Spatial Ecology of Smallmouth Bass (Micropterus dolomieu) in the St. Lawrence River

Abstract

Smallmouth Bass (Micropterus dolomieu) are an important sportfish in the connected waters of Lake Ontario and the St. Lawrence River and provide large socio-economic benefits. For several reasons, including increasing pressure from competitive angling events, as well as uncertainty about the state of the Smallmouth Bass population arising from provincial and state assessment programs, there is an urgent need for more information about the spatial ecology of this species in these waters. The St. Lawrence River provides a unique opportunity to examine the spatial ecology of this species in habitats without a thermocline. This study used acoustic telemetry with pressure (dBar ≈ depth in m) and temperature sensors to examine the spatial ecology of Smallmouth Bass in the Forty Acre Shoal, which is a section of the St. Lawrence River that contains deep water areas (>20 meters) as well as an abundance of connected shallow (<20 meters) habitat. Smallmouth Bass occupied similar depths as found in previous studies, indicating that factors other than temperature might play an important role in summer depth selection. Home range estimates (95% and 50% Minimum Convex Polygons) were more than double the size of estimates from a nearby study in Lake Ontario. The home ranges of individuals in this study indicate that Smallmouth Bass caught during competitive fishing events are likely displaced well beyond their established home ranges where return rates and long-term effects are currently unknown. Preferred depths and activity rates varied seasonally, with winter characterized by deeper depths and reduced horizontal activity relative to summer. Large movements during winter were also found, providing further evidence that reduced movement and activity during winter may be facultative instead of obligate. This thesis improves our understanding of the spatial ecology of Smallmouth Bass within the St. Lawrence River and provides important considerations for assessing, managing, and conserving the Smallmouth Bass populations in large waterbodies.