Study says grass carp have invaded three Great Lakes

Associated Press

TRAVERSE CITY, Mich.

Invasive grass carp have reached three of the Great Lakes and pose a significant environmental risk there, but time remains to prevent them from getting out of hand, according to a scientific analysis released Friday.

The voracious grass carp is among four Asian carp species threatening to reach the world’s largest surface freshwater system. Bighead and silver carp, the most feared, would compete with native fish that eat microscopic plants and animals, while grass carp feast on aquatic vegetation that provides crucial habitat and spawning grounds.

Grass carp have been found in Lakes Erie, Michigan and Ontario, although it’s uncertain how many there are or how widely they have spread, U.S. and Canadian researchers said. At least some are reproducing.

“For the first time, we have a binational, peer-reviewed study by some of the best minds and practitioners in the field who have a consensus on what the risk is to the Great Lakes from grass carp, and it’s pretty substantial,” said Marc Gaden, spokesman for the Great Lakes Fishery Commission.

Grass carp were introduced to the U.S. in the early 1960s to control weed growth in waterways. Like other Asian carp, some escaped into the Mississippi River and have migrated northward toward the Great Lakes.

It has long been known that at least a small number of grass carp were in the lakes, Gaden said. Some may have slipped into Lake Michigan through a Chicago-area waterway network before electric barriers were erected to block fish migration. People might have released others, intentionally or by accident.