Dispersal of tournament-caught bass

These proud anglers caught these bass 35 miles from the tournament weigh-in and release site. Recent science says they will swim back toward their capture site.
These proud anglers caught these bass 35 miles from the tournament weigh-in and release site. Recent science says they will swim back toward their capture site.

Fisheries managers have long been concerned with “stockpiling,” the accumulation of bass near tournament weigh-in and release sites. Multiple studies have assessed the post-release movement of tournament-caught bass. The results have been inconsistent, some studies finding rather rapid dispersal, others finding bass languishing near release sites. A recent Canadian study compared the dispersal of tournament-caught largemouth and smallmouth bass across seasons.

Is stockpiling an issue?

Biologists have been concerned about the continual addition of bass to a small area (the release site) for a couple reasons. First, while the tournaments may be catch and release events, harvest-oriented anglers can exploit the concentrated bass. This is an old and largely outdated argument. The increased adoption of live release reduces this affect. However, tournaments are size selective — the anglers are trying to weigh in the largest fish they can catch. Thus, the bass released from the tournament are larger — sometimes much larger — than the average fish in the population. Even low removal by harvest-oriented anglers could reduce the abundance of larger bass.

A second concern is the depletion of forage fish by the increased density of bass and, in turn, impaired health of hungry bass. Because, as just noted, the released fish tend to be larger bass, this potential problem could become serious. Big bass eat a lot of forage.

Measuring dispersal

The study was conducted in Big Rideau Lake, Ontario. Big Rideau Lake has a large main basin where the fish were caught. Weigh-in and release was at the north end of the lake approximately five miles from the main basin; this five-mile section of the lake is narrow. Tournaments occurred in early June (water temperature 64 to 68 °F), late June (72 to 75 °F), August (75 to 79 °F), and October (54 to 57 °F).

Largemouth (average length 16 to 18 inches among seasons) and smallmouth (average length 16 to 19 inches) were implanted with sonic transmitters prior to their release after weigh in. Fixed receivers monitored the fish’s movement beyond 330 yards from the release site and their return to the main basin where they were caught.

Some fish left the release site immediately. All largemouth had dispersed from the release site in four to forty days among the four tournaments. The more mobile smallmouth left the release site in three to 18 days.

Return to the main basin was much slower. Fifty percent of the largemouth returned to the main basin in 3.6 to 7.8 months; all largemouth returned to the main basin in 18.5 months. Fifty percent of the smallmouth returned to the main basin in 13 days to 3.3 months; all smallmouth returned to the main basin in 20 months. Note that return to the place of capture was not measured.

All bass left the release site and eventually returned to the main basin. The return times differed between species and among seasons. Largemouth from the October tournament returned fastest, those from the August tournament had the slowest return. Most of the smallmouth returned faster than the largemouth, but the October tournament fish were the slowest to return.

Interpretations and implications

Scientific studies have found that both largemouth and smallmouth exhibit homing — the ability to return to a previously occupied area — so their movement back to the main basin where captured is expected.

Good livewell care and releasing healthy fish will help them disperse from release sites.
Good livewell care and releasing healthy fish will help them disperse from release sites.

The wide variation in the return times, which also has been observed among previous studies, doesn’t really surprise me. As every angler knows, bass live where they have good habitat and good forage. They also know that at least some bass follow the forage. The long return times for some of the released fish can be attributed to the displaced, tournament-caught bass finding good habitat and abundant forage along their way home.

The conservation concerns of stockpiling of tournament-caught bass — increased harvest and local forage depletion — may have merit on some waters. But the increased practice of catch and release would reduce harvest of concentrated fish, and the bass’ instinct to move to find forage would minimize the consequences of forage depletion, at least on the bass.

As an angler, I have an additional concern — removal and displacement from the area of capture. My observations on Pickwick Lake support certain areas “turning on.” Tournament anglers are quick to learn where the hot bite is. The fish are caught, transported many miles, and weighed. Most survive and disperse from the release site. But, according to the Big Rideau Lake results, it may take a year or longer for the fish to return to their area of capture. With well over 100 tournaments on Pickwick each year, it is likely that some formerly productive areas become depleted of bass.

Fortunately, part of the fun and challenge of bass fishing is finding the bass.

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