September 7, 2008

Pesticides Could Help Control Pesky Gobies Poison’s Use Limited, Could Protect Fishing


Federal researchers have announced that they have discovered certain pesticides can be used to control the voracious round gobies that have invaded the Great Lakes and Mississippi River basin.

The bad news is there probably isn't enough fish poison in the world to kill all the bulging-eyed little fish that have infested North American waters in the last two decades.

Gobies, a native of the Caspian Sea region, were first discovered in the Great Lakes in 1990 and have since spread into the Mississippi River basin. They likely arrived in the ballast of oceangoing freighters traveling up the St. Lawrence Seaway.

The speedy little fish feed on invasive zebra mussels and also the eggs of native fish species. They have been called pugnacious by some biologists because of their ferocious defense of their own spawning sites, and that has had the effect of further squeezing out native species.

Scientists now say two poisons have proved effective in targeting gobies if they are applied in a special formula that spreads across only the bottom 2 inches of a lake or riverbed, but they say their only practical use would be to control goby numbers in limited areas, or to slow their spread into new bodies of water.

The problem is the fish already have spread across the Great Lakes and into the Illinois River. The federal government hoped to halt their inexorable spread across the continent by building an electric fish barrier on the Chicago Sanitary and Ship Canal, but the gobies made it past that artificial link between Lake Michigan and the Mississippi River basin before the barrier was complete.

Work on the barrier continues. But it is now called an Asian carp barrier, because the hope is it will stop a different set of invaders from swimming the opposite direction -- from the Mississippi and into the Great Lakes.

Theresa Schreier, a U.S. Geological Survey biologist and lead author of the research, said the goby poison could be applied in limited areas to protect local fishing.

"Inland lakes definitely would be a possibility," she said.

Perhaps equally important, Schreier said the research showed that targeting poisons in certain areas and in certain ways can be an effective means in controlling unwanted species while sparing many native fish.

"This work shows the value of understanding how an invasive species differs from native populations in the way it lives in an ecosystem and basing control measures on a unique vulnerability of the invader," she said.

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