**The title, authors, and abstract for this completion report are provided below. For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
Bio-physical forcing of walleye recruitment in western Lake Erie
2 Biology Dept., U.
3 Ont. Min. Nat. Resources, Wheatley,
A new model to describe egg deposition and hatching together with a three dimensional model of nutrients, phytoplankton and zooplankton in Lake Erie was used to evaluate the potential of the match-mismatch hypothesis to explain inter-annual variations of walleye recruitment in the west basin of the lake. Both models used the ELCOM (Estuary Lake Computer Model) model, readily available from the Centre for Water Research at the University of Western Australia, to describe the hydrodynamics and transport of organisms. The egg and larvae model used temperature-dependent functions for egg deposition and hatching and was shown to make reasonable predictions of egg and larval abundances. To predict nutrients, phytoplankton and zooplankton, ELCOM was coupled with the ecological model CAEDYM, also from the Centre for Water Research. A sensitivity analysis of CAEDYM, coupled with a 1 dimensional version of ELCOM, was first conducted to better understand the behavior of this complex model and guide its calibration to Lake Erie. The three dimensional model (ELCOM-CAEDYM) was subsequently shown to make reasonable predictions of zooplankton, phytoplankton and nutrients in the main calibration year, 2002. Two major bodies of observational data disagreed on their portrayal of plankton dynamics in the southern portion of the west basin. This and the model results suggested, contrary to prior expectation, that this region of the lake might not be a dependable high quality foraging area for walleye larvae. However, the modeling did suggest that years of high recruitment success were also years in which larval distributions during their critical first feeding period overlapped areas of relatively high zooplankton biomass along the eastern margins of the southern west basin. By contrast, larvae were predicted to remain isolated from areas of high zooplankton biomass in a low recruitment year. Quantitative and objective measures of predicted overlap between larvae and their food (zooplankton) are still underway, but preliminary results appear to show that physically-driven variations in overlap between first-feeding larvae and zooplankton may indeed be important to recruitment of west basin walleye.