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« Four More Years Would Be Disaster for Recreational Fishing | Main | California Brothers Deserve Your Support for Fish-a-Thon »
Friday
Aug242012

Carp Are Doing Damage Even When You Don't See Them

These bighead carp were damaging a Missouri pond without the owner even knowing they were there. USGS photo.

The Journal Sentinel offers an in-depth look about the search for techniques to track Asian carp. But first, it presents this anecdote that typifies damage that invasive species can cause with little or no realization of what’s going on:

A fish pond in Missouri reveals just how stealthy Asian carp can be.

Maybe an acre in size, the pond had been stocked with catfish, bass and bluegills. The owner was pumping it full of fish food, yet the fish appeared to be starving. So in early 2010 the owner called in a consultant. 

"They came out with electrofishing gear, caught some fish and looked at them," said Duane Chapman, one of the country's leading Asian carp experts and a biologist with the U.S. Geological Survey. "The fish were emaciated and he didn't know why. He said, 'There's something wrong here. We need to start over again.' They brought in rotenone and completely killed the pond."

Over the next week, the rotting carcasses of about 300 bighead carp surfaced. The smallest were 20 pounds. The big ones were a border collie-sized 35 pounds. Poisoned Asian carp, Chapman explained, are different from many fish species in that they typically don't surface unless the water is warm enough for gases to build up in their bellies, a process that can take a week.

"It was quite amazing there could be that much poundage in one small pond," Chapman said.

It turned out that a decade earlier the previous property owner had stocked the pond with bighead. They had flourished right under the nose of the new owner, who had smelled trouble - but couldn't see a thing.

I found the story especially interesting because grass carp --- illegally introduced by lakefront property owners who should be arrested --- have done the same thing to the small lake behind my house. Those carp, most of them 20 pounds and more, make up the majority of the biomass.

And just as an acre of land can grow only so many bushels of corn, a lake can sustain only so many pounds of fish. As a result, the bass and catfish in my little lake grow slowly, if at all, with the bulk of the bass being 12 inches or less.

Will what has happened in that pond and my lake also occur if/when Asian carp move into the Great Lakes?

Do we really want to wait and see what happens, endangering a billion-dollar sport fishery? The time is long past due to close the manmade connection between the Great Lakes and the Mississippi River basin. Right now, it provides an open door for invasive species to migrate from one system to another.

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