Catch-And-Release Angling Impacts Bass Evolution, Angling Vulnerability

By on July 7, 2015
Hessenauer moves individuals from fasting pens into the respirometry. (Credit: Amanda Hessenauer)

Many anglers practice catch-and-release fishing to keep fish populations strong for generations to come.

However, a new study from the University of Connecticut suggests that even this sort of fishing can have long-term impacts on the evolution of certain targeted species.

A paper detailing the study’s findings is published online in PLOS One.

The study was inspired by similar research conducted in the early 1990s, according to Jan-Michael Hessenauer, who led the recent study as a doctoral student at UConn.

”The Connecticut Department of Energy and Environmental Protection were doing surveys of all the inland lakes in Connecticut, including a few reservoirs owned by drinking water companies,” Hessenauer said. “They found that fish in drinking water reservoirs were four to six times easier to catch than in other lakes.”

It seemed, Hessenauer said, that these relatively unfished reservoirs were producing less wary fish than other water bodies in the area. But the research methods at the time hadn’t progressed enough to address the impacts of angling on fish, and it wasn’t until 2009 that another study showed that angling vulnerability was indeed a heritable trait.

In the fall of 2012, Hessenauer and a team of researchers used electrofishing and netting to capture young-of-the-year largemouth bass from two unfished drinking water reservoirs, as well as two popular public lakes.

Bass inside respirometry chamber. (Credit: Jason Vokoun)

Bass inside respirometry chamber. (Credit: Jason Vokoun)

The sampled fish were placed into a single pond and marked with fin clips and visual-implant elastomer tags so the researchers could tell the populations apart.

“We basically just left them in the pond to do their thing,” Hessenauer said. “We periodically stocked the pond with minnows to keep the bass fed and happy.”

After a year of growth, the researchers tested the resting metabolism rates of the fish using a process called respirometry.

They found that fish from the protected reservoirs exhibited significantly higher metabolic rates than those from the public lakes. Higher metabolisms force the fish to seek food more frequently, making them more vulnerable to angling. Those fish also tend to experience greater reproductive success.

Furthermore, fish from the public lakes seem to learn to avoid lures more quickly than those from the unfished reservoirs. So if you feel like the fish at your favorite spot are getting smarter, you’re not entirely wrong.

“I think that the biggest surprise was that we found the signal,” Hessenauer said. “We were expecting the fished lakes to have lower metabolic rates than the unfished lakes. We were just surprised by how clear the difference was.”

Hessenauer says he doesn’t want to imply that recreational fishing is having detrimental effects on fish populations. In fact, increased catch-and-release angling could be more of a problem for the anglers themselves.

“If anything, the fish may be harder to catch, so angler trips may not be as satisfying,” Hessenauer said. “What this means is that fisheries managers may need to try different management strategies.

“Catch-and-release is the dominant paradigm for largemouth bass in the north, where management is typically based on controlling harvest. Managers and anglers may need to work together to develop new strategies to maintain bass populations.”

Top image: Hessenauer moves individuals from fasting pens into the respirometry. (Credit: Amanda Hessenauer)

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