Sponging Off Mussels

Waging war on zebra mussels

• NWF Staff
• Feb 01, 2000

For a native sponge in the Great Lakes, zebra mussels apparently make great growing platforms. Or maybe the sponge is waging war on the alien invaders, in competition for food. Whatever the reason, the sponge has been smothering and starving zebra mussels at least since the early 1990s, when scientists noticed the trend on a reef and a shipwreck in Lake Erie. The mussels, meanwhile, notorious for clogging pipes and water-treatment plants, have spread into the Ohio and Mississippi River drainage systems.

Now there´s evidence the sponge could be making a significant dent in zebra mussel populations; in one Great Lakes study area the pests´ numbers have dropped by 20 to 40 percent. The mussels also have been discovered by predators, and their overall numbers have fallen somewhat over the years.

But that news is not all good. One of the predators is the goby, a fish native to eastern Europe. Like the zebra mussel, it apparently hitched a ride in ship ballast water. The small but aggressive fish now inhabits all five lakes. Along some shorelines it is the dominant fish, and biologists fear it could crowd out native fish species. Scientists also are concerned about other invaders in the region, including the Eurasian ruffe, another pint-sized bully.