Too much of a good thing

Healthy bass populations produce quality bass.

Does catch-and-release keep fisheries from regulation benefits?

The adoption of catch-and-release benefited black bass fisheries, but now many fisheries managers wish it would go away — or that at least a few anglers would harvest some bass.

What’s up with this seemingly counterproductive thinking?

Bass fishing and management of bass fisheries changed drastically in the late 1970s and early 1980s. Before, management focused on maintaining high numbers of bass. For that reason, most fisheries had a creel limit and sometimes a minimum size limit.

Whether the stimulus was tournaments in which the total weight of a limit determined success, declining catches in aging reservoirs, or just a reorientation of anglers toward higher-quality fish, anglers wanted larger bass.

Fisheries managers responded with regulations designed to restructure populations to hold a greater number of large fish. Enter the slot limit. The concept behind a slot limit (technically, a protected slot limit) is to, via angler harvest, reduce the number of bass below some intermediate size to provide more food for intermediate-size bass and stimulate faster growth to larger sizes.

Initially, slot limits worked. But as the catch-and-release ethic gained popularity, well-meaning anglers released all bass, not just those protected by the slot. With recruitment high and harvest mortality low, the number of fish in a population increases. At some point, they begin competing for forage, growth slows and production of large bass diminishes.

Giants like this is what most bass anglers want to catch.

This is the situation that some fishery managers think afflicts many bass fisheries today, but the hypothesis hasn’t been tested. Recent research by fisheries scientists at Mississippi State University supports the contention that a catch-and-release addiction may trump potential benefits to be realized by selective harvest.

The MSU team analyzed changes in largemouth bass abundance, size structure and angler catch in Ross Barnett Reservoir from 1989 to 2015. Three regulations were used during this time period: a 13- to 16-inch slot limit from 1989 to 1997, a 15-inch minimum length limit from 1998 to 2008, and a 12-inch minimum length limit from 2009 to 2015.

The average size of bass greater than 12 inches decreased over time, suggesting the 12-inch and 15-inch minimum length limits led to, on average, smaller bass. However, the size of the largest bass in the population increased with the minimum length limits, as did the proportions of bass population larger than 12 inches.

Angler catch rate increased throughout the period when the 13- to 16-inch slot was in effect and remained high during the 15-inch and 12-inch minimum-length limit periods.

Healthy bass populations produce quality bass.

The most dramatic change was the live-release rate, which increased from 35 percent in 1989 to 98 percent in 1998 and remained above 80 percent from 1999 to 2015. In other words, the live-release ethic spread among anglers at the same time as the 13- to 16-inch slot was in effect and has changed little since.

Do bass regulations affect bass populations? Not at Ross Barnett. The only notable change in population size structure occurred between 1989 and 1998, coincident with the 13- to 16-inch slot but also coincident with the upsurge in catch-and- release. The angler catch rate increased sharply from 1989 to 1998 but stayed level and was not affected by the change to a 15-inch or 12-inch minimum length limit.

Is catch-and-release affecting bass populations. Apparently so. The top 10 percent of the population is a little bigger, and the proportions of fish larger than 12 inches has increased — exactly the changes one might expect from high rates of live release. This is good, but the average size above 12 inches has declined, suggesting growth may be slowing as a result of stockpiling of smaller bass, just as biologists have suspected.

Appropriate harvest by anglers is an essential component of maintaining quality bass fishing. On productive bass waters such as Ross Barnett, harvest of smaller, keeper bass will likely improve the quality of fish you catch.

About Hal Schramm 182 Articles
Hal Schramm is an avid angler and veteran fisheries biologist.