-Large numbers of spiny dogfishSqualus acanthiasmoved into the area near the mouth of the Big Qualicum River, British Columbia, at the time hatchery-reared smolts of Chinook salmonOncorhynchus tshawytschaand coho salmonO. kisutchwere leaving the river in 1988 and 1989. A small percentage of the spiny dogfish preyed on the smolts, but the resulting smolt mortality is believed to have been large because of the large numbers of spiny dogfish in this area. Spiny dogfish also fed on adult salmon in the fall. The long-term decline in survival of chinook salmon produced at the Big Qualicum Hatchery was similar to the pattern of survival of other hatchery-produced salmon. We propose that this long-term decline in survival results from predation.