June 12, 2009

Zebra mussels lose ground to cousin

Invasive quagga mussels are replacing their equally destructive cousin, the zebra mussel, in calmer waters in the Great Lakes, Wisconsin researchers said.

While zebra mussels still dominate in fast-moving streams and rivers, the larger quagga mussels prefer soft lake bottoms of sand and silt, said Suzanne Peyer, a doctoral candidate in the zoology department of the University of Wisconsin, Madison.

Zebra mussels prefer to attach to hard surfaces, such as rocks, gravel, pipes and ship hulls, she said in statement Friday.

Quagga mussels may be the reason Diporea, a shrimp-like species that is a food source for larger fish, is no longer abundant in the Great Lakes. Whitefish that feed on Diporea are growing to less than half of their expected size, said Peyer's study, published in the Journal of Experimental Biology.

Zebra mussels hitchhiked their way to the Great Lakes in the late 1980s, with quagga mussels arriving a few years later.