Improving Preseason Forecasts of Sockeye Salmon Runs through Salmon Smolt Monitoring in Kenai River, Alaska: 2005 - 2007

This project estimated the age, size, and stable isotope composition of Kenai River sockeye salmon smolts and estimated their abundance using mark-recapture and acoustic methods in 2005-2007. Mark-recapture estimates of sockeye salmon smolt abundance were 31,297,118 (95% CI:23,528,024-39,066,212) in 2005, 9,279,385 (95% CI: 5,937,420-12,621,349) in 2006, and 9,767,167 (95% CI: 6,898,759-12,635,576) in 2007. Acoustic estimates (day and night) of sockeye salmon smolt abundance were 54,702,090 (95% CI: 53,554,507-55,849,673) in 2005, 15,088,517 (95% CI: 14,548.445-15,628,589) in 2006, and 24,350,888 (no variance estimate) in 2007. Our total (day and night) acoustic sockeye salmon smolt abundance estimates were likely biased high due to noise from entrained air created by boat traffic and perhaps greater schooling of other fish species during the day. Our mark-recapture abundance estimates were likely biased low, because the traps were only operated during the night due to very low catches during the day. Although, the precision of the acoustic abundance estimates was higher than the mark-recapture estimates, we could not conclude that either method was superior, because the estimates provided by both methods appeared to be biased in different ways. Therefore, actual smolt abundance was probably between the total acoustic (day and night) and mark-recapture estimates. Sockeye salmon smolt weight tended to decline as the contribution of marine derived nutrients in smolt tissues increased supporting the conclusion that negative density dependence was the primary mechanism regulating growth. This dataset contains (1) counts of fish by species captured in inclined-plane smolt traps operated on the Kenai River (rkm 71.4), (2) age, weight, length data for sockeye salmon smolt captured in the traps, (3) lengths of fish released and recaptured in dye-marking experiments, (4) stable istope compositions for sockeye salmon smolts, (5) acoustic estimates of smolt abundance, and (6) physical data (water temperature, conductivity, relative depth, Secchi depth). Publications: Willette, T.M. and R.D. DeCino. 2009. Improving Preseason Forecasts of Kenai River Sockeye Salmon Runs through Salmon Smolt Monitoring – Technology Development. Exxon Valdez Oil Spill Gulf Ecosystem Monitoring and Research Project Final Report (Project 050675), Alaska Department of Fish and Game, Commercial Fisheries Division, Anchorage, Alaska.