**The title, authors, and abstract for this completion report are
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GLFC via e-mail or via telephone
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Bio-physical forcing
of walleye recruitment in western Lake Erie
2 Biology Dept., U.
3 Ont. Min. Nat. Resources, Wheatley,
Abstract
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.