Asian Carp Part II: Another Unwanted, Expensive Invader
Written by triplepundit   
Wednesday, 03 February 2010 15:45
Despite the erection of physical barriers and, as I noted in a post last week, the enterprising solutions aimed at overfishing them into extinction, it might already be too late to fully protect the Great Lakes from their next greatest threat: the Asian carp. The DNA of Asian carp have been detected in Lake Michigan.

Much of the ink on this story has been about the impact Asian carp could have on the Great Lakes fisheries—based on the assumption that the fish would out-compete native species for food. The fisheries have reason to worry, based on a long, ugly history of invasive species in those important bodies of water.

Take the sea lamprey. That parasite entered the Great Lakes way back in the 30s and 40s, decimated native lake trout populations by literally sucking the blood right out of the fish. According to the Great Lakes Fisheries Commission, “under some conditions, only one of seven fish attacked by a sea lamprey will survive.”   Since the sea lamprey’s accidental introduction to the Great Lakes, the amount of Lake Trout in Lake Huron and Lake Superior fell from about 15 million pounds to only 300,000 pounds, according to The Great Lakes Wiki.

Through a number of measures, including using toxic “lampricides” to kill sea lamprey larvae, U.S. and Canadian agencies have been able to control the sea lamprey population in the Great Lakes down to just 10 percent of its historic highs. But it comes at a great price—about $17 million, annually, is spent on keeping this species in check. And there are many other invasive species that scientists have not been as successful in controlling.

The damage that invasive species cause extends well beyond fisheries’ bottom lines.

“Alien species are second only to habitat destruction as a cause of biodiversity erosion,” says Stephanie Mills, author and the Fellow of Biodiversity and Bioregionalism at the Post Carbon Institute, a think tank that develops programs to educate the public on climate change, energy scarcity and other matters of sustainability.  “So it would be a good time to say we need to sit down as a society [and address this issue]. So we can leave a legacy of some biodiversity.”

But just how much of a threat does the Asian carp pose to the Great Lakes? Despite evidence of the carp DNA in Lake Michigan, Mills says there is some debate as to the quantity of the fish that would need to infiltrate the waters before a breeding population could be established in the lakes. “But why risk it?” she asks. “Here is an argument for invoking the precautionary principle.”

If the carp does get a stronghold in the lakes, biologists will work in concert with the US Army Corps of Engineers and other agencies to develop containment strategies, but the costs of those actions will likely be astronomical and–if the sea lamprey is any indication–enduring. Plus, there’s no telling how much damage the carp–which can eat 40 percent of its body weight in a single day and can grow to 100 pounds–will do to the biodiversity of the Great Lakes before it is contained.

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