Diet, Feeding Rate, Growth, Mortality, and Production of Juvenile Steelhead in a Lake Michigan Tributary

Abstract

Steelhead Oncorhynchus mykiss support valuable sport fisheries in the Great Lakes but are largely sustained by stocking. In many Great Lakes tributaries, steelhead spawning and nursery habitats are limited by hydropower dams, and natural recruitment may be supplemented by habitats in adjacent coldwater creeks. In 1998–2001, we investigated the potential for natural production of steelhead in the Muskegon River, Michigan, a tributary to Lake Michigan, through analysis of parr diet categories, consumption, growth, survival, and production in the main‐stem Muskegon River and in Bigelow Creek. We used electrofishing surveys to estimate parr growth and survival from changes in fish weight and density over time. We estimated diet from gut content analysis and consumption from bioenergetics model analysis. Average fall density of parr in Bigelow Creek was 20‐fold higher than in the Muskegon River. Average summer daily mortality rate of parr in the Muskegon River was nearly threefold higher than in Bigelow Creek. Overwinter mortality rates of parr were low in both habitats. Few yearling and older parr were present in the Muskegon River relative to Bigelow Creek. Age‐0 parr primarily consumed benthic invertebrates. Macroinvertebrate prey densities were sufficient to support high parr growth rates in both rivers. Parr grew at similar rates but consumed 84% more per day in the Muskegon River, which had higher water temperatures than Bigelow Creek. Age‐0 production was fivefold higher in Bigelow Creek than in the Muskegon River. High mortalities of parr in the Muskegon River were correlated with summer water temperatures exceeding 21°C. Average summer temperatures in Bigelow Creek (17°C) were optimal for parr survival. Our results were consistent with data from other Great Lakes tributaries and suggest that small tributary creek habitats contribute disproportionately to steelhead recruitment from large impounded watersheds by providing optimal thermal refugia for parr during summer.