Zebra mussels proliferate, clog water intakes
Zebra mussels first showed up in a small body of water west of Lake Erie in 1988, probably immigrating in a cargo vessel's ballast water.
It's a common route. More than 20 percent of the 1,427 aquatics introduced to the United States — nearly 1,000 of them since 1950 — came via ship.
By 1990, zebra mussels were in all the Great Lakes and many Eastern rivers. They transformed the Hudson in just 16 months, burgeoning to a population of 550 billion and altering virtually every known aspect of the river.
When they made it to the Susquehanna, arriving in the river's New York reaches in 2002, ecologists cringed. Ahead of the creature, clear through Pennsylvania to Chesapeake Bay, were 400 miles of native fish and shellfish that the zebras could smother and out-compete for their diet of algae.
That was far from the only concern. Also ahead were dozens of industrial and municipal water intakes, which the zebras, proliferating like B-movie monsters, could clog.
Now the mussels have shown up in different headwaters — Tioga County's Lake Cowanesque, a tributary that augments the flow of the Susquehanna during dry spells. Officials theorize they may have come in a bait bucket, or on a boat.
How they made the journey almost doesn't matter anymore. A female mussel is sexually mature at two years, and she releases up to a million eggs that the current can whisk downstream.
Yet, for whatever reason, the Susquehanna has proven to be different from other rivers. Its New York mussels moved more slowly than feared.
Now, with the new population from a different source, "it will be interesting to see what happens," says Gary Rosenberg, a malacologist at the Academy of Natural Sciences. "Maybe we can learn something about the habitats they prefer."
Laws restricting the movement of some fish have been enacted in recent years, and Congress is considering strict controls on the release of shipping ballast water for the Great Lakes.
Pennsylvania recently banned the transport of any live fish from the Lake Erie watershed because of concerns about several invasive species and pathogens now thriving there.
— Sandy Bauers