Methodsįallen Leaf Lake is a glacially formed, small (567 ha), deep (about 125 m maximum depth), monomictic, oligotrophic lake that was historically occupied by Lahontan Cutthroat Trout and which is connected to the larger Lake Tahoe by a single tributary (Taylor Creek). Results of this study will provide information on prey use by recently stocked Cutthroat Trout, may elucidate potential competitive or predatory interactions between Cutthroat Trout and other fishes that have not been previously identified, and will provide data that may be used for comparative purposes following ongoing or future management actions. Specific objectives of this study were to 1) quantify the general dietary characteristics of recently stocked Cutthroat Trout and other fishes in Fallen Leaf Lake, 2) quantify dietary overlap between Cutthroat Trout and other fishes in Fallen Leaf Lake, 3) quantify changes in the trophic characteristics of fishes in Fallen Leaf Lake following Cutthroat Trout stocking, and 4) provide a descriptive characterization of the contemporary food web in Fallen Leaf Lake. Therefore, we sought to provide more inclusive information on trophic characteristics of the aquatic species assemblage in Fallen Leaf Lake. 2009), there is limited information on interactions between recently stocked Cutthroat Trout and other species within the Fallen Leaf Lake food web, and no information on prey use by recently stocked Cutthroat Trout. Although researchers have previously studied the influence of Lake Trout on Cutthroat Trout in Fallen Leaf Lake (i.e., Allen et al. The aim of this study was to provide information on the current characteristics of the Fallen Leaf Lake food web. Fish and Wildlife Service (USFWS) recovery plan for this subspecies, which identifies actions that are considered necessary for recovery and protection of federally listed species, has prioritized reestablishing lacustrine populations ( Coffin and Cowan 1995). Endangered Species Act ( ESA 1973, as amended), Lahontan Cutthroat Trout are no longer present in >90% of their historic range and >99% of historic lacustrine habitat ( Coffin and Cowan 1995). Currently listed as threatened under the U.S. By the mid-20th century Lahontan Cutthroat Trout had been extirpated from the Lake Tahoe Basin due to a suite of anthropogenic perturbations, which included overfishing, timber harvest, loss of access to spawning habitats, and introduction of nonnative species. henshawi was the apex predator throughout their historic range in the Lahontan hydrographic basin of northern Nevada, southeastern Oregon, and northeastern California, which includes the Lake Tahoe Basin of California–Nevada ( Behnke 1992). Additionally, intentional manipulation of the isotopic composition of hatchery-reared fish prior to stocking may be useful for evaluating predation in Fallen Leaf Lake and other systems. Managers should consider the effects of predation by Lake Trout and Brown Trout on Lahontan Cutthroat Trout when developing future management and stocking programs for Fallen Leaf Lake. Lake Trout δ 13C and δ 15N increased following Lahontan Cutthroat Trout stocking, a change consistent with incorporating isotopically enriched Lahontan Cutthroat Trout into their diet. Nonnative Lake Trout Salvelinus namaycush and Brown Trout Salmo trutta are top-level predators in Fallen Leaf Lake and both consumed Lahontan Cutthroat Trout during this study. Diet overlap was greatest between Lahontan Cutthroat Trout and Mountain Whitefish Prosopium williamsoni however, these species exhibited a generalized feeding strategy that may allow them to partition prey resources in order to avoid competitive interactions.

Lahontan Cutthroat Trout preyed on mysid shrimp Mysis diluviana, aquatic insects, terrestrial arthropods, signal crayfish Pacificus leniusculus, and fishes. Therefore, we used a combination of stomach content and stable isotope analyses to evaluate trophic characteristics within the aquatic species assemblage in Fallen Leaf Lake. However, the food web in Fallen Leaf Lake has been altered by the past introduction of nonnative species that may prey on or compete with reintroduced Lahontan Cutthroat Trout. Fisheries managers have stocked Lahontan Cutthroat Trout Oncorhynchus clarkii henshawi into Fallen Leaf Lake, California, since 2002 in an attempt to reestablish a naturally reproducing lacustrine population.

Fallen leaf lake water temperature