Spatial Variation in Nearshore Fish Community and Age Structure in Southwest Lake Michigan

Nearshore habitats in Lake Michigan vary sharply in terms of substrate, structural complexity, and thermal regime.  Despite these differences, research and management of fish communities has largely considered the nearshore region of Lake Michigan as a homogenous unit.  Nearshore habitat diversity can affect food web interactions as well as fish growth and recruitment.  To look at abundance and growth rate differences in relation to habitat types, three distinct locations in Illinois waters of Lake Michigan were sampled bi-monthly from 2008-2012 using small-mesh gill nets.  Round goby catch rates were positively related to structural complexity, with almost no fish caught at the sandy location and highest catch rates occurring at the location containing boulders and cobble.  Alewife catch rates were highest at the cool northern location and lowest at the warmer southern location.  Perch catch rates varied by month, with incoming pulses of age-0 fish in August being higher at the northern location, but age-1 yellow perch in the spring being more common at the southern location.  Significant annual variation was found in total length at age-0 for yellow perch, which indicates that temporal patterns in biotic or abiotic conditions could be more important than spatial factors for juvenile perch growth.