Estuaries are partially enclosed bodies of water where rivers and ocean meet.  The combination of salty ocean water and freshwater combine to create one of the most productive ecosystems in the world, and the 250-acre Mattole estuary is no exception.  More than 13 species of fish, 26 species of mammals, and 194 species of birds live in the Mattole estuary alone. Included in this list are the Mattole's 3 federally listed salmonids: coho and Chinook salmon and steelhead.  The estuary is the gateway through which all of salmonids must pass to gain entry into the Mattole River system, and therefore the health of the estuary is critical to the health of our entire salmonid population.