WINDS AND THE DEMIC STRUCTURE OF A POPULATION OF YELLOW PERCH (PERCA-FLAVESCENS)

Variations in year-class strengths of populations of fish are often attributed to environmental effects such as wind or temperature. Previously, we have presented evidence showing that the yellow perch (Perca flavescens) in a lake are composed of demes or subpopulations that vary independently. Here, we explore the relationship between winds from different directions and the independent variations of the demes of yellow perch in the study lake. We present a model that includes an instantaneous rate of mortality due to winds during the embryonic stage of yellow perch. The variables used to explain the observed egg-mass counts and thus the variations in the size of the demes are lagged egg-mass counts and winds, each of which varies yearly. Using wind and egg-mass census data, we were able to find statistically significant models that explain much of the variation (52-61%) in the independently varying demes (four of six investigated) of yellow perch in our study lake. We also present data that show that water temperatures vary in different ways at different sites in the same year, and in different ways at the same site in different years.