Sierra Nevada Aquatic Research Laboratory

15 Jul, 08 AM - 02 Aug, 01 AM

Sierran Lakes have been historically stocked with non-native fish in order to enhance recreational fishing. Even though most restocking of lakes has ceased, many of the lakes have self-sustaining fish populations. Little concern was initially given to the consequences of introducing non-native species on Sierran Lake ecosystems, but later research showed that fish introductions initiated a top down alteration of lake food webs. Major impacts include a shift towards dominance of smaller sized zooplankton and benthic macroinvertebrate species and extirpation of several amphibian species including the endangered mountain yellow-legged frog. Removal of fish from some lakes to restore populations of the frog and restore the aquatic food webs to pre-introduction conditions has been attempted. Several observations documented the loss and subsequent recovery of two large zooplankton species. One question remains: Have the food webs of lakes where fish were removed returned to their pre-introduction structure or has a new fishless food web developed? Answering this question will aid ongoing efforts to protect the frogs from extinction and contribute to general knowledge regarding the long-term impacts of introduced fish on lake ecosystems. One way to assess changes in food webs through time is to measure stable isotope distributions within an ecosystem. Stable isotope ratios of nitrogen and carbon can be used to elucidate food web structure as well as infer animal diets. Nitrogen isotope ratios can indicate the tropic position of species while the carbon isotope ratios can indicate food sources. My research will further understanding of lake ecosystems and the impact of non-native species introductions on food webs. Stable methods developed in my study may broaden the application of isotope techniques in the conservation and management of aquatic ecosystems.

Visit #21258 @Sierra Nevada Aquatic Research Laboratory

Approved

Under Project # 21662 | Research

Assessment of food web recovery from fish introductions using stable isotopes: Sierra Nevada, California

graduate_student - University of California, Riverside

Reservation Members(s)

Paul Koster Jul 15 - Aug 2, 2010 (19 days)

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Dorm 1 Jul 15 - Aug 2, 2010