Larval Yellow Perch (Perca flavescens), Alewife (Alosa pseudoharengus), and Predatory Zooplankton Distributions in Response to Fine-Scale Temperature Pattern in near-Shore Lake Michigan

Yellow perch (Perca flavescens) and alewife (Alosa pseudoharengus) are ecologically and economically important species in Lake Michigan; however, despite their significance, mechanisms controlling early life survival and subsequent recruitment of both species remain elusive.  Along with larval yellow perch and alewife, three species of predatory zooplankton, Leptodora kindtii (native), Bythotrephes longimanus (invasive), and Cercopagis pengoi (invasive), inhabit the near-shore areas of Lake Michigan.  While these predatory zooplankton are hypothesized to compete with larval fish in near-shore Lake Michigan, the potential for competition may be limited by their spatiotemporal overlap.  Near-shore Lake Michigan is a highly dynamic environment characterized by rapid temperature fluctuations which undoubtedly influence icthyoplankton and zooplankton distributions.  We examined spatiotemporal distributions of larval yellow perch, larval alewife, and predatory zooplankton in near-shore Lake Michigan and quantified biotic and abiotic factors influencing there distribution.  We sampled larval fish, zooplankton, and measured temperature along a southern Lake Michigan transect on every third to fourth day during May-July 2010.  Yellow perch began emerging in late May and persisted until mid-June while alewives began emerging in early June and persisted throughout July.  Predatory zooplankton were present throughout the sampling period with greatest abundances occurring between mid-June and July.  During the study time period we observed rapid changes in thermal conditions in near-shore Lake Michigan which seemingly influenced distribution of both larval fish and predatory zooplankton.  Understanding how near-shore physical processes structure distribution and vital rates of important Great Lakes fish larvae should help explicate their recruitment dynamics and facilitate proactive Great Lakes management.