1.   The mussels are found only in fastflowing freshwater rivers which are largely free of pollution.

2.   It will become a freshwater river permanently at its present high-water mark.

3.   Above the federal dam at Troy, N.Y., the Hudson is a purely freshwater river.

4.   President Clinton has also ordered the agency to come up with new offshore ocean water-quality standards, similar to those that govern freshwater rivers and lakes.

5.   They are highly migratory, meaning they are born in freshwater rivers and streams, then head to the ocean for two or three years before returning to spawn.

6.   They can live in the sea, tidal rivers or completely freshwater rivers, swamps and billabongs.