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, the AP reports. 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, US and Canadian researchers said. At least some are reproducing. A spokesperson for the Great Lakes Fisher Commission says the risk to the Great Lakes is "pretty substantial."
Grass carp were introduced to the US in the early 1960s to control weed growth in waterways. Some escaped into the Mississippi River and have migrated northward toward the Great Lakes. They've been turning up more often in recent years, and the threat of a full-fledged invasion appears to be rising. The analysis said it is "very likely" that grass carp will become established in Lakes Erie, Huron, Michigan, and Ontario within 10 years unless effective steps are taken to stop them. Researchers are studying how to prevent that. Tougher enforcement of laws against bringing them into the region would help, along with greater care to prevent release of fertile fish from hatcheries.