An Asian carp that escaped American fish farms into the Mississippi in the 1990s now threatens the ecosystems of the Great Lakes, the world’s biggest freshwater lake system.
The bighead and silver carps, consuming up to 40 percent of their body weight daily in plankton – starving out other less aggressive species – can considerably exceed one metre in length and 50 kilos in weight.
Aside from threatening species that are traditionally popular with anglers – a $7 billion enterprise in the Great Lakes – and commercial fishermen, the Asian carp are known to leap from the water at the sound of passing motors, colliding with boaters.
In 2002, the US Army Corps placed electronic devices in the waterway south of Chicago, linking the Mississippi to Lake Michigan, intended to stave off the carp by emitting electrical pulses, or even giving the fish small jolts. That system was even replaced with a more powerful one this year, but scientists have now found DNA trace of the species north of that barrier, with the navigational lock on the Calumet River as the only remaining obstacle for the carp’s migration north into Lake Michigan, and then, possibly, Lake Superior, Lake Huron and Lake Erie. There is still some uncertainty, however, how the species would fare in the Great Lakes, much chillier and a different ecosystem from the rivers.
Still, a worst-case scenario, according to Cameron Davis, a senior Great Lakes Advisor with the US Environmental Protection Agency, would be the Asian carp spreading “like a cancer cell” in that lake system, the biggest in the world.
“We’re going to keep throwing everything we possibly can at them to keep them out”, he added.
Authorities are planning to use toxin to that end, but environmental groups claim that much stronger measures are needed, including closing the locks into Lake Michigan. That would however be heavily opposed by the barge companies trafficking the waterways.