Comparison of the yellow perch, Perca flavescens Mitchell, populations in Henderson Lake and Savanne Lake, Ontario / Beverlee J. Ritchie. --
Ritchie, Beverlee J.
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Yellow perch (Perca flavescens) in Henderson Lake exhibit stunted growth and poor condition at all ages. In addition, they have lower fecundity, longer life span, slower maturation rate, and greater survival compared to perch in Savanne Lake. Gillnet catch-per-unit-effort (CPUE) indicated that abundance of recruited perch was comparable between lakes, but that fish are at least 5 years of age before they are recruited to this gear in Henderson Lake. Gillnet CPUE identified diurnal activity periods for perch and walleye (Stizostedion vitreum vitreum) in both lakes, but the evening offshore movements and morning onshore movements by perch in Henderson Lake were more pronounced and prolonged. Sampling in littoral areas with bag seines prove that perch and walleye closely associate at dawn and dusk in Savanne Lake, but do not associate at any time in Henderson Lake. Young perch are the dominant littoral species in Savanne Lake, but share dominance with unutilized mimic shiners (Notropis volucellus) and blacknose shiners (Notropis heterolepis) in Henderson Lake. No relationship between spring water temperature or precipitation and year-class strength of Savanne young-of-the-year (YOY) walleye and perch year-classes could be demonstrated. Strong YOY walleye year-classes did not occur in the same years as strong YOY perch year-classes in Savanne Lake. However, weaker YOY walleye year-classes were produced in those years when YOY perch grew faster. Seasonal and annual changes in forage abundance determined the frequency of prey items found in Savanne and Henderson perch stomachs. Intraspecific diet overlap and cannibalism was greater in Henderson perch than in Savanne perch. The incidence of cannibalism was a function of the availability of alternate prey in both lakes. Predation by walleye, northern pike (Esox lucius). and perch on same prey (ninespine sticklebacks Pungitius pungitius, perch, and mayfly nymphs) is frequent in Henderson Lake, but interspecific segregation of prey utilization occurs in Savanne Lake. Values for mean age to maturity of male and female perch as determined by the proposed Probit Method were more comparable to empirical values than those determined by the Abrosov, Modified Abrosov, and Lysack methods. Apparent differences between the two populations in behavior and biological characteristics are attributed to; lower predation levels on Henderson perch; differences in the physical structure of the two lakes. Mutual predation on the forage base in Henderson Lake at both an intraspecific and interspecific level helps to amplify these differences. The effect of physical characteristics, especially water transparency and macrophyte growth on predator-prey interactions is also examined.