Juvenile Steelhead in the Muskegon River: Analysis of Larval Drift and Juvenile Diet

Steelhead (Onchorhynchus mykiss) are an important component of the Lake Michigan ecosystem and provide an important regional fishery. Steelhead populations are heavily supplemented with hatchery stocks due to low production in many coastal Michigan streams. Understanding the early life history is critical to improving wild fish populations. During spring 2010 and 2011 maximum larval steelhead drift varied from 0.259/m³ to 0.045/m³ respectively, with peak drift between May 31 and June 7.  The total estimated numbers of larvae drifting during the two sample periods were higher for 2010 than 2011.  Physical factors, particularly discharge, may account for some of the variation between years. During summer 2011, juvenile diets were dominated by hydropsychids, baetids, midge larvae and adults, and simuliids. Fall diets were dominated by hydropsychid larvae. Juvenile diets averaged more prey items per fish in the fall. Juvenile diets have varied over the past ten years apparently in response to the introduction of zebra mussels. Understanding the relationship between larval drift and annual year class, as well as diet, may provide managers with additional tools to manage steelhead stocks in the Great Lakes region.