Variations in abundance of walleyes, Stizostedion vitreum vitreum (Mitchell), in Cedar and Moose Lakes, Manitoba

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Derksen, A. J.
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During the summers of 1962 to 1964, experimental gill netting was conducted in Cedar and Moose Lakes, Manitoba. The age structure of walleyes caught in 9.5 and 10.8 cm experimental nets was examined to determine relative strengths of year classes in both populations. Age compositions of additional samples from the commercial fisheries on both lakes were also examined. Year classes were ranked in order of relative frequency of occurrence in the experimental catches. Estimates of year class strength for each population were correlated with annual fluctuations in walleye catches of the commercial fisheries six years after hatching. Strengths of year classes in Cedar and Moose Lakes were positively correlated with spring discharges from the Saskatchewan River during the first year of life of the year classes. This relationship was best for Cedar Lake walleyes in June and for Moose Lake walleyes in April. The manner in which high discharges may have promoted the success of walleye year classes is discussed. The future abundance of Cedar and Moose Lakes walleyes might be predicted on the basis of observations of spring discharges from the Saskatchewan River. Such information would permit effective management of the commercial walleye fisheries on these lakes.