Salmon Leap

A salmon run is an annual fish migration event where many salmonid species, which are typically hatched in fresh water and live most of their adult life downstream in the ocean, swim back against the stream to the upper reaches of rivers to spawn on the gravel beds of small creeks. After spawning, most Atlantic salmon and all species of Pacific salmon die, and the salmon life cycle starts over again with the new generation of hatchlings. Salmon are anadromous, spending their juvenile life in rivers or lakes, and then migrating out to sea where they spend adult lives and gain most of their body mass. When they reach sexual maturity, the adults return to the upstream rivers to reproduce. Usually they return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetoreception to locate the general position of their natal river, and once close to the river, that they use their sense of smell to home in on the river entrance and even their natal spawning ground. Trout, which are sister species of salmon, also perform similar migrations, although they mostly move potamodromously between creeks and large freshwater lakes, except for some coastal/estuary subspecies such as steelhead and sea trout that migrate seasonally between salty/brackish and fresh water just like salmon do. There are also landlocked populations of some salmon species that have adapted to spend their entire life in freshwater like trout. In Northwest America, salmons are keystone species, which means the ecological impact they have on other wildlife is greater than would be expected in relation to their biomass. Most salmon species migrate during the autumn (September through November), which coincides with the pre-winter activities of many hibernating animals. The annual salmon run can be a major feeding event for predators such as grizzly bears and bald eagles, as well as an…