Kentucky Fish and Wildlife biologists identify genetic markers linked to enhanced size potential in native largemouth bass

​FRANKFORT, Ky. (March 19, 2026) — Kentucky Department of Fish and Wildlife Resources researchers have found the genetic keys to unlocking the potential for bigger largemouth bass, the most popular species sought by anglers.

Biologists with the Kentucky Fish and Wildlife Fisheries Division, collaborating with the Center for Aquaculture Technologies, have identified specific genetic markers associated with enhanced size in native largemouth bass.

The discovery was made through the Fisheries Division’s Thoroughbred Bass Program, which has a research goal of selectively breeding Kentucky-origin bass that carry these markers in order to stock public waters in the future with fish that have a higher probability of reaching trophy size.

“For more than 50 years, biologists have been trying to increase the size potential of largemouth bass,” said Adam Martin, Fisheries Division biologist with Kentucky Fish and Wildlife. “In many states to our south, that effort involves stocking non-native Florida bass or first generation (F1) hybrids. Stocking Florida bass has increased bass size in many lakes in warmer climates but despite other attempts, it hasn’t worked so far in areas colder than southern Tennessee. More northern states like ours haven’t had any great options for improving their genetics until now.”

Martin said this marks a major advancement in fisheries science and management.

“Modern genetic tools are opening up a whole new world of potential that biologists even 10 years ago could only dream about,” he said. “To the best of our knowledge, this is the first time such markers have been identified in largemouth bass.”

In a process known as a Genome Wide Association Study, researchers used whole-genome sequencing to identify single genetic markers linked to large size potential. Fisheries biologists clipped fins from 300 largemouth bass statewide to use for genetic testing. The sampled fish included 150 bass weighing more than 5 pounds from 30 different lakes and 150 slow-growing bass under 3.5 pounds from the same lakes. All samples were confirmed as pure largemouth bass before undergoing full genome sequencing. Researchers then analyzed more than 3 million markers per fish to identify the genetic markers common in trophy fish but rare in smaller individuals.

Because of this recent discovery, department staff can screen potential largemouth bass broodfish for genetic purity and use fish with the best complement of trophy genetics. Then, they will selectively breed fish in department hatcheries to maximize the size potential of the offspring. As selectively bred fish reproduce with wild bass in stocked waters, the desirable growth genetics can integrate into wild populations over time, creating sustained, generational improvement. Kentucky Fish and Wildlife plans to stock public waters with fish having greater trophy-size potential under the name of “Thoroughbred Bass.”

“This process is very similar to the traditional selective breeding programs used in agriculture for millennia,” said Jeff Ross, Fisheries Division assistant director. “The only difference is that we are using genetic markers to pick which fish to breed. Most importantly, we can use bass caught right here in Kentucky - which preserves local adaptation and genetic integrity.”

“The Thoroughbred Bass Program represents a science-driven, sustainable investment in Kentucky’s bass fisheries,” Fisheries Division Director Dave Dreves said. “By combining advanced genetics with traditional hatchery practices, we are working to ensure that future generations of anglers have the opportunity to continue to catch exceptional bass in Kentucky waters.”

Another advantage of this program: research suggests angling pressure can impact fish genetics by removing larger or more aggressive bass. The Thoroughbred Bass Program could help invigorate waterbodies by introducing more replacement fish with genetics for larger size.

“Although the first production of ‘Thoroughbred Bass’ was anticipated in 2026, unfortunately we are currently still awaiting the manufacture of the required screening panel of trophy markers,” Martin said. “Bass only spawn once a year so we only get one shot. Unfortunately, it looks like we will miss our window this year to start the selective breeding process.”

Regardless, biologists will spend significant time this spring and summer collecting and testing hundreds of wild largemouth bass to ensure the best possible broodfish will be available for 2027 production. Additional trophy-sized bass from across the state will also be tested to further confirm the validity of each genetic marker and help narrow down which markers are the most important.

More information is available in the Thoroughbred Bass Program Interim Progress Report on the department’s website (fw.ky.gov). The report will be continually updated with the achievement of new milestones in the Thoroughbred Bass Program.​