Acidification severely suppresses spawning of hime salmon (land-locked sockeye salmon, Oncorhynchus nerka)

A laboratory study was conducted to investigate the effects of an acidic environment on the female sexual behavior of hime salmon (land-locked sockeye salmon, Oncorhynchus nerka). Spawning hime salmon were extremely sensitive to the acidity of ambient water. Nest-digging behavior was severely inhibited (P < 0.05) by very slight acidification (pH below 6.4) of the water. Below pH 6.0, females showed almost no diggings. When the ambient water was returned to nearly neutral (pH 6.6), diggings reappeared in four of the six fish tested, whereas in two individuals, none was observed. Avoidance of slightly acidic water in selection of spawning site or cessation of spawning behavior in weakly acidic environments maybe the most potent cause Bf the reduction of salmonid populations in the early stages of acidification. (C) 2000 Elsevier Science B.V. All rights reserved.