Population Connectivity of Larval Yellow Perch in the St. Lawrence River (Canada)

In 2011, an ichthyoplankton survey was conducted along 300 km in the freshwater section of the St. Lawrence River to identify source habitats of larval yellow perch Perca flavescens and to describe their dispersal. At each sampling station, water was characterized (conductivity, dissolved oxygen, turbidity and temperature) to group the larvae originating from the same water mass. Given that young larvae are nearby spawning sites, we considered larvae with a total length <8 mm as representative of the source. Larger individuals (TL 8-28 mm) were used to represent the sites where the larvae have dispersed. Thus, dispersal was quantified by comparing the natal origin with the site of capture. Connectivity between the sources and dispersion habitats was assessed by comparing the elemental composition of otolith cores using LA-ICP-MS. At hatching (source habitats), elemental concentrations of Magnesium, Zinc, Manganese, Barium and Strontium varied significantly among habitats. The quadratic discriminant function analysis used to reclassify larvae obtained a success of 80%. Preliminary results indicate that otolith chemistry is useful in distinguishing the origin of yellow perch production even at a small-scale (< 10 km) and represents a promising tool to quantify dispersal and connectivity of fish larvae exploiting an energetic fluvial landscape.