The Salmon’s Sad Fate

The effects of temperature change on creatures at the base of the food chain has ramifications for those higher up both in and outside the water, such as larger filter feeders, perch, trout, salmon, birds, and a large variety of mammals. Salmon runs provide a major source of protein for black and grizzly bears. Plummeting salmon populations often force bears to look elsewhere for food. In the Puget Sound area, the number of bear sightings in suburban neighborhoods is increasing. In parts of the Northwest where grizzly populations are prevalent, human attacks are on the rise. Talk show host David Letterman’s country home in Choteau, Montana, was invaded by an unwelcome grizzly prowler in 2003. Fortunately, no one was at home at the time (Hanson 2004).

There are seven species of salmon in the Puget Sound. Most are in precipitous decline. Salmon populations most affected by increasing temperatures live in stream and estuarine habitats. A combination of increased flooding, lower summer and fall stream flows, and higher temperatures increases their susceptibility to disease and disrupts their reproductive cycles. Most salmon species are vulnerable when water temperatures rise above 70˚F. Since 1974, temperatures in the main migratory route used by salmon moving from Lake Washington to the Puget Sound have risen. The number of days during which summer temperatures rose above 70˚F in this waterway has almost doubled (Puget Sound Action Team 2005). These temperature changes are responsible for up to 50% death rates for migratory species.