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Invasive Asian carp may have gotten past the last line of defense to keep them out of Lake Michigan. DNA samples from water indicate both big head and silver carp have gotten beyond a new $9 million electric fish barrier in the Chicago Ship Canal. But state and federal regulators still want to catch an actual fish to confirm that.
John Lodge, a biologist at the University of Notre Dame, has developed this D-N-A sampling of the environment. The method detects the presence of carp from things like skin cells they leave behind in the water. And he says the tests are very accurate.
"There's no reason to think the carp aren't present when the D-N-A is detected," says Lodge.
Resource managers worry that should Asian Carp get loose in the Great Lakes they will wreak havoc. They can grow more than 5o pounds and eat 40% of their body weight every day. They feed on the same small critters at the base of the food chain that all other fish in the lake depend on.
Researchers can't tell when the carp got beyond the barrier. It could have been a week ago or it could have been a year. This new DNA sampling only began last summer. For years an electric barrier in the water has acted to repel fish that enter it. A second electirc barrier was built last summer. The first barrier was turned off from time to time for maintenance and knocked off by lightning.
The Army Corps of Engineers plans to shut off the new barrier for a few days early next month for maintenance. But this time, resource managers will poison about a six mile stretch of the canal to kill all the fish.
Researchers want to take more samples above the electric barrier. They don't know how many Asian carp may have gotten past it. But they say even if some reach Lake Michigan, it's not a given that the non-native carp will adapt, thrive and spread. So it's worthwhile to continue to keep up the defenses and perhaps add new ones.