Event Title

An Energetic Assessment of Predator Consumption in Utah Lake with Consideration of Future Options for June Sucker Recovery

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-2-2009 8:00 AM

End Date

4-2-2009 8:05 AM

Description

The prolific invasion of nonnative piscivores to Utah Lake is considered a major impediment to recovery of the endangered June sucker. Our overall goal was to estimate predator consumption rates of the nonnative piscivorous fishes that currently dominate Utah Lake and to evaluate their potential impact on June suckers and other prey under current conditions and potential future management options. We synthesized all available information on lake temperature regime and the size, growth, and diet of walleye, catfish, white bass, and crappie as inputs into a bioenergetics analysis of predator consumption across one year, representing "current" conditions. We extrapolated our estimates of individual predator consumption to a population level using relative CPUE as a surrogate for abundance. Lastly, we compared isotopic-derived trophic position to diet composition, and re-ran a subset of model scenarios accordingly. Dominant predators (e.g., white bass, walleye, and catfish) consumed a high proportion of white bass, perch, carp, and crappie. However, unidentified fish in the diet make up a substantial portion of predator consumption; if even a small portion of the unidentified fish component is suckers, predatory impact on June suckers is likely significant. In addition, our predictions of predator consumption under a low carp abundance scenario (i.e., after removal) suggest that in years of poor recruitment of other predominant prey items (e.g., white bass and crappie), some predators may switch prey and consume a higher concentration of June suckers. Our comparison of isotopic-derived position to diet data indicated that: 1) Utah Lake is characterized by two primary pathways, a more pelagic food web and a more littoral food web, and 2) there appears to be fairly close correspondence between isotope-derived trophic position and diet composition for large top piscivores, and 3) more generalists (e.g., white bass) appear to be eating more fish (and potentially June suckers) than appears in the static diet samples. Lastly, we note that current modeling evaluations of the potential effects of different management scenarios are extremely limited by the lack of abundance information for almost all fishes of Utah Lake. Obtaining reliable estimates of relative abundance should be a top priority for future monitoring.

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Apr 2nd, 8:00 AM Apr 2nd, 8:05 AM

An Energetic Assessment of Predator Consumption in Utah Lake with Consideration of Future Options for June Sucker Recovery

Eccles Conference Center

The prolific invasion of nonnative piscivores to Utah Lake is considered a major impediment to recovery of the endangered June sucker. Our overall goal was to estimate predator consumption rates of the nonnative piscivorous fishes that currently dominate Utah Lake and to evaluate their potential impact on June suckers and other prey under current conditions and potential future management options. We synthesized all available information on lake temperature regime and the size, growth, and diet of walleye, catfish, white bass, and crappie as inputs into a bioenergetics analysis of predator consumption across one year, representing "current" conditions. We extrapolated our estimates of individual predator consumption to a population level using relative CPUE as a surrogate for abundance. Lastly, we compared isotopic-derived trophic position to diet composition, and re-ran a subset of model scenarios accordingly. Dominant predators (e.g., white bass, walleye, and catfish) consumed a high proportion of white bass, perch, carp, and crappie. However, unidentified fish in the diet make up a substantial portion of predator consumption; if even a small portion of the unidentified fish component is suckers, predatory impact on June suckers is likely significant. In addition, our predictions of predator consumption under a low carp abundance scenario (i.e., after removal) suggest that in years of poor recruitment of other predominant prey items (e.g., white bass and crappie), some predators may switch prey and consume a higher concentration of June suckers. Our comparison of isotopic-derived position to diet data indicated that: 1) Utah Lake is characterized by two primary pathways, a more pelagic food web and a more littoral food web, and 2) there appears to be fairly close correspondence between isotope-derived trophic position and diet composition for large top piscivores, and 3) more generalists (e.g., white bass) appear to be eating more fish (and potentially June suckers) than appears in the static diet samples. Lastly, we note that current modeling evaluations of the potential effects of different management scenarios are extremely limited by the lack of abundance information for almost all fishes of Utah Lake. Obtaining reliable estimates of relative abundance should be a top priority for future monitoring.

https://digitalcommons.usu.edu/runoff/2009/AllPosters/37