Submerged Aquatic Vegetation and Yellow Perch Population Collapse in Lake St. Pierre (St. Lawrence River): A Thirty-Year Tale of Fish Community Evolution

The yellow perch (Perca flavescens) fishery was of great importance in Lake St. Pierre, the largest fluvial lake of the St. Lawrence River system, until the population collapsed in the mid-1990s. The population has not recovered despite a major reduction in fishing effort, thus a complete moratorium was imposed in 2012. Low recruitment and habitat quality deterioration are among the potential causes preventing the population’s recovery. For instance, submerged aquatic vegetation (SAV) has experienced a reduction since 2007, and this is hypothesized to have led to yellow perch habitat loss and to a change in fish community composition. By using time-series data spanning more than 30 years, we evaluated the influence of SAV abundance and physico-chemical variables on fish community structure. Moreover, we calculated indexes of β-diversity to evaluate community dissimilarity over time. SAV abundance was estimated using satellite imagery while fish data were gathered using a standardized gill and seine netting survey. Preliminary results show a positive association between yellow perch and SAV and a decline in SAV-associated species over time. This is the first study to use a long-term data set to identify the influence of environmental factors on the Lake St. Pierre fish community.