Date of Award:
Master of Science (MS)
Invasive species introductions are associated with negative economic and environmental impacts, including reductions in native species populations. Successful invasive species populations often grow rapidly and a new food web equilibrium is established. Invasive, predatory northern pike (Esox lucius; hereafter pike) were detected in 2010 in Utah Lake, UT, a highly-degraded ecosystem home to the endemic, endangered June sucker (Chasmistes liorus). Here we test whether pike predation could hinder the restoration efforts of June sucker using the number of June sucker consumed by pike at various population densities as our metric. More specifically, we considered pike density at which the population could consume all June sucker stocked a critical threshold. Currently the number of naturally recruited June sucker is drastically lower than the number stocked. Thus, the metric we used to determine whether the pike population could hinder the June sucker restoration efforts is the number of pike that could consume the number of June sucker stocked. We combined pike growth and foraging observations with an energy-budget, bioenergetics consumption model to quantify lake-wide pike predation on June sucker. We also used an age-structured density dependent population model to estimate the pike population growth trajectory under various mitigation scenarios. Of 125 pike, we found an average pike consumes 0.8-1.0% June sucker and 40% sport fish. According to our bioenergetics model simulations, a population of adult pike at a very high density (60 pike per hectare) has the potential to consume nearly 6 million age-0 June sucker per year, which is likely more June sucker consumed than exist in the environment. In addition, our model suggests that an adult pike density greater than 1.5 pike per hectare has the potential to consume all June sucker stocked annually. Our age-structured population model suggests the pike population will reach equilibrium around 2026 at between 8 and 12 adult pike per hectare with the potential to consume between 0.8 and 1.2 million age-0 June sucker per year, respectively. The growing pike population could hamper restoration efforts and threaten endangered June sucker, a population with a mere 2,000 adults, in jeopardy of extinction. Our findings not only inform pike management efforts, but also highlight the importance of allocating resources toward habitat restoration to provide refuge for juvenile June sucker from predation, preventing the spread of aquatic invasive species, and the need for aquatic invasive species education.
Reynolds, Jamie, "Predicting the impact of a northern pike (Esox lucius) invasion on endangered June sucker (Chasmistes liorus) and sport fishes in Utah Lake, UT" (2017). All Graduate Theses and Dissertations. 6323.