Date of Award:

5-2017

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Department name when degree awarded

Watershed Sciences and the Ecology Center

Committee Chair(s)

Jereme Gaeta

Committee

Jereme Gaeta

Committee

Phaedra Budy

Committee

Dan MacNulty

Abstract

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 structure is established. The ability of invasive species to outcompete and prey upon native species are two characteristics that make them a leading cause of fish extinctions in North America.

Northern pike (Esox lucius; hereafter pike) are voracious ambush top predators \native to the upper Midwest and Mid-Atlantic regions of the lower 48 United States, Alaska, and southern Canada. Pike have been spreading across the Intermountain West and Pacific Northwest and were detected in 2010 in Utah Lake, UT, a highly degraded ecosystem home to the endemic, endangered June sucker (Chasmistes liorus). June suckers are an important indicator species for the lake, meaning they can signal a change in the biological or physical condition of the ecosystem and serve as a measurement of ecosystem health. Captive breeding programs, stocking programs, and habitat restoration projects are major components of the estimated $50 million-dollar plan to restore the June sucker population. The recent introduction of invasive pike may not only threaten the success of June sucker restoration, but also their downlisting from endangered to threatened.

We tested whether pike predation could hinder the restoration efforts of June sucker., 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 each year. 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 removal 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. Our age-structured population model suggests the pike population will stabilize 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 preventing the spread of aquatic invasive species and the need for aquatic invasive species education.

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