Fish assemblages are an important component of aquatic ecosystems of the Willamette River. Fish assemblages are recognized as sensitive indicators of habitat degradation, environmental contamination, and overall ecosystem productivity. Seven of the 35 native fish species that commonly occur in the mainstem Willamette River are listed as endangered, threatened, or sensitive by federal or state government, including spring Chinook salmon and winter steelhead.
This indicator measures the number of native fish species present in the river.