They said the spill could mean severe losses to Alaska's fishermen, because in this season pink salmon are migrating from the coast to the ocean and herring are moving in toward the shore.

In June, after the salmon have migrated to the ocean, Metro opens the structure.

About 16 million salmon once migrated from the Pacific each year to spawn in the tributaries along the 1,200 miles of the Columbia, a number that has dwindled to around 700,000.

The type of salmon caught varies with the time of year because not all salmon migrate and spawn at the same time.

The salmon typically migrate from West Coast streams, to the center of the Pacific and then return to the North American streams to spawn.

Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true.

Once, 16 million salmon migrated annually to the Columbia River system.

When juvenile salmon migrate to the Pacific Ocean, the second host releases a stage infective to salmon.

Organic farming as it has been defined for 30 years is a managed system tracking everything that goes into production, but salmon migrate thousands of miles across oceans and their habitats cannot be carefully monitored.

The spill continued for a day, pouring into Carquinez Strait, through which salmon were migrating, and coating the adjoining 100-acre Peyton Marsh.