Abundance, growth, and life history characteristics of sympatric walleye (Sander vitreus) and sauger (Sander canadensis) in Lake Winnipeg, Manitoba

Walleye (Sander vitreus) and sauger (Sander canadensis) are the two most economically valuable and sought-after species in the Lake Winnipeg fishery, the second largest freshwater commercial fishery in Canada. We compared recent temporal trends (1979-2003) in population and life history characteristics of these species across the three main management zones of the lake (north basin, channel region, and south basin). Walleye abundance (gill net catch-per-unit-effort) increased relative to sauger abundance, particularly in the north and south basins, and the ages and sizes of the sampled fish exhibited greater spatial and temporal variabilities in sauger than in walleye. Walleye of the south basin and channel region exhibit a bimodal growth pattern, previously unreported for walleye populations. Growth rates of both walleye and sauger increased, and ages and sizes of maturity generally decreased from 1979 to 2003. However, walleye showed much greater flexibility in these traits, both spatially and temporally, than sauger. Sauger utilize a reproductive strategy of younger age and smaller size at maturity and higher fecundity with smaller, more lipid-rich eggs relative to walleye. Recent environmental and/or harvesting conditions on the lake appear to favour walleye over sauger, and differences in their life histories could make the sauger population more vulnerable to the impacts of commercial harvest than the walleye population. (c) 2010 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.