South Fork Swim Hole: A half-mile of river runs through it: Anadromous fishes (salmon, steelhead 
  and cutthroat trout) use deep pools like these and nearby riffles with clean 
  gravel to spawn (lay and fertilize eggs). The South Fork parcel and its half-mile 
  of riverfront old-growth, is at left.
http://www.smithriverproject.org/why.shtml