<P> Salmon not killed by other means show greatly accelerated deterioration (phenoptosis, or "programmed aging") at the end of their lives . Their bodies rapidly deteriorate right after they spawn as a result of the release of massive amounts of corticosteroids . </P> <P> In the Pacific Northwest and Alaska, salmon are keystone species, supporting wildlife such as birds, bears and otters . The bodies of salmon represent a transfer of nutrients from the ocean, rich in nitrogen, sulfur, carbon and phosphorus, to the forest ecosystem . </P> <P> Grizzly bears function as ecosystem engineers, capturing salmon and carrying them into adjacent wooded areas . There they deposit nutrient - rich urine and feces and partially eaten carcasses . Bears are estimated to leave up to half the salmon they harvest on the forest floor, in densities that can reach 4,000 kilograms per hectare, providing as much as 24% of the total nitrogen available to the riparian woodlands . The foliage of spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from fished salmon . </P> <P> Beavers also function as ecosystem engineers; in the process of clear - cutting and damming, beavers alter their ecosystems extensively . Beaver ponds can provide critical habitat for juvenile salmon . An example of this was seen in the years following 1818 in the Columbia River Basin . In 1818, the British government made an agreement with the U.S. government to allow U.S. citizens access to the Columbia catchment (see Treaty of 1818). At the time, the Hudson's Bay Company sent word to trappers to extirpate all furbearers from the area in an effort to make the area less attractive to U.S. fur traders . In response to the elimination of beavers from large parts of the river system, salmon runs plummeted, even in the absence of many of the factors usually associated with the demise of salmon runs . Salmon recruitment can be affected by beavers' dams because dams can: </P>

Difference between salmon fish and indian salmon fish