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U.S. seeks new weapons against dreaded Asian carp

Thu, 28 Apr 2011 21:16 GMT

Source: reuters // Reuters

* Invasive Asian carp pose many problems - scientists

* Stopping carp may involve poison particles, water guns

* Studies may take too long, opponents fear

By Andrew Stern

CHICAGO, April 28 (Reuters) - Asian carp are hardier than scientists previously thought, with the invasive species capable of surviving in the Great Lakes by bottom-feeding, U.S. officials said on Thursday.

The voracious and prolific Bighead and Silver carp are considered a dire threat to the lakes' $7 billion fisheries, sucking up plankton and crowding out other species. The carp have surged up the Mississippi River system within 25 miles (40 kilometres) of three electrified barriers erected in a Chicago-area canal to block their progress.

Last year, scientists initially concluded there was not enough plankton to sustain carp in Lake Michigan. But they recently learned Silver carp will eat Cladophora, a plentiful algae that thrives on fertilizer runoff, while Bighead carp can survive on detritus on the lake bottom.

"Initially we thought this was a wasteland" for carp due to the lack of plankton, said Leon Carl of the U.S. Geological Survey, which is conducting studies on the still-mysterious invaders and ways to stop them.

"The next question is, can they actually grow and thrive on it, and go somewhere they like even better?" he said on the sidelines of a public hearing on the issue.

The Obama administration has fought to keep open man-made waterways connecting the Mississippi River basin to Lake Michigan that are considered vital links by commercial shippers, boaters and tour boat operators. More than $100 million spent on carp control had been diverted from funding for Great Lakes restoration projects.

Environmental groups object to the funding diversion and back a lawsuit by Michigan and other Great Lakes states that demands a permanent physical separation of the two watersheds.

TIME FOR SOLUTIONS

"We had information today that there are no Asian carp near the electric barriers so we believe we have time to work on solutions," said John Goss, a White House appointee overseeing the effort.

Several weapons are being investigated to combat carp.

Scientists have tested 240 compounds and isolated 10 that could be carp pheromones -- chemicals that would attract carp so they can be harvested or killed. They are also trying to create tiny particles of fish poison that would lodge only in the fine gills of Asian carp. And they are experimenting with powerful "water guns" to deter carp.

A new problem scientists discovered is that carp can spawn on shorter waterways than previously thought, creating the need for more widespread monitoring, Carl said.

It is possible carp will eat themselves out of existence, or succumb to over-fishing as happened in their native China. Last week, fishermen gathered up 42 tonnes of carp, and Goss set a target of 1 million tonnes. The catch is mostly shipped to China.

Invasive species have plagued the Great Lakes for decades, most arriving in the ballast water of ocean-going ships. Invasive sea lampreys were fought successfully with pheromones and poison, officials said. But zebra mussels have thrived, filtering water and helping algae grow that carp may feed on.

Fisherman Mike Ohlinger said carp needed to be dealt with today, not tomorrow. "It's just as bad a problem as we have in the Gulf of Mexico," he said referring to the 2010 oil spill.

(Editing by Philip Barbara)