When it is time for the salmon to reproduce, the fish uses a remarkable homing ability to find its way back to the river where it was born to spawn and die. This cycle of life and death has gone on for millennia. The Risk Salmon populations have been reduced over the years by habitat loss, over-fishing, and the construction of four dams on the Lower Columbia River. Young fish used to migrate to the Pacific Ocean in the Snake River's cool, free-flowing current. Today, they must struggle through the enormous reservoirs behind the dams, where they are exposed to predators, disease and lethally high water temperatures.
Many fish die when forced through the dams' hydropower turbines.
Costly efforts to collect the young fish with giant screens at the dams and transport them to the ocean by barge have failed to stop the decline. The Corps recently conceded that fish barging would not lead to salmon recovery. The dams also take a heavy toll on adult salmon returning upstream to spawn. Many salmon have trouble finding the fish ladders on the dams. Scientists believe that many of the adults that do eventually reach their spawning grounds upstream are often too exhausted from the grueling journey to spawn successfully.