An experiment stocking only female bass is an expensive but tremendous success
A common goal in contemporary fishery management is providing anglers the opportunity to catch trophy largemouth bass.
A common problem in small-impoundment management in southern states is bass crowding: an overabundance of small, slow-growing largemouth bass. Stocking only female bass sounds like a strategy to provide both trophy bass and reduce bass crowding. But does it work?
The pilot project
Tim Bonvechio and Joseph Rydell, fisheries biologists with the Georgia Department of Natural Resources, tested all-female bass stocking in the Ocmulgee Public Fishing Area. Ocmulgee, like other PFAs in Georgia, is intensively managed to provide high fish production, but in this case, the biologists wanted to try to produce trophy largemouth bass sought by area anglers.
The new, 106-acre reservoir was stocked with five female first-generation hybrid northern X Florida largemouth bass per acre in 2005 and 2006. Bluegill, redear sunfish, channel catfish, golden shiners, threadfin shad and lake chubsuckers were stocked as sport and forage fish.
Bass were sampled by volunteer anglers and electrofishing. Growth of the bass was fast; almost all had grown to 18 inches by age 3 and 20 inches by age 4.
Male largemouth bass were first collected in electrofishing samples in 2009, and there was evidence of bass reproduction when the lake was drained in 2012. Some of the male bass may have originated from a small pond within the Ocmulgee PFA drainage, but at least a few of the male bass were individuals that were mistakenly identified as females at the time of stocking.
The experiment produced the trophy bass anglers desired. It took anglers 3.76 hours to catch a bass weighing more than 5 pounds, 7.35 hours to catch a bass heavier than 8 pounds, and 53.25 hours to catch a bass of 10 pounds or better. One 13.25-pound bass was captured by electrofishing.
Success didn’t come cheap. The purchase of hybrid bass fingerlings from a private hatchery was a relatively small cost. The bass then had to be reared to 10 inches so they could be reliably sexed and have high survival after stocking. This required almost a year of personnel time and the use of hatchery ponds to rear the bass and the forage fish needed by the bass to grow to 10 inches. Then, only about half the fish were females usable for stocking into Ocmulgee — the males were stocked elsewhere.
Was it worth it?
Bonvechio and GDNR must think so, because they are repeating the effort. The lake basin remained dry from 2012 until it was refilled in 2016. Forage fish were stocked, followed by bass, but this time, the lake was stocked with all-female progeny of native Georgia largemouth bass that have 70% to 100% Florida bass genetics.
So far, the results have been outstanding. Recaptured bass have grown to more than 8 pounds in 3 years, 11 pounds in 4 or 5 years, and one 4-year-old fish pulled the scale to 13 pounds. Bonvechio has detected a small amount of bass reproduction.
The almost-unbelievable results are a consequence of stocking all-female bass with a high level of Florida bass genetics. Biologists know that only the female Florida bass grows larger than 20 inches and 5 pounds, but Bonvechio suggested other factors also are likely in play. For starters, the bass were stocked into a newly filled lake, and a lot of terrestrial and lowland vegetation was flooded when the lake refilled. This vegetation provided fish habitat, nutrients and a lot of food for invertebrates that, in turn, are food of fishes that feed bass.
The stocked forage fish were rapidly expanding their populations into their new and empty home, so the female bass had plenty to eat. As in 2004, the forage stocked included lake chubsuckers, a native fish found to be a preferred forage of trophy Florida bass in Florida lakes and a fish that should benefit from the flooded terrestrial vegetation.
Management challenges lie ahead. If the limited bass reproduction persists, which is the desired outcome, additional female bass with Florida bass genetics will need to be stocked. Considering the cost of these fish and that only the female bass have trophy potential, catch-and-release is essential to sustain the trophy fishery.
This finite bass population also offers a perfect chance to evaluate changes in catchability of trophy bass over time and with continued fishing effort.
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