Photo: Felicia Fonseca, File / AP Photo
While officials have been feverishly trying to keep the dreaded Asian carp from making its way into the Great Lakes -- using tactics that range from poisoning to electric blockades -- scientists now say that the tiny quagga mussel has already done the damage. The mussel is causing unprecedented changes in the lower food web in Lake Michigan, perhaps making the territory inhospitable to the voracious carp.
"It's estimated that there are over 500 trillion dreissenids (freshwater mussels) currently in Lake Michigan," says Gary Fahnenstiel, senior ecologist for NOAA's Great Lakes Environmental Research Laboratory in an interview with Slashfood.
The thumbnail-sized striped quagga mussel is a filter feeder. They were first spotted in Lake Michigan in the early 2000s, likely finding their way there in the ballast tanks of ships originating in the Caspian Sea. As their population continues to grow, quagga mussels have significantly decreased the amount of phytoplankton in the water. That plankton forms the basis of the food chain, which supports native species like lake whitefish, deepwater sculpin and alewives.
"The water has never been clearer in Lake Michigan," says Fahnenstiel.
That's bad news for fish who rely on plankton for food, say researchers in a series of scientific papers that were published in the current issue of the Journal of Great Lakes Research. According to an Associated Press story, fish like whitefish and salmon are smaller in size because they are likely getting less nutrition.
"Whitefish actually eat the mussels, but the mussels are very low in nutrition, so the fish aren't getting as much energy when they eat as they used to," says Steven Pothoven, a NOAA fishery biologist.
While officials have been worried the Asian carp could spread to the Great Lakes, and eventually collapse the $7 billion fishing industry, some say the reduction of plankton caused by the booming quagga mussel population means the carp won't be able to flourish. Other scientists disagree and say the Asian carp can thrive, and remains a serious threat.
"They can eat other things besides plankton," said Duane Chapman, a U.S. Geological Survey fisheries biologist to the AP.
But Fahnenstiel says the immediate threat to the lakes remains the quagga mussel.
"If people want to buy them one for a dollar, we'll get rid of our debt real quickly," he says.