Seasonal Movement and Habitat Selection of Fishes in the Toronto Harbour

Due to extensive degradation of fish and wildlife habitats and associated population declines, Toronto Harbour was designated as one of the Great Lakes areas of concern in 1977. While significant efforts have been dedicated to restoring fish habitat along the Toronto waterfront and at the Toronto Islands, little is known about their effectiveness. Success of restoration efforts depends on an understanding of fish habitat requirements across the entire year, along with needs for connectivity among habitats. Despite our knowledge of fish habitat requirements during spawning and the summer, overwintering habitat requirements have remained largely unknown due to challenges of winter sampling. To better identify habitat selection of fish species within the Toronto Harbour and its coastal embayments, adult largemouth bass, northern pike, walleye, and common carp were tracked across multiple seasons using acoustic telemetry.  Specifically, we monitored fish movements across seasons in relation to existing habitats and tested whether overwintering habitats were different from those used during spawning and summer periods. Results indicate that almost all largemouth bass and northern pike remained resident within the Toronto Harbour throughout the year, while almost 6% of common carp left the harbour. Moreover, resident northern pike and common carp were relatively active across seasons, whereas resident largemouth bass were reasonably quiescent during the coldest period in the year.