Dams may also modify salmon habitat in more subtle ways.

A、The decline accelerated in the 1970s and by the 1990s the US Endangered Species Act listed 26 kinds of salmon as endangered.;
B、Historically, the upper Snake River produced some 25,000 to 30,000 chinook salmon that spawned during the early fall. The completion of the dam in the late 1950s not only rendered the vast majority of their habitat inaccessible, but also led to more extreme water temperatures downstream from the dam.;
C、Salmon usually spend their entire ocean residence on the continental shelf and return to their natal streams immediately before spawning.;
D、The life cycle of a typical salmon begins with females depositing eggs in nests, or redds, on the gravel bottoms of rivers and lakes.