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A community-level approach to assessing fish movements and habitat restoration in Toronto Harbour
Nicolas W. R. Lapointe1, Steven J. Cooke1, Susan E. Doka2
1Department of Biology, Carleton University, 1125 Colonel By Dr., Ottawa, ON, K1S 5B6, Canada
2 Fisheries and Oceans Canada, 867 Lakeshore Rd., Burlington, Ontario, L7R 4A6, Canada
3 Fisheries and Oceans Canada, 867 Lakeshore Rd., Burlington, Ontario, L7R 4A6, Canada
When studying animals using electronic tags, care must be taken to minimize tagging effects on experimental subject behaviour. For fish, researchers often focus on effects of tag weight relative to fish weight; however, tag volume may also affect behaviour. Where tag volume is large relative to fish size, potential effects include impeding feeding by restricting gut expansion, reducing swimming performance, and pressure narcosis of tissues surrounding the tag. To evaluate these effects, we implanted small (120-150 mm) Pumpkinseed (Lepomis gibbosus) with two sizes of dummy tags (approximating Vemco V5 and V7 transmitters). Measures of tagging effects included short-term survival, surgical wound healing, swimming performance (time to exhaustion), and final gut-content volume. Mortality rates were high, likely because of complications with holding wild fish in captivity, but did not differ among treatment groups. Healing rates were high for all treatments, and were not demonstrably associated with tag presence or size. Swim-trial performance was only related to fish size for theV5 group, and was not affected by tagging. Gut-content volume did not differ among treatments. Results indicate that both transmitter sizes can feasibly be implanted in small Pumpkinseed (and other fishes with similar morphology) without major behavioural effects.
A total of 14 V13 acoustic transmitters were implanted in Brown Bullhead, and an additional 10 V9 acoustic transmitters were implanted in Yellow Perch. Attempts to tag Brown Bullhead resulted in limited success; three of the fourteen fish were never detected, and only two appeared to remain alive and active in the harbour after one year. The remainder died, shed their tags, or were harvested; however, their ultimate fate remains unknown. No Brown Bullhead were detected emigrating from the harbour. Surviving Brown Bullhead had relatively restricted home ranges, remaining either entirely within the Toronto Islands area or the larger Inner Harbour, but never exiting the harbour or traveling to the Outer Harbour. Greater success was achieved in tagging Yellow Perch; at least four survived from Fall 2012 to Spring 2013, and three others may also be alive with working transmitters but have maintained a restricted home range in the spring. Continued monitoring over the summer will reveal whether these individuals continue to move actively. Yellow Perch generally showed similar large-scale habitat preferences, moving throughout the Outer Harbour in early fall, then travelling to the Inner Harbour in late fall and to the Toronto Islands area for the majority of the winter (February and March). In spring, they returned from the Toronto Islands area to the open waters of the Inner Harbour.