That helps assure a good mix of genetics and a robust fish population. Finding spawning habitat may not be the only need to move about. In small streams, fish find refuge in deep pools to ride out the winter. Getting to the same pools may mean the difference of surviving a summer when flows drop and temperatures climb. Without the access to necessary habitat, fish populations may suffer.
Mobility is everything.
The service's Arizona Fishery Resources Office is similarly engaged. But a low-head dam that delivered irrigation water also blocked fish movement. The White Mountain Apache Tribe and Arizona Fishery Resources Office redesigned the dam to continue delivering irrigation water. Flows are now concentrated midstream over a natural bottom that easily passes fish. But even small structures if not properly placed can have big consequences on fish populations.