Evaluating Effects of Dreissenid-Induced Water Clarity Changes on Walleye Production

Published accounts of some Ontario walleye populations show declines following dreissenid (zebra and quagga mussel) invasion coincident with increases in water clarity. A survey of 62 North American lakes showed that Secchi depth in dreissenid invaded systems increased in 79% of analyzed cases. A published walleye production model generated for Ontario lakes explicitly models the production of this species on the basis of light-sensitivity; as water clarity increases, optimal walleye habitat area decreases. Lakes in Manitoba are dominated by walleye which make up 70% of commercial harvest value, but it is unknown whether these lakes are accurately described by the Ontario model. With the recent discovery of zebra mussels in Lake Winnipeg, there is concern surrounding the impact of this invasion on the walleye fishery it supports. In this study, we will evaluate the application of the Ontario walleye production model to lakes in Manitoba, with the ultimate goal of predicting changes in walleye production from Manitoba lakes as a result of zebra mussel establishment. This approach will provide an example of tools available to resource managers so as to anticipate the potential impact of invasive dreissenids on economically valuable walleye fisheries and consider these impacts in their management strategies.