Comparison of the yellow perch, Perca flavescens Mitchell, populations in Henderson Lake and Savanne Lake, Ontario / Beverlee J. Ritchie. --

Yellow perch (Perca flavescens) in Henderson Lake exhibit
\nstunted growth and poor condition at all ages. In addition, they have
\nlower fecundity, longer life span, slower maturation rate, and greater
\nsurvival compared to perch in Savanne Lake.
\nGillnet catch-per-unit-effort (CPUE) indicated that abundance of
\nrecruited perch was comparable between lakes, but that fish are at least
\n5 years of age before they are recruited to this gear in Henderson Lake.
\nGillnet CPUE identified diurnal activity periods for perch and walleye
\n(Stizostedion vitreum vitreum) in both lakes, but the evening
\noffshore 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.
\nNo relationship between spring water temperature or precipitation
\nand year-class strength of Savanne young-of-the-year (YOY) walleye and
\nperch year-classes could be demonstrated. Strong YOY walleye
\nyear-classes did not occur in the same years as strong YOY perch
\nyear-classes in Savanne Lake. However, weaker YOY walleye year-classes
\nwere produced in those years when YOY perch grew faster.
\nSeasonal and annual changes in forage abundance determined the
\nfrequency of prey items found in Savanne and Henderson perch stomachs. 
\nIntraspecific diet overlap and cannibalism was greater in Henderson perch than in Savanne perch. The incidence of cannibalism was a function
\nof the availability of alternate prey in both lakes. Predation by
\nwalleye, northern pike (Esox lucius). and perch on same prey
\n(ninespine sticklebacks Pungitius pungitius, perch, and mayfly
\nnymphs) is frequent in Henderson Lake, but interspecific segregation of
\nprey utilization occurs in Savanne Lake.
\nValues for mean age to maturity of male and female perch as
\ndetermined by the proposed Probit Method were more comparable to
\nempirical values than those determined by the Abrosov, Modified Abrosov,
\nand Lysack methods.
\nApparent differences between the two populations in behavior and
\nbiological characteristics are attributed to; lower predation levels on
\nHenderson perch; differences in the physical structure of the two lakes.
\nMutual predation on the forage base in Henderson Lake at both an
\nintraspecific and interspecific level helps to amplify these
\ndifferences. The effect of physical characteristics, especially water
\ntransparency and macrophyte growth on predator-prey interactions is also
\nexamined.

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