Date of Award

5-2014

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology

First Advisor/Chairperson

Dr. Jill B.K. Leonard

Second Advisor

Dr. John Bruggink

Third Advisor

Dr. Tracy Galarowicz

Abstract

The Lake Michigan fish community has undergone many changes due to introduction of non-native species, climate shifts, and management actions. Managers need to understand the time course of these alterations, including the time-frame of impact on the food web in the lake. I used a collection (1999-2012) of diet samples from burbot from eastern Lake Michigan to evaluate temporal alterations in burbot diet with particular attention to non-native vs. native forage. Catch per unit effort (burbot/net · day) decreased from a high of 5.82 burbot/net · day (± 2.19) in 2001 to a low of 0.750 burbot/net · day (± 0.25) in 2010, which is consistent with declining burbot populations throughout the Great Lakes (Gorman and Sitar 2013; Stapanian et al. 2013). The collective contribution of sculpin (Cottus), alewife (Alosa pseudoharengus), and ninespine stickleback (Pungitius pungitius) to burbot diet decreased from ~80% before 2006 to ~15% in 2012. During the same time span, round goby (Neogobius melanostomus) contribution to burbot diet increased from ~0% before 2006 to greater than 60% in 2012, implying nearly a complete diet shift of burbot in just six years. The diet shift suggests a change in feeding behavior from partially pelagic/benthic to almost entirely benthic, and a change in prey consumption from alewife/sculpin to round goby. This shift may and serve as a potential link to move the benthos from a nutrient sink to a nutrient source by utilizing round gobies and moving nutrients up the trophic web.

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