Size-dependent selective mortality of Lake St. Pierre yellow perch during their first winter

A moratorium on commercial and sport fishing for yellow perch (Perca flavescens) was instituted in Lake Saint-Pierre in 2012 and has been maintained ever since. Despite this measure, the abundance of spawning yellow perch remains low, and the abundance of 1- and 2-year-old yellow perch is lower than in the early 2000s.

In contrast, young-of-the-year yellow perch show no decline in abundance but rather a decreased growth. This finding suggests a high winter mortality of young-of-the-year yellow perch could explain the low abundance of year-old yellow perch.

The project’s main objective is to test the hypothesis of size-dependent selective mortality of yellow perch in their first winter using fish from the 2020 and 2021 cohorts. The specific objectives are to:

1. Compare recent yellow perch growth trajectories with historical growth trajectories (at least 10 years of data);
2. Verify whether the predatory double-crested cormorant (Nannopterum auritum) selects consumed yellow perch of the year according to size; and
3. Define the size corresponding to the survival threshold of yellow perch in their first winter.

This project is being undertaken in collaboration with Émilie Paquin and Philippe Brodeur of the Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs.