Salmon and steelhead are anadromous fish.  They are born and rear in fresh water, migrate downstream through the Columbia River and its tributaries, including the Snake River, to the Pacific Ocean where they grow and live as adults, returning to their natal streams and lakes to spawn and die. 

The Columbia River basin historically provided habitat for chinook, sockeye, chum, and coho salmon, as well as steelhead.  A century ago, between 10 and 16 million salmon returned to the Columbia each year.  As of 1991, 67 stocks of Columbia River salmonids were extinct and 76 stocks were at risk of extinction.

Hydropower dams are the principal cause of the decline in salmon and steelhead, particularly by creating large slackwater pools that kill large numbers of migrating juvenile fish.  In addition, degradation of spawning and rearing habitats -- from grazing, logging, roads, irrigation diversions, and other human impacts -- causes further mortality and reduces reproductive success.

Preserving salmon and steelhead will require breaching four dams on the lower Snake River -- which provide limited amounts of energy -- plus restoring headwaters habitats, particularly on public lands in Idaho and the Northwest.