Effectiveness of strobe lights for reducing juvenile salmonid entrainment into a navigation lock

Publication Date



chinook, coho, culverts, entrainment, entrance, hydroacoustics, juvenile, ocean, Oncorhynchus tshawytscha, salmon, salmonids, sockeye salmon, steelhead, strobe light, survival

Journal or Book Title

North American Journal of Fisheries Management


Strobe lights effectively reduced fish entrainment into the large locks at the Hiram M. Chittenden Locks Project in Seattle, Washington. The anadromous salmonids of the Lake Washington system, Chinook salmon Oncorhynchus tshawytscha, coho salmon O. kisutch, sockeye salmon O. nerka, and steelhead O. inykiss, must pass through these locks en route to the Pacific Ocean. Of the available downstream passage routes, use of the large lock-filling culverts is considered the most harmful to fish because of potential entrainment contact with the barnacle-lined culvert walls. We evaluated the effectiveness of strobe lights for displacing fish from in front of the culverts and for reducing entrainment during large lock fills. From 3 May to 14 June 2002, we used split-beam hydroacoustics to estimate the number of fish entrained during paired light-on-light-off treatments. Results indicated that strobe lights significantly reduced (75%) entrainment, an estimated 1,427 fish being entrained during lights-off treatments versus 350 during lights-on. Effectiveness was also supported by t-tests on individual range strata in front of the culvert entrances: 1-m strata from the floor to 4 in above the floor indicated significant reduction in number of entrained fish during the lights-on treatments. Using strobe lights for reducing culvert entrainment probably increases juvenile salmonid survival through the locks







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