Assessing the Interdependence of Assemblages from Rainy Lake Fisheries Data

Abstract

We applied ad hoc methods to quantify differences among fish communities in four different locations in Rainy Lake using data from index netting from long-term studies. Our analysis addressed problems of inconsistencies in data collection. We established the amount of differences and similarities among the communities by analyzing species diversity over time, utilizing matrices of partial correlations and discriminant function analysis. We also identified role reversal, i.e. synchronization in fluctuations of relative catch-per-unit-effort (CUE) between pairs of species in these communities. In the less disturbed communities, walleye (Stizostedion vitreum) contributed most to the synchronization in the fluctuations of the yearly relative CUE among six common species. In the more disturbed locations, this contribution was primarily due to yellow perch (Perca flavescens) and sauger (Stizostedion canadense). The disturbed community in one location (the North Arm) exhibited marked decrease in species diversity. Recent restrictions on the fisheries in the North Arm resulted in an increase in species diversity. Fish communities, particularly in large lakes, may differ in the detail of species interactions and population fluctuations among locations within the lake. These differences must be taken into account in analysis and management of fisheries.