Continued Utilization of Diporeia By Benthivores: A Diet Comparison of Lake Huron Deepwater Sculpin Between 2003 and 2013

Monitoring fish diets is essential to understanding food web dynamics. Diporeia, a primary food of native benthivores such as Deepwater Sculpin Myoxocephalus thompsoni, declined following the introduction of invasive Dreissena mussels into the Great Lakes. Deepwater Sculpins were collected from 2010 to 2013 from bottom trawl surveys in Lake Huron. A total of 416 Deepwater Sculpin stomachs were examined. Diporeia, Mysis, Bythotrephes, and Chironomidae were consumed regularly as well as sphaerid clams, ostracods, fish eggs, and copepods. The mean number per stomach of Diporeia ranged from 7.2 in 2010 to 3.2 in 2013. The frequency of occurrence of Diporeia varied from 94% in 2010 to 52% in 2013, while the frequency of occurrence of Mysis ranged from 49% in 2010 to 69% in 2013. We compared our results to a previous study from 2003 to 2005. The results from both diet studies suggest Diporeia continue to be utilized as a prey resource by Deepwater Sculpin offshore in Lake Huron and the consumption of Diporeia is inversely related to consumption of Mysis. The continued examination of Deepwater Sculpin diets remains vital to assess food web dynamics and restoration of native fishes that rely on them for food.