Bait that's become an invasive species

May 21, 2006|By CANDUS THOMSON

Jay Kilian and Ron Klauda hope anglers take the bait this season.

Take it home. Take it to the trash. Take it to a neighbor who's going fishing the next day. Do anything with their leftover bait but toss it in the water.

For the past several years, the two biologists have watched helplessly as one former bait bucket resident has made itself at home in Maryland waters, taking over turf previously held by native stock.

At nearly 6 inches long, the virile crayfish is both edible and a dandy bait. When Kilian holds up a large one pulled from Morgan Run, one of the region's premier trout streams, you start thinking about getting a pot for a crawdad boil.

But when he starts talking about its potential to ruin streams like Morgan Run, Timber Run and the Gunpowder, it's easy to lose your appetite.

The virile crayfish, a western native, was introduced into the Patapsco River near Woodstock around 1885. Kilian says early documents indicate they probably came from Baltimore fish markets or from bait buckets.

There's not another mention of them until the early 1960s, when biologists collected samples and noted that the virile crayfish had expanded from a few areas to most of the Patapsco River basin. With that hostile takeover came the loss of the much smaller, native Appalachian brook crayfish and the spinycheek crayfish.

But the virile crayfish didn't stop there. By 1997, the invasive critter had established itself in the Gunpowder, Bush, Susquehanna, Patuxent and Potomac rivers.

"They reproduce fast and they grow fast so they colonize rapidly," Kilian explains. "They can move from mouth to mouth in the upper bay. Freshwater fishermen use them as bait and accidentally moved them around in their bait buckets."

And where you find virile crayfish, you find degraded habitat.

"What came first, the virile crayfish, which displaced the native crayfish, which cause the stream to become degraded, or the streams degraded and that allowed the virile crayfish to flourish?" Klauda says. "We don't have the historical record to make that determination."

The Department of Natural Resources is taking steps to give scientists a baseline and periodic assessments of conditions. In 1997 and 2004, biologists conducted stream surveys statewide, providing information that will allow Klauda and Kilian to gauge the virile crayfish's destruction.

What they fear is that as the virile crayfish continues to flex its pincers, it will do to other fish food sources what it did to the native crayfish. Larval amphibians and fish eggs will become the next thing on the menu. Then small trout and bass will be duking it out with the invader.

"A 12-inch largemouth bass and a 6-inch virile crayfish. I imagine the fish would have quite a fight on its hands," Kilian says.

With 350 species, North America has the most diverse population of crayfish. Maryland is home to 10 varieties, two of which are nonnative: the virile and the red swamp crayfish.

The virile crayfish problem goes beyond Maryland. Populations have been reported in Massachusetts, Maine, Vermont, Arizona and California. The species also has been found in Mexico and Europe. Last year, the North Carolina Wildlife Commission passed a regulation to ban possession of the virile crayfish.

When the Nature Conservancy published its list of most imperiled North American fauna in 1997, native crayfish were second only to freshwater mussels.

"They're highly competitive," Kilian says of the virile crayfish. "They'll eat each other and they'll eat all crayfish young."

Klauda and Kilian have no illusions that they can eliminate the virile crayfish from Maryland waters. In that way, they are like biologists battling the northern snakehead, which arrived from Asia five or six years ago to upset the ecological balance in the Potomac River and its tributaries.

And like the snakehead, the virile crayfish is a tough customer. It can survive out of water for long periods and can move over land to another stream.

But the federal government made the importation and transportation of snakeheads illegal in 2001; virile crayfish are legal bait in Maryland, easily bought at many of the region's tackle shops.

What Klauda and Kilian would like to do is stop the virile crayfish from infesting other streams.

"We'd like anglers to think about what they're buying and what they're doing with what's left in their bait bucket at the end of the day," Klauda says. "Freeze or destroy what you have left. If you catch your own crayfish, put them back in the same water you took them from."

While the biologists acknowledge it can be difficult to identify a virile crayfish from a native variety, they say the size of the virile often gives it away.

"Be responsible," Kilian says. "Once the virile crayfish is introduced to a stream, it happens fast. Once they're established, it's boom, bye-bye native." candy.thomson@baltsun.com

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