The Influence of Food Web Dynamics On the Growth and Production of Lahontan Cutthroat Trout, in Pyramid Lake, NV

Quantifying interactions between species is integral for understanding the structure of aquatic food webs and can aid in understanding how species will respond to environmental variability.  Lahontan cutthroat trout, Oncorhynchus clarkii henshawi (LCT), currently occupy 0.4% of their native lacustrine habitat and are listed as threatened under the ESA.  Since extirpation of naturally-reproducing individuals in 1942, LCT in Pyramid Lake have been maintained through stocking programs; however, these hatchery LCT fail to reach pre-extirpation sizes.  We hypothesized that: 1) LCT are food and perhaps gape limited, and 2) LCT may compete with exotic Sacramento perch for tui chub as a food resource.  While catch data suggests only moderate overlap in distribution, diet and isotope data indicate considerable overlap in the trophic niches of LCT and Sacramento perch.  However, bioenergetic simulations indicate that annually, Sacramento perch only consume 5% of what LCT consume lake-wide, perhaps due to gape limitation.  In addition, on an annual basis, LCT consume only 80% of the tui chub available lake-wide, suggesting that LCT are not food limited.  In addition to management implications, this study highlights the importance of understanding the dynamic interactions of multiple energetic constraints on a community member.