Tracking the early stages of an invasion with biotelemetry: behaviour of round goby (Neogobius melanostomus) in Canada’s historic Rideau Canal

The round goby (Neogobius melanostomus), native to the Black and Caspian Seas, is one of the most wide-ranging invasive fishes, having established in much of Europe and North America. In 2019, round goby were discovered to have colonized a central portion of the Rideau Canal, a 202 km historic waterway in Ontario, Canada. Round goby were found in low densities and had not been previously reported in any adjacent sections of the waterway, implying a newly-established source population. Passage through locks is the most likely means by which round goby can naturally disperse throughout the system, so modifying lock operations and infrastructure to minimize passages could reduce their spread. Additionally, understanding the range expansion and habitat preferences of pioneering individuals can help inform control efforts. We combined acoustic telemetry with hydraulic data to (1) characterize sex- and size-specific movements, (2) identify entry and exit pathways through a lock, and 3) assess dispersal rates and probability. We tracked 45 adult round goby downstream of Edmonds Lockstation during the navigation season from July to October, during which nine were detected inside the lock, with one fish successfully passing upstream. Most fish remained near the release site, though 26% of tagged individuals dispersed. The farthest distance a fish moved was 500 m (downstream) after 27 days, generating a maximum dispersal rate of 18.5 m/day. Although we lacked sufficient statistical power to detect size- or sex-specific movements, males were more commonly detected further from the release site. Our results suggest possible modifications to lock operations and infrastructure that managers could consider to reduce round goby expansion upstream from the invasion site.