Mini Monsters "Musseling" into Missouri
Experts disagree about the potential geographic limits of the zebra mussel. Already they have penetrated far north into Canada and have been found near the mouth of the Mississippi. The genetic plasticity of the mussels allows them t o adapt to a variety of environments - even salt water.
Researchers now know that zebra mussels seem to prefer hard water, where there is plenty of calcium to build their shells. They can't reproduce in waters that are highly acidic, which may limit their distribution. Because of their preference for solid surfaces, they are seldom numerous in lakes or rivers with muddy or mucky bottoms, however they will attach themselves to plants growing from a soft bottom.
No one doubts that zebra mussels will continue to colonize new waters. Distribution maps can't keep pace with their spread. So far they have tended to move from the Great Lakes along major river systems to the south and east, but they have also been found in numerous landlocked lakes. Although their progress is likely to be slower, zebra mussels will inevitably find their way west. They have already established themselves in Oklahoma, via the Arkansas River.
Zebra mussels have a tremendous and, sometimes, insidious potential to get around. Adults can latch onto barges and boat hulls and be transported upriver. Currents carry billions of their veligers downstream. They may be transported by birds and animals, or they might be swimming in bilge water, minnow buckets or livewells or be attached to boats, motors or trailers. Even when out of the water they can remain alive for several days.
At a check station in the state of California, for example, boats with live zebra mussels attached were intercepted. Those boats had been trailered across the country from the Great Lakes, about 40 hours travel time.
Bob Hrabik told how zebra mussels showed up in a small strip pit in Illinois that was closed to fishing and boating. Investigators concluded that the mussels had been inadvertently introduced by scuba divers, after a check of divers who dove in infested waters revealed as many as 200 zebra mussel veligers on each of their suits.
How hospitable Missouri waters will be to the zebra mussels is still in question. Miller said the fact that they have not yet been found in the Missouri River may indicate that they may not be able to tolerate its strong current and muddy water. However, other