Visual Performance and Ocular System Structure of Kokanee and Sockeye Salmon following Strobe Light Exposure

Abstract

The use of flashing strobe lights to deter salmon from dam intakes and other hazardous underwater structures has become an appealing method for reducing salmon mortalities. However, no research has been carried out to determine how strobe light emission could affect the visual system of salmonid fishes. The present study investigated behavioral and ocular system changes after short-term (1- and 5-min) and long-term (3-h) exposure of kokanee and sockeye salmon (the lacustrine and anadromous forms of Oncorhynchus nerka). The onset of the escape response to an overhead shadow was different between treatments. Fish exposed for 1 or 5 min showed a response within 5 and 25 min of treatment, respectively, whereas the 3-h-exposed sockeye salmon responded a minimum of 64 h postexposure. All the retinas and lenses examined showed the same characteristics regardless of treatment. We conclude from these results that strobe exposure for 1 min or more induces a state of torpor in sockeye salmon, but exposure for no longer than 5 min does not induce permanent damage to the ocular system.