Larval Habitat Quality As a Determinant of Future Growth and Recruitment

Towards improving our understanding of early life processes to future population demographics, we explored the relationship between spring habitat quality experienced by larval walleye (Sander vitreus), an ecologically and economically important species in western Lake Erie, and size and abundance of juveniles in August, when recruitment to the fishery is set. We hypothesized that a good larval habitat quality would positively correlate with juvenile length and abundance three months later. We used in situ measurements of prey (zooplankton) availability and temperature in a spatially explicit, bioenergetics-based model to create an index of spring larval habitat quality during 1994-2011, which we estimated by calculating an individual’s Growth Rate Potential (GRP).  In so doing, we used water clarity and larval walleye diet data to create a function to estimate foraging rate. Our analyses demonstrated that observed August juvenile abundance was positively correlated with spring GRP. By contrast, growth was negatively correlated with GRP, suggesting that early-life growth rate was density-dependent. Inshore GRP was greater than offshore GRP and positively correlated with springtime Maumee River discharge, pointing to a role for watershed inputs in the recruitment process. Ultimately, our findings highlight the importance of larval habitat quality to future recruitment success.