Leeches are getting into the mouths of largemouth bass. Researchers want to know how.

Video do bass eat leeches


Chad Boyce inched the hunter-green johnboat along the shoreline of a Back Bay creek. A pair of spider-like arms on the vessel’s bow held wires that dipped into the water.

He flipped a switch and within seconds, dozens of spastic fish rose to the surface – shocked by a light electrical current.

Dave Gauthier frantically searched for largemouth bass, scooping them into a net while leaving dozens of shad, mullet and bluegill to recover on their own. Just as quickly as they were stunned, they soon would swim off as if nothing happened.

The bass, however, ended up in a tank for examination. Before getting released, they’d be checked for leeches in their mouths.

Boyce, a fisheries biologist with the Virginia Department of Game and Inland Fisheries, discovered several years ago that some of the bass in the vast estuary covering the southern end of Virginia Beach had small leeches on the roofs of their mouths.

Stumped as to why, he reached out to experts to find one who would be interested in state-sponsored research. Gauthier, an associate professor of biological science and an aquatic animal disease expert at Old Dominion University, jumped at the chance. Previously he’d studied a bacterial infection showing up on striped bass in the Chesapeake Bay.

Along with graduate student Amanda Pomposini, the three are making progress in trying to figure out how the leeches are getting into Back Bay , and whether or not the blood-suckers are having adverse effects. North Carolina fisheries biologists noticed the leeches in Currituck Sound bass and are sharing information with the Virginians.

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The project is especially important to Boyce, because he has led an effort to bring Back Bay closer to its heydays of the 1970s and 80s – when its bass fishery was regarded as one of the best in the country.

“We’re stocking and doing surveys and trying to work to make fishing here better,” Boyce said. “I want to know what this all means to the fishery.”

The trouble was that the three were dipping into uncharted waters.

“Nothing of any substance has been written about this,” Gauthier said. “There hasn’t been any research done.”

So the trio started by shocking bass, then weighing, measuring, tagging and examining them for leeches or signs that they had leeches in the past. Tagged and recaptured fish are valuable because the biologists can see whether leeches are still attached or not, and whether the fish have suffered damage because of the parasites.

The leeches are showing up in the bay by piggy-backing on blue crabs. Samplings of crab pots in the bay show that most crabs carry leech cocoons, small black blobs that unleash larvae.

But that discovery led to more questions : How are baby leeches getting into the mouths of largemouth bass? The crabs tend to be found in deeper waters of the middle bay, while most of the bass stick to shoreline cover and old duck blinds. And bass don’t eat blue crabs.

“The million-dollar question,” Gauthier said.

So the trio next week plans to employ crawfish traps to see whether the little lobster lookalikes are carrying cocoons. Crawfish are high on bass’s menu of favorite foods.

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“If the crawfish have (cocoons) we might just have our answer,” Gauthier said.

The leeches don’t appear to be causing problems for the bass. When they detach from the roof of the mouth, they leave small sores that eventually heal. And their presence isn’t causing damage to the fish’s vital organs.

“We’ve swabbed the wounds to look for bacteria or viruses, and it’s all come up negative,” Gauthier said. “We’ve looked to see if stress hormones are elevated because of the leeches and that’s come up negative. The leeches don’t appear to be affecting feeding or reproductive habits.”

Which is all good news to Boyce and his efforts to make Back Bay once again an incredible fishery.

“It’s making a good comeback,” Boyce said. “Grasses are returning, bass fishing is getting much better, and other species are more plentiful.

“We just wanted to make sure these leeches weren’t going to ruin any of that. And we’re pretty convinced that it’s not.”

Lee Tolliver, 757-222-5844, lee.tolliver@pilotonline.com Follow @LeeTolliver on Twitter.

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Ethan Smith is a seasoned marine veteran, professional blogger, witty and edgy writer, and an avid hunter. He spent a great deal of his childhood years around the Apache-Sitgreaves National Forest in Arizona. Watching active hunters practise their craft initiated him into the world of hunting and rubrics of outdoor life. He also honed his writing skills by sharing his outdoor experiences with fellow schoolmates through their high school’s magazine. Further along the way, the US Marine Corps got wind of his excellent combination of skills and sought to put them into good use by employing him as a combat correspondent. He now shares his income from this prestigious job with his wife and one kid. Read more >>