Anadromous salmonid passage and video image quality under infrared and visible light at Prosser Dam, Yakima River, Washington
video, illumination, delay time, chinook, salmon, coho, steelhead, rainbow trout, trout, fish ladder, spawning, migratory fish, infrared light, night, upstream, salmonids, anadromous fish, fish passage
Journal or Book Title
North American Journal of Fisheries Management
The effect of infrared (>880 nm) and visible (400-700nm) illumination was compared todetermine delay rates (percent of population) and delay times (min) of migratory Chinooksalmon (Onchorhynchus tshawytscha), coho salmon (O. kisutch), and steelhead anadromousrainbow trout (O. mykiss) in the fish ladder viewing chamber at Prosser Dam during the fall 1996spawning season. Overall, a significantly (P < 0.05) greater proportion of migratory fish weredelayed under visible (41%) than infrared illumination (28%). Species-specific comparisonsindicated that significantly (P < 0.05) greater numbers of Chinook and coho salmon were delayedunder visible (57% and 33%, respectively) than infrared (25% and 12%, respectively) lighting. Nosignificant difference was detected in the proportion of steelhead delayed under visible (35%) andinfrared (25%). Passage rates for Chinook salmon under infrared light were significantly (P <0.001, chi square = 10.12) greater at night (70%) than day (30%), whereas under visible lightnearly equal numbers of fish moved upstream during day and night (51% and 49%, respectively).Migrating Chinook salmon readily passed through nonintrusive infrared but not visible light atnight. Diel passage rates for coho salmon and steelhead were similar under infrared and visiblelight. Mean delay times for anadromous salmonids were short (<9 min) and similar in infrared andvisible light. Infrared light facilitated anadromous fish passage at night but compromised videoimage quality and the ability to identify fish species and detect fin clips.