Bass DNA is slowly revealing its secrets through TPWD research.
By Larry D. Hodge
Florida largemouth bass were introduced into Texas waters in 1972. Since then, the state record largemouth bass increased from 13.5 to 18.18 pounds. The northern largemouth bass native to the state seldom reach double-digit size. This was clearly demonstrated by the fact that the first state record of 13.5 pounds stood for 37 years.
Scientific methods for identifying species and subspecies of bass have improved from using meristic (countable) traits to phenotypic (isozyme or amino acid) characteristics to DNA profiles. Research strongly suggests Florida largemouth bass have heritable characteristics that allow them to achieve unusually large size, but early researchers cautioned that only a small fraction of stocked Florida largemouth bass would reach trophy size in Texas.
“When we started our selective breeding program, we felt it was time to use techniques so readily and successfully used in agriculture to produce a new and better strain of largemouth bass for Texas anglers,” says Allen Forshage, director of the Texas Freshwater Fisheries Center in Athens, headquarters for the ShareLunker bass breeding program. “We felt that fish of trophy size had a better chance of producing offspring that might also grow unusually large.”
To achieve that goal, the ShareLunker program was begun in 1986 at the now-closed Tyler State Fish Hatchery. Anglers lend fish weighing 13 pounds or more to TPWD for spawning, and the offspring — more than a million to date — are stocked into the lakes producing entries that season. Costs of the program are paid by sponsors, currently Toyota.
“A large amount of the ShareLunker sponsorship money has been used to develop procedures for DNA testing,” says Forshage. “When the program began, these techniques did not exist, and we felt they were necessary for us to be able to prove our selective breeding program and ShareLunker fingerling stockings work.”
Since January 2004, TPWD has collected tissue samples from every fish entered into the ShareLunker program. Using ShareLunker sponsorship money, TPWD also purchased laboratory equipment and software for use by TPWD geneticist Dijar Lutz-Carrillo.
“Until October 2005, all ShareLunker entries were evaluated using one to three diagnostic markers or not at all,” Lutz-Carrillo says. “New methods incorporate novel genetic markers developed in our lab that provide more accurate estimates of genetic composition and also allow us to go back and evaluate historical samples from large fish, such as archived scales from wall mounts, that weren’t accessible before.”
These new tools also now make it possible to evaluate the relationships among ShareLunker fish.
“If a contemporary ShareLunker is a descendant of a ShareLunker donated to TPWD years ago, we will know — given we collected some tissue or have an old scale or bone from its mom or dad,” Lutz-Carrillo explains.
Before 2001, ShareLunker females were paired with “ordinary” Florida males for breeding. TPWD began Operation World Record (OWR) in 2001. The first phase of the program involved using male ShareLunker offspring to breed with ShareLunker females. A second part of the program sought to evaluate the performance of ShareLunker offspring for their potential to become ShareLunkers, or possibly a world record, themselves. These fish, pure Floridas descended from parents both with ShareLunker genes, were called OWR fish.
In 2005, OWR offspring were raised to 6-inch size and stocked into six public reservoirs. After four years, TPWD used physical and genetic markers to identify these fish, and their growth was compared to wild fish of the same age in those same reservoirs. The OWR fish had greater mean lengths and weights than wild largemouth bass in all study lakes except one.
It takes an average of 11 years for a largemouth bass to reach 13 pounds. We are just now reaching the time when fish whose parentage we can trace are old enough and big enough to become ShareLunker entries — but an angler has to catch one and lend it to the program.
“The introduction of Florida largemouth bass and the implementation of regulations that protect larger fish have had a profound impact on Texas bass fishing,” Forshage says. “The ShareLunker program has provided the funding for the genetic research and the brood fish to make fishing even better. We are waiting for the day when we can look at the DNA test results from an entry and say, ‘That’s our fish.’”
The ShareLunker season runs from Oct. 1 to April 30 each year. To enter a fish, call (903) 681-0550 or page (888) 784-0600 and leave a number. To learn more about the program, including the valuable prizes anglers receive, visit www.tpwd.state.tx.us/sharelunker.
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