Florida bass stocking

Recent studies have shown that the catchability of largemouth bass is not affected by hybridization with Florida bass.

Super strain doesn’t affect native bass catchability

Solid scientific evidence supports the growth of Florida-strain bass to larger sizes than largemouth bass. 

Rumor has it that they are harder to catch than largemouth bass. More on that later, but if correct, could Florida bass stocking efforts create populations of bass that are more difficult to catch?

An average of 15 million Florida bass are stocked annually in southern states. The state of Florida stocks about 1.9 million per year to maintain genetic purity in its waters, but in other states, Florida bass are stocked to provide anglers greater opportunities to catch trophy bass. Texas annually stocks 7.7 million Florida bass fingerlings. Mississippi stocked 500,000 this year to increase trophy bass potential in selected waters.

A natural consequence of stocking Florida bass is that they hybridize with native largemouth bass. The first-generation hybrids of Florida bass and largemouth bass also have greater growth potential than largemouth bass. Twenty years ago, conservation geneticists forewarned of disastrous effects of mixing genes between introduced Florida bass and native largemouth bass. No negative effects have yet occurred.

Solid science has demonstrated that catchability is a genetic trait and is heritable. Several early studies, but not all, found that Florida bass were harder to catch than largemouths. If this is the case, and catchability is heritable, stocking Florida bass into a largemouth population could reduce catchability. The early catchability studies were conducted in small research ponds. Recent studies in Texas and Tennessee evaluated the effect of Florida bass stocking on black bass catchability in large reservoirs.

Pure-strain Florida bass like this fish caught in Orange Lake, Fla., are more difficult to catch than largemouth bass. (Photo courtesy Brian Dolski)

Texas study

Texas Parks and Wildlife Department biologists compared the catchability of Florida bass and largemouth bass in five reservoirs. The genetics of bass captured by anglers were compared with those captured reservoir-wide by electrofishing and assumed to be a random sample of bass in each population.

In two reservoirs, the proportions of angler catch of bass with 95% or greater Florida bass genes were lower than the proportion of bass with 95% or greater Florida bass genes in the populations. In other words, bass with a very high influence of Florida bass genes were less catchable. The proportions of bass with less than 95% Florida bass genes was the same or greater in the angler catch than the electrofishing catch. Florida bass genes had little effect on the catchability of bass with less than 95% Florida bass influence.

Catchability of bass in the other three reservoirs, which had very few bass with 95% or greater Florida bass genes, did not differ across a range of percentages of Florida bass genes.

Tennessee study

Fishery researchers at the Tennessee Cooperative Fishery Research Unit at Tennessee Tech used a similar approach — comparison of the genetics of angler-caught and electrofishing-collected bass — to assess the effect of Florida bass genes on catchability of bass in Chickamauga Lake. They found no significant differences in the proportions of angler catch and electrofishing catch across genealogical classes of first- and second-generation Florida bass X largemouth bass hybrids or back crosses of hybrids with either their Florida or largemouth bass parents. Too few pure Florida bass were captured by anglers or electrofishing to allow meaningful assessment of the catchability of pure Florida bass.

Management implications

Several early studies comparing the catchability of Florida bass and largemouth bass found Florida bass more difficult to catch, but a couple studies found no difference in catchability. Techniques to assess the genetic purity of Florida bass and largemouth bass have advanced greatly in the last 20 years, and it is possible that the discrepant results of these early studies were a consequence of comparing bass of unknown genetic purity.

Rigorous genetic testing with advanced techniques allowed the Texas and Tennessee researchers to accurately describe the genetics of the fish captured by anglers and electrofishing. The results from the reservoir studies support the conclusion that pure Florida bass have lower catchability than native largemouths.

The more-important finding, in my opinion, is that the catchability of bass with less than 95% Florida bass genes is little affected. This is significant, because every stocked Florida bass that survives has the potential to hybridize with largemouth bass. Stocking Florida bass has disrupted the genetic integrity of native bass populations. This may have some yet-to-be-determined adverse effects on bass populations, but the results to date demonstrate that stocking Florida bass will produce a few bigger bass without altering the catchability of the native bass populations.

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About Hal Schramm 169 Articles
Hal Schramm is an avid angler and veteran fisheries biologist.

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