A fish’s ability to avoid the hook may be more than luck. Research on largemouth bass has shown that some are genetically inclined to be easier to catch, a trait that enables other bass to grow disproportionately large.

With the June 15 opening of bass season, anglers in Pennsylvania joined in the pursuit of the most popular sportfish in America. The state record, caught in Adams County in 1983, weighed 11 pounds 3 ounces. Micropterus salmoides grows bigger in Southern waters where the growing season is longer and warmer.

Anglers debate whether whoppers get big because of what they eat or where they live, but a study at the University of Illinois found that some largemouth bass owe their longevity and size to their parents’ genes.

In an experiment spanning more than 20 years, researchers discovered that vulnerability to being hooked is a heritable trait among largemouth bass. Curiously, it is not a genetically passed physical propensity for fast growth. On the contrary, researchers found some bass get big because other bass are inherently more likely to get caught.

“The potential for angling to have long-term evolutionary impacts on bass populations is real,” David Philipp, an ecology and conservation researcher at the University of Illinois, wrote in a project overview published in the journal Science Daily. “If we truly want to protect this valuable resource into the future, then we need to understand that and adjust our management strategies.”

In the study, fishing was strictly controlled on a 15-acre research impoundment run by the Illinois Natural History Survey. Anglers reserved blocks of fishing time and put every fish caught in a livewell. The fish were measured, tagged to track how many times each had been caught, and released.

“We kept track over four years of all of the angling that went on,” Mr. Philipp told Science Daily. “Many fish were caught more than once. One fish was caught three times in the first two days, and another was caught 16 times in one year.”

After four years of documenting the catch, the lake was drained and researchers collected more than 1,700 fish.

“Interestingly, about 200 of those fish had never been caught, even though they had been in the lake the entire four years,” Mr. Philipp said.