The distribution and habitat associations of stocked American Eel, Anguilla rostrata, in Lake Ontario and the Upper St. Lawrence River

From 2010 to 2011, I characterized nearshore patterns of stocked American Eel (Anguilla rostrata) abundance and size and identified habitat associations in the eastern portion of Lake Ontario, the Upper St. Lawrence River, and two Lake Ontario tributaries; the Moira and Napanee rivers. The locations represent two contrasting spatial scales and environments; 1) large lake and river habitats, and 2) small-to-medium sized stream habitats. The study was conducted using transect boat electrofishing and point sampling with a backpack electrofisher. Habitat parameters collected at each sampling area included water chemistry, vegetation density and substrate composition. Generalized additive models (GAMs) were used to assess which habitat parameters most explained eel occurrence, and canonical correspondence analysis was used to determine if habitat associations were related to eel length. Overall, my research demonstrated that eels have specific habitat preferences, but that those preferences change as eels grow. The habitat available for stocked eels to use to grow and mature in Lake Ontario tributaries is limited by barriers. Eel densities are high in both waterbody types and this could have detrimental impacts to the goals of a future stocking program, such as density-dependent mortality or male-biased sex ratios. Monitoring should continue to determine the long term effectiveness of the stocking program.