Response of Juvenile Coho and Chinook Salmon to Strobe and Mercury Vapor Lights

Abstract

Species‐specific responses to flashing (strobe) and nonflashing (mercury vapor) lights were monitored in hatchery‐reared juveniles of coho salmon Oncorhynchus kisutch and chinook salmon O. tshawytscha. Fish behaviors were characterized as attraction and avoidance responses, and as active, passive, and hiding behaviors. We investigated how basic fish behavior and activity changed when fish held under a variety of ambient light conditions were exposed to strobe and mercury light. Implications of how these behaviors may influence migrating smolts at a fish bypass system were discussed. Both chinook and coho salmon avoided strobe and full‐intensity mercury light, but chinook salmon exhibited an attraction to dim mercury light. Coho and chinook salmon showed different behavior patterns under most conditions when exposed to strobe and mercury light: coho salmon hid 47% of the time, whereas chinook salmon swam actively 74% of the time. The greatest change produced by either of the stimulus lights was at night when both species normally were passive; exposure to mercury light at nighttime increased fish activity by 90%. Both species also showed similarities in their levels of excitability (e.g., sudden or explosive movements in otherwise sedentary behaviors). The results of this study showed that the behaviors were reproducible: more than 80% of the fish exhibited the same behavior during specific environmental conditions, and sudden and infrequent behaviors were strongly associated with these behavior categories. The behaviors observed in our experimental environment may give insight as to how changes in light relate to fish behavior in bypass systems.

Characterization of Gatewell Orifice Lighting at the Bonneville Dam Second Powerhouse and Compendium of Research on Light Guidance with Juvenile Salmonids

“…Pink and chum salmon show nocturnal activity and are either negatively phototaxic (Simenstad et al 1999) or positively phototaxic (Hoar et al 1957), depending on the light level. Juvenile coho salmon (74-104 mm) exhibit a strong cover-seeking reaction when exposed to full ambient daylight, while juvenile Chinook salmon (79-115 mm) appear unresponsive to light stimuli (Nemeth and Anderson 1992).…”

“…Small fish avoid lights generally because of predation (Nemeth and Anderson 1992;Tabor et al 2004). Tabor et al (2004) in a series of laboratory and field experiments found downstream migration by sockeye fry was hindered by lights (maximum 10.8 lux), and the fish were then more vulnerable to predation by sculpin.…”

“…The behavioral response of juvenile coho and Chinook salmon to mercury lights was evaluated under different pre-exposure light regimes (Nemeth and Anderson 1992). In these tests, fish were adapted to one of four conditions: normal daylight, normal nighttime, and reversed day and reversed night.…”

Lake Roosevelt Fisheries Evaluation Program, Part C; Lake Roosevelt Pelagic Fish Study: Washington Department of Fish and Wildlife, 1998 Annual Report.

“…Hydroacoustics on dam intakes allows for accurate measurements of total entrainment (Johnson et al 1994;Ransom and Steig 1994). Several strategies to minimize entrainment have been used including strobe lights, sound impulses, and fish capturing devices (Nemeth and Anderson 1992;Ross et al 1993;Knudsen et al 1994). Entrainment is currently being estimated at Grand Coulee Dam with an array of hydroacoustic transducers by the Colville Confederated Tribes (CCT) in corroboration with Biosonics Inc. Entrainment estimates will be particularly useful when compared to pelagic fish abundance estimates from the reservoir.…”

Dworshak Reservoir Kokanee Population Monitoring, Annual Report 2001.

“…Previous studies have achieved good success at affecting the behavior of different species of fish with the use of strobe lights (Patrick 1982;Nemeth and Anderson 1992;Winchell et al 1994;Ploskey and Johnson 2001). Strobe light testing for this project was first conducted offsite in 1997 in Spirit Lake and Lake Pend Oreille and again in 1998 on Lake Pend Oreille.…”