Observations of Repeat Spawning of Steelhead in Yakutat Alaska

Since 1995, a bipod and picket weir with a resistance board section was used to count steelhead kelts emigrating from the Situk River in Southeast Alaska. Counts averaged 9,259 and ranged from 5,335 to 15,003 for the decade ending in 2010. Mean length of kelts did not decline in samples taken during this time period. Males averaged 763 mm (SE = 8) and females 773 mm (SE = 7). The sex ratio of kelts sampled at the weir was skewed to females, but male fish made up the majority of fish that were found dead and washed up on the weir. The repeat spawning rate, as measured with PIT-tagged fish, was 9% for fish that returned a second time, and 1% for fish that returned a third. PIT-tagged fish that were recaptured multiple times showed considerable consistency in date of emigration across years (mean = 9 days). Run timing of the emigration varied with midpoint dates that ranged from May 18 to June 14. Emigration timing appeared to be triggered by water temperatures above 6°C. Kelt abundance the following year was positively correlated to the previous year’s water temperature in May. The sport catch during the study years averaged 12,118 and did not track the abundance trend of kelts. The sport harvest of steelhead, which was restricted to trophy-length fish (>36 inches or 914 mm TL) and limited to 2 per year, averaged 26 fish. The average percentage of trophy-length fish in a weir site sample was 3%. The largest fish sampled was 1,100 mm and the smallest was 400 mm. Other comparitive studies of steelhead in Southeast Alaska have reported higher return rates. The Situk River is the longest stealhead bearing river system in Southeast Alaska that is studied, which may partially account for the observation of lower return rates when compared to the typically short river sytems found throughout Southeast Alaska.