The role of turbulence on the early life history and recruitment of Walleye in Lake Erie

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Understanding the recruitment of commercially and economically important fish species is critical to their management and sustainability in Canada. This is the case for Walleye in Lake Erie, which support an annual multi-billion-dollar fishery for Canada and the USA. Multiple spawning sites exist, each differing in quality and contribution to the production of fish larvae. Uncertainties exist about larval growth/survival during their first 3-4 months when spring water temperature and turbulent water motions affect recruitment. Locating suitable habitat at the correct time (i.e., ideal water temperatures and abundant zooplankton prey) may explain patterns in recruitment (i.e., match/mismatch hypothesis 1: larval transport). Moreover, the effects of near-bed turbulence (i.e., bed shear stress) on egg dislodgement to soft sediments where they suffocate, the fate and transport of eggs and larvae through the water column and lake basin, and the effects of water-column turbulence on larval feeding may be important but are yet unknown. Insights from marine systems indicate that low levels of turbulence enhance feeding by fish larvae by increasing encounters with prey, but high turbulence interferes with capture mechanisms leading to lower prey capture. Walleye larval survival and growth could be reduced by high water column turbulence once they reach their nursery locations causing a second match/mismatch (i.e., match/mismatch hypothesis 2: larval feeding). We propose, therefore, to determine: (i) how Walleye egg hatching /dislodgement and larval growth are affected by turbulence using laboratory experiments and coupled three-dimensional lake hydrodynamic-ecological models, (ii) when/where these turbulence effects occur, (iii) the relative contributions of the various spawning sites, and (iv) how larval fish move from spawning sites to nursery sites using a biophysical particle tracking model (i.e., individual-based model). This biophysical modelling system will be developed to predict the conditions at Walleye spawning and nursery locations in Lake Erie, which is critical to the Ontario Ministry of Natural Resources and Forestry's management of this important fishery, and thus of great benefit to Canada.