U.S. Biologists Seek Ways to Stop Alien Mussel Invasion

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Since May, scuba divers and groups of workers armed with syringes and plastic buckets have been collecting Higgins' eye pearly mussels. They intend to produce young Higgins' eyes at the service's Genoa National Fish Hatchery in Genoa, Wisconsin, for eventual release back into their natural habitat.

"Our goal with the hatchery project is to take adult Higgins' eye mussels from areas already infested with zebra mussels, raise young mussels in the hatchery, and then release them in areas where they should be safe from that threat," said Pam Thiel, fisheries biologist with the Fish and Wildlife Service. "We hope we can keep this species going in the hatchery and in some remaining suitable natural habitats to prevent zebra mussels from eliminating the Higgins' eye."

Fisheries supervisor Benjamin said "Zebra mussels have the ability to impact our ecosystems. They like the algae [that] fish like, so they're competing with our fish for food. But they don't like the blue-green algae that can foul many lakes and rivers, and in fact, they're adding to the problem because they release ammonia- and phosphorus-containing waste products that may fuel blue-green algae blooms."

In fact, respiratory demand and waste products released by 30 acres (12 hectares) of zebra mussels requires roughly the same amount of dissolved oxygen required to break down the organic material discharged by the Twin Cities Metropolitan Wastewater Treatment Plant, water-quality specialist Sullivan said.

That oxygen demand contributed to unusually low dissolved oxygen concentrations in portions of the Mississippi River during the early summer periods of 1997 and 1998, stirring fears of fish kills.

Caution Urged

This summer's sampling for larval zebra mussels is important in helping verify that the relocated native mussels are living in hospitable sites. The sampling involved collecting water from below the locks and dams stretched along the 500 miles (800 kilometers) from the Hastings Dam below St. Paul, Minnesota, to Keokuk, Iowa, and on large tributaries, including the Chippewa, the Black, the Wisconsin, and the St. Croix, Sullivan said.

These hard-working biologists are warning people to clean their boats and trailers carefully to prevent zebra mussels from moving into new lake and riverine systems. Larvae can be carried in bilge water, bait buckets, and fish holds. Adults can easily hitch a ride on the bottom of boat hulls or on barges.

Fisheries experts have set up two experimental projects to relocate vanishing native mussel species to parts of the Upper Mississippi River with lower zebra mussel densities.

Benjamin said, "We need to find a place to move enough mussel species out of harm's way so (that) if we ever do get a handle on zebra mussels and how to control them, we have the genetic material to put the ecosystem back together."

Fisheries authorities on the West Coast are alert to the possibility that zebra mussels may have reached the Columbia River. The U.S. Coast Guard and the Fish and Wildlife Service, working closely with the office of U.S. Senator Ron Wyden of Oregon, have released U.S. $275,000 for a three-year study of aquatic nuisance species in the lower Columbia River.

The Columbia River is considered to be at risk for invasion by potentially damaging non-native species such as zebra mussels.

The study will be conducted by the Pacific States Marine Fisheries Commission in collaboration with Portland State University, the University of Washington, and Oregon State University.

Copyright 2001 Environmental News Network

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