Asian clams, foreign troublemakers in waters throughout 39 states, have turned up at the federal Gavins Point National Fish Hatchery at Lewis and Clark Lake in eastern South Dakota.

Officials said the clams do not directly threaten the health of such endangered species as the pallid sturgeon raised at the hatchery. The trouble the clams cause shows later as they rapidly reproduce, consuming large quantities of food and displace native species, altering the food chain.

The clams also can plug water pipes.

The U.S. Fish and Wildlife Service said it was reviewing the hatchery's operating measures to prevent the spread of the invasive species.