Zebra mussels (Dreissena polymorpha) are one of the most catastrophic aquatic invasive species in North America. Native to Russia and Ukraine, these fingernail-size mollusks have spread around the world, often carried in ballast water—used to stabilize boats—as larvae, where they’ve caused billions of dollars of damage to fisheries, water treatment facilities, and other aquatic industries by clogging intake pipes and robbing nutrients from ecosystems. Now, researchers have discovered a new way they invade—by hitchhiking on fish.
The scientists made the observation while assessing fish communities in a lake in southeastern Quebec last year. They found a zebra mussel attached to a lake chub (Couesius plumbeus), a species of minnow typically about 12 centimeters long. The observation, reported this month in Biological Invasions, is the only time a nonlarval freshwater bivalve has been seen attached to a fish. The mollusk had latched onto the hapless minnow (pictured above) using protein fibers called byssal threads, which they also use to attach to plants, rocks, and concrete.
The discovery is particularly concerning because fish are highly mobile organisms that don’t have a means of removing these parasites. And lake chub and similar species are often used as bait by anglers, which means they’re frequently carried from one body of water to another.
Though boaters and others who use infested waters for recreation are warned to wash their watercraft, remove any clinging plant matter from their equipment, and discard any water they might be carrying before traveling to another body of water, those who use baitfish are likely unaware that they may be inadvertently transporting zebra mussels, the authors fear. The discovery, they argue, suggests additional vigilance may be necessary to slow the spread of zebra mussels to new locations.
Source : Science