Monitoring Fish Response to Habitat Creation Using Acoustic Telemetry

Coastal wetlands provide critical habitat for fishes in the Laurentian Great Lakes but have been greatly diminished by anthropogenic activities. Various restoration efforts are being undertaken yet little information exists on biotic responses to these efforts. Such information is crucial for understanding the effectiveness of restoration activities. Our objectives are to assess the response of key fish species to habitat creation activities in Toronto Harbour, Ontario, and to estimate seasonal habitat preferences, particularly in winter. In year one, our focus was to deploy and test an acoustic telemetry array and to evaluate macro- and mesohabitat selection and large-scale fish movements in the harbour. Acoustic transmitters, including pressure and temperature sensors, were implanted in 17 largemouth bass (Micropterus salmoides), 17 northern pike (Esox lucius) and common carp (Cyprinus carpio) September 2010. These species include top piscivores and a super-abundant invader of key interest to managers. Detection data were retrieved in November 2010, and will be retrieved again in April and June 2011.  Preliminary results showed considerable partitioning of depth among species. Northern pike selected the deepest habitat throughout the fall, followed by common carp, and all three species moved deeper as the season progressed.  Largemouth bass remained primarily in protected embayments, with two individuals moving far from the release location.  Some northern pike also selected embayment habitats, though many were also found in the open waters of the harbour.  Common carp demonstrated the greatest movements, with one third of fish dispersing from the harbour entirely.  Remaining carp selected both embayments and open-water habitat. Results will inform redeployment of the array in summer 2011 to capture real-time, two-dimensional movements and habitat selection of fishes. Transmitters will be implanted in additional fishes, and possibly additional species such as walleye.