Zebra mussels (Dreissena polymorpha) are small, fingernail-sized mussels native to the Caspian Sea region of Asia. They are believed to have been transported to the Great Lakes via ballast water from a transoceanic vessel. The ballast water, taken on in a freshwater European port was subsequently discharged into Lake St. Clair, near Detroit, where the mussel was discovered in 1988. Since that time, they have spread rapidly to all of the Great Lakes and waterways in many states, as well as Ontario and Quebec.
Diving ducks and freshwater drum eat zebra mussels, but will not significantly control them.
Likely means of spread: Microscopic larvae may be carried in livewells or bilgewater. Adults can attach to boats or boating equipment that is in the water.
...researchers have raised yet another possible downside of the economic crisis. Global merchant vessels are sitting idle at ports, potentially accumulating marine organisms that could be carried to other parts of the world when business picks up.
Ships that transport organisms on their hulls have likely helped non-native marine species invade new habitat around the globe, resulting in damage to both ecosystems and economies. Coating the hulls can prevent “biofouling,” but many of these treatments lose their effectiveness on inactive ships. For instance, a 200-meter ship could amass more than 20 tonnes of organisms if left unused for a long period of time, the authors write.
More on invasive species here (I think this is the site I got the zebra mussel info -there was a long, but necessary gap in the writing of this post - my son wanted to play outside).
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