Feeding ecology and movement of introduced yellow perch (Perca flavescens) in BC lakes

Yellow perch (Perca flavescens) are a non-native species in most areas of British Columbia (BC) and could impact those ecosystems where they are introduced. To address this, I investigated seasonal diet composition and basic movement of introduced yellow perch in lakes within the Okanagan Region of British Columbia. In addition, a trial of the use of artificial spawning substrates as a potential method of removing eggs was completed. Diet composition was determined during five seasonal sampling periods, by counting and identifying items within perch stomachs. I compared diet composition among lakes, and among seasons and size classes within each lake using a multivariate analysis. Diet composition of yellow perch varied by lake. Most notably, yellow perch diets did not include juvenile fishes in several lakes, but the fish consumed large proportions of zooplankton. It is possible that diet composition of introduced yellow perch could be predicted based on presence or absence of predators and refugia for prey species. Prey selectivity and diet overlap with rainbow trout was also determined. Prey selectivity of perch varied among study lakes and seasons. Significant diet overlap between yellow perch and rainbow trout occurred in one of two lakes tested, likely lake-specific due to variable strains of rainbow trout stocked. Radio telemetry showed that in summer, yellow perch were found relatively close to shore, with no significant difference found among time periods within a 24-hour tracking session. In spring, yellow perch were significantly farther from shore when ice was covering the lake, and moved closer to shore as the ice receded. This coincided with the beginning of the spawning season at temperatures of 3.8 °C, the lowest end of the known spawning temperature range. Trials using artificial spawning substrates were successful. Perch spawned multiple times on all artificial spawning substrates and eggs were removed from the lake in an attempt to reduce spawning success. Overall, yellow perch displayed the expected characteristics of a generalist species across all study lakes, as would be expected in their native range; however, some specialization within specific lakes was observed.