Salmon spend most of their lives in the ocean, so the conditions they encounter there have a far-reaching effect on their survival. In particular, scientists have observed that cyclic variations in the survival of salmon in the ocean often correspond with ocean temperature changes.  Cold ocean temperatures are not only good for salmon, they are important for much of the plant and animal life in the ocean that salmon rely on for food. 

Climate and its impact on ocean currents and temperatures is so important to salmon survival, particularly during their vulnerable first year in the ocean, that scientists can predict adult salmon returns to the Columbia River based on the ocean conditions the year they migrated out to sea.  And, in fact, the listing of several salmon stocks as threatened or endangered under the ESA coincides with a prolonged period of poor ocean conditions that began in the early 1990s.