Feeding Habits of Yellowstone River Otters on Two Lakes PDF Download

Author: William Ralph Wengeler
Publisher:
ISBN:
Category : Brown trout
Languages : en
Pages : 128

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Book Description
"The introduction of exotic lake trout (Salvelinus namaycush) to Yellowstone Lake in Yellowstone National Park has contributed to a significant decline in the heretofore healthy population of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri). There is great concern not only regarding the persistence of this genetically pure cutthroat subspecies, but also for the potential impacts their disappearance will have on the fish-eating predators of Yellowstone Lake and the surrounding community. Nearby Lewis Lake has no cutthroat trout, but is home to a well-established population of non-native lake trout, brown trout (Salmo trutta), and Utah chub (Gila atraria). We examined the contents of 179 river otter (Lontra canadensis) scats collected along the shores of Yellowstone (n=101) and Lewis Lakes (n=78) in Yellowstone National Park to compare otter dietary habits, especially with regard to the mustelid's utilization of native vs. non-native fish species. We also assessed diets using stable isotopes analysis ... on otters and represenatative prey from both lakes. In addition, we analyzed the isotopic signatures of fur taken from Yellowstone Lake otter specimens collected in the early part of the 20th century before exotic trout were introduced. Fecal analysis indicated that trout were consumed much more frequently by contemporary Yellowstone Lake otters (57% annually) than by otters occupying Lewis Lake (12% annually). The predominant fish found in Lewis Lake otter feces were minnows, presumably Utah chub. Stable isotopes analysis, however, identified longnose suckers (Catostomus catostomus) as the primary fish prey for Yellowstone Lake otters (56% contribution to otter diet), while indicating that otters there are generally preying on neither cutthroat trout nor introduced lake trout. Analysis of stable isotopes also indicated that contemporary Yellowstone Lake otters forage at a lower trophic level ... than their historic counterparts ... Isotopic data from Lewis Lake revealed that brown trout (60% contribution to otter diet) contribute more to otter diets there than local lake trout and Utah chub together (40% combined contribution). This study establishes the importance of alternative prey species to otters foraging on both lakes and supplements the growing body of research demonstrating that lake trout will not constitute a major food source for Yellowstone river otters."--Abstract.