Relative abundance and biomass, age, and growth of yellow perch, Perca flavescens (Mitchill), in four adjacent man-made lakes in southern Manitoba

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Ratynski, Raymond A.
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Characteristics of populations of yellow perch, Perca flavescens (Mitchill), in four adjacent man-made lakes in southern Manitoba were examined during the open water periods of 1978 and 1979. Studies of the physical and chemical regimes of the Fort Whyte lakes during 1977-1978 indicated greatest eutrophy in Lakes I and II and lowest in Lakes III and IV. Relative perch abundance and biomass values in 1979 were highest in Lake I but were similar for Lakes II, III, and IV. Dissimilarity of recruitment of the 1977 and 1978 year classes between Lake I and the other three lakes is attributed to intraspecific predation of young perch by numerous adult perch in Lake I. Older perch dominated the catch in Lake I while the newly recruited one-year-olds formed 9% of the population in 1978 and 3% in 1979. In the other lakes there were fewer old perch. In 1978, age 1 perch made up 33%, 44% and 26% of the population in Lake II, III, and IV respectively. In 1979, they represented 65% of the population in Lake II, 64% in Lake III, and 69% in Lake IV. Among Lakes II, III, and IV, mean length of perch at time of annulus formation in 1978 was highest in Lake II and lowest in Lake IV for all ages. In comparison to the other lakes, yellow perch in Lake I had the highest mean length for ages less than 3 but the lowest mean length for ages greater than 3. These differences were not great in magnitude. At the time of annulus formation in 1979, there were no significant differences in mean lengths at each age. In comparison to other North American waters, growth of perch at Fort Whyte was slow. The major response of the perch population in Lake I to greater eutrophy was to increase its biomass but this was by increasing population size rather than by increasing growth. The perch population of Lake II failed to respond similarly perhaps because nutrient input to the lake is sporadic and sustained loading is required for increased productivity. A greater magnitude of difference in perch biomass than in perch abundance between Lake I and Lakes II, III, and IV is attributed to higher incidence of older, larger fish in Lake I.