When a bass tournament ends and fish are released at the weigh-in site, what happens next?
That question drove a biotelemetry study on Rideau Lake — the same lake system that hosts dozens of competitive bass tournaments each season — conducted by Ontario Ministry of Natural Resources researcher Mark Ridgway in the late 1990s, and funded in part by the Rideau Lake Environmental Foundation.
The Experiment
In the third week of June 1997, 27 largemouth bass from a variety of locations in Rideau Lake were captured by volunteer anglers, surgically implanted with radio tags, and displaced to predetermined locations. Displacement distances ranged from 1.5 to 16.5 km — a realistic range for a tournament on a lake that stretches 35 km. Fish were tracked multiple times per week through the fall using radio and ultrasonic telemetry.
Most Fish Don’t Go Home
Overall, 37 percent of displaced largemouth bass returned to their capture site. All fish that returned were displaced within 8 km of their capture site. Three of the seven fish that did return didn’t make it back until the following spring. Fish displaced more than 8 km showed no return at all.
It took approximately two weeks for displaced bass to move more than 400 m from the release site. The fish weren’t bolting for home — they were moving slowly and, in many cases, settling into a new home range rather than retracing their route.
One finding that might seem counterintuitive: despite the low fidelity to original home ranges once displaced, home ranges of displaced and control fish were similar in size. Displaced fish weren’t wandering aimlessly — they were establishing ranges of comparable size in unfamiliar territory.
Survival Over the Season
The overall survival estimate for the fishing season was 0.587, with the two lowest survival periods occurring at the start of the fishing season and around the Labour Day weekend — times when one might expect brief increases in fishing effort.
Comparing these results to trapnet data from 1981, the upward shift in survival estimates for 1997 relative to 1981 suggests that survival may be higher now than in the past — a trend the author attributes in part to the growing prevalence of catch-and-release practices and improved handling procedures.
The Caveats
Ridgway is careful about the limits of what this study can tell us. This study displaced single fish and not large groups of bass that normally occur in most post-tournament releases. In the latter case, many fish are typically released in relatively few locations, so post-release movements away from these sites may differ from what was observed. The study also took place in a northern lake where comparatively cool water temperatures are known to support better survival outcomes.
What It Means
The picture that emerges is nuanced. Largemouth bass are not particularly good at finding their way back after tournament displacement — most simply don’t. At the same time, survival through the fishing season, at least under the conditions studied here, was reasonable. The bigger unresolved question, as Ridgway frames it, is what happens when large groups of displaced fish are released repeatedly at the same sites over the course of a season — a scenario this study was not designed to capture.
Financial support for this research was provided by the Big Rideau Lake Association, the Rideau Lakes Environmental Foundation, the Ontario Federation of Anglers and Hunters, and the Ontario Ministry of Natural Resources, in an early example of community-supported fisheries science on a lake that has continued to be the subject of research ever since.
Ridgway MS. 2002. Movements, home range, and survival estimation of largemouth bass following displacement. American Fisheries Society Symposium 31:525–533. Download the PDF.