Asian carp present longterm challenge to state officials

By T.W. Budig
ECM Capitol Reporter

Federal researchers hope to perfect a designer application process for poisoning Asian carp while sparing other forms of aquatic life.

But Mark Gaikowski, supervisory biologist at the federal Upper Midwest Environmental Sciences Center in La Crosse, WI., doesn’t believe an overall curative exists for eliminating the invading species.

Looking rather harmless, these bighead carp fingerlings can grow into 50 pound fish that studies suggest can threaten the viability of native fish populations. The fingerlings pictured are from the lab in the federal Upper Midwest Environmental Sciences Center in La Crosse, Wis. (Photo by T.W. Budig)

“I don’t think we’re ever going to eradicate silver carp or bighead carp — I don’t know that you can do that in such large (river) systems,”  Gaikowski said.

“We have the potential to impact their population. But I don’t think we have the potential to eradicate them at this time,” he said.

Interest in Asian carp, exotic species brought to the United States some 40 years ago for use in aquaculture ponds but later escaping during floods, was renewed recently by the detection of silver Asian carp DNA in the St. Croix River.

“That was a surprise,” said Tim Schlagenhaft, of the Minnesota Department of Natural Resources.

Bighead carp — both bighead and silver carp can reach a whopping 50 pounds or more — have been caught in Minnesota waters before, he noted.

But the possibility silver carp, too, may be plying home waters was something new.

Silver carp are something of the media darlings of Asian carp species for their habit of leaping out of the water and smacking boaters and water skiers, a habit reportedly not seen in their native home range.

Asian carp grow fast and are voracious feeders. They compete for food with native aquatic life, and studies have shown in waters with high Asian carp populations the fatty acid profiles in native fish are significantly reduced.

“So if you have that dramatic shift in fatty acid levels, that has potential implication for growth, for survival, for reproduction — a whole host of different things,” Gaikowski said.

Native predators may feed on young Asian carp. Indeed, biologist look to healthy native fish populations, habitat improvement, as a means of combating the invader.

Still, Asian carp may grow so fast as to quickly outsize native predators.

While factors like water clarity may limit the range of Asian carp in North America, it’s believed cold weather will not. The geographical latitude of their native home range suggests Asian carp could thrive as far north as Canada.

Researchers look to using the feeding habits and unique biology of Asian carp in crafting control measures. For instance, with the exception of some native shad, Asian carp feed on materials much smaller than most native fish.

“They’re very, very effective filter feeders,” Gaikowski said. “We’re trying to develop a system to package up those (toxic) compounds into a particular that can be primarily filtered out by silver and bighead carp”

Further, in crafting the designer application system, researchers hope to use unique enzymes found in Asian carp to help trigger the toxin. They want to pinpoint where the toxin winds up rather than just applying it in a general way so that all the species within a given body of water receive about the same dose.

In order to speed up development, researcher look to using an already registered fish toxin in designing their Asian carp control.

Environmental Sciences Center Supervisory Biologist Mark Gaikowski explains the workings of the center’s lab. The tanks to the left contain sea lamprey, one of the species the center conducts research on. (Photo by T.W. Budig)

It could be several years before an application is ready for general use, Gaikowski indicated.

That researchers are dealing with an unusual species can be seen in the lab in the basement of the La Crosse facility. The large blue tanks holding thousands of small bighead and silver carp bring to mind a bait shop.

That’s until noting doors are locked, wastewater is treated at the facility before discharge, and that leaving the lab involves walking over a mat soaked in disinfectant.

Other related research taking place at the center involves the DNA sampling that indicated the presence of silver carp in the St. Croix.

Although the test may seem conclusive — DNA evidence often portrayed as the ultimate fingerprint in crime dramas — Gaikowski suggests the evidence is tenuous.

Indeed, it’s possible, one federal biologist theorized, there are no silver carp in the St. Croix, nor has there ever been. It’s possible a boat struck a silver carp down river and the carp remains became fastened to the boat.

Later, as the boat plied the St. Croix, the boaters unknowingly seeded the DNA.

It’s even conceivable a pelican could have fed on Asian carp at a distant place and later spread the DNA into the St. Croix through defecation.

So researchers hope to improve the accuracy of the DNA sampling process.

Swirling fingerling Asian carp can be seen through the window on one of the fish tanks in the center lab. (Photo by T.W. Budig)

The Minnesota DNR thus far in its electronic shocking and commercial netting have not yet seen a silver carp brought to the surface.

While the silver carp DNA was unexpected, the idea that Asian carp are at the watery doorstep of Minnesota didn’t surprise the DNR.

“It certainly didn’t throw any of the agency folks into a panic,”  Schlagenhaft said, noting the same may not be true of St. Croix waterskiers.

Asian carp have been caught before, he noted.

Like Gaikowski, Schlagenhaft views Asian carp as an ongoing problem. “I do,” he said.

He compares the carp to the sea lamprey, which helped decimate Great Lake trout decades ago but which were eventually brought under control.

Forty years ago when people imported exotic species like Asian carp into the United States there just wasn’t an appreciation of the risks, Schlagenhaft explained. Laws have been tightened, he said.

Schlagenhaft is DNR point man in an ad hoc group of state and federal officials who share information on Asian carp. “They’re ahead of us in the game,” he said of agencies down river in dealing with the carp.

Commercial fishermen do not net anything like the number of Asian carp in northern waters than they do to the south,  officials said.

Gov. Mark Dayton said on Tuesday,  Aug. 23 the state would do everything possible to prevent the spread of Asian carp.

“I was encouraged that they didn’t find with the netting any actual Asian carp, but that’s not definitive,”  Dayton said  of DNR operations. “We need to take every measure possible, and we’re going to do that.”

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