Prey Availability during the Larval Period Regulates Recruitment: Evidence for the Match-Mismatch Hypothesis

It has long been recognized that zooplankton timing and abundance during the larval period can play a major role in recruitment strength of fishes.  In Lake Erie, Walleye Sander vitreus have experienced weak recruitment since the 2003 year-class, with explanations for declines in recruitment strength remaining elusive.  Therefore our study focused on the role of zooplankton temporal availability, size, and density on Walleye recruitment, and how that role may have changed through time.  Specifically, we used data on zooplankton and larval Walleye availability over a 9-year period (i.e., 1994-1999 and 2011–2013) to elucidate patterns during years of strong (ex., 1994 and 1996) and weak recruitment (ex., 2011-13). While larval walleye abundance did not differ between periods, average zooplankton density decreased by 85%. Correspondingly, walleye larvae exhibited slower mean growth rates and reduced recruitment to the age-0 juvenile stage.  We found measures of prey quality and quantity to explain 85-96% of the variance in recruitment, providing compelling support for the Match-Mismatch Hypothesis occurring in a large lake ecosystem.  Our findings highlight the relevance of marine fish recruitment hypotheses to freshwater ecosystems and encourage a continued cross-fertilization of ideas between the two areas of research.