Trophic effects of macrophyte removal on fish populations in a boreal lake

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Rabasco, Robert
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Northern pike ('Esox lucius'), yellow perch ('Perca flavescens'), and pumpkinseed ('Lepomis gibossus ') rely on vegetated littoral zones as spawning substrate, foraging areas, and refuge from predation. However, the removal of littoral zone habitat has increased in the past twenty-five years. This led Department of Fisheries and Oceans Canada (DFO) researchers to study the effects of habitat loss on northern pike production in Lake 191 in the Experimental Lakes area (ELA) in northwestern Ontario. The removal of 50% of littoral zone macrophytes led to a 50% reduction of northern pike abundance, increases in yellow perch and pumpkinseed abundance, and changes in the size structure and biomass of the zooplankton community. The present study was initiated to help determine underlying causes for changes in the fish and zooplankton community in Lake 191. Fish from Lake 191 were examined for feeding patterns. The policies of Manitoba, Ontario, Minnesota, Wisconsin, and Michigan for the control and/or removal of aquatic macrophytes were reviewed. (Abstract shortened by UMI.)