphologies: the Sonora sucker (Catostomus insignis), a generalist carnivore, and desert sucker (Pantosteous clarkii) a specialized algae scraper. Counter to our predictions, both species were able to alter key aspects of feeding behavior, depending on the location and type of the prey offered. These results suggest that the two sucker species may compete more for food resources than would be expected based on the ecomorphological paradigm.
|Advisor:||Gibb, Alice C.|
|Commitee:||Hungate, Bruce A., Marks, Jane C., Sisk, Thomas D.|
|School:||Northern Arizona University|
|School Location:||United States -- Arizona|
|Source:||DAI-B 75/04(E), Dissertation Abstracts International|
|Subjects:||Ecology, Conservation, Physiology, Aquatic sciences|
|Keywords:||Conservation, Functional morphology, Native fish, Restoration ecology, Stable isotope analysis, Stream restoration|
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