Escapement Monitoring of Adult Chinook Salmon in the Secesh River and Lake Creek, Idaho, 1999 Annual Report.

Abstract

Underwater time-lapse video technology was used to monitor adult spring and summer chinook salmon abundance in spawning areas in Lake Creek and the Secesh River, Idaho, in 1999. This technique is a passive methodology that does not trap or handle this Endangered Species Act listed species. This was the third year of testing the remote application of this methodology in the Secesh River drainage. Secesh River chinook salmon represent a wild salmon spawning aggregate that has not been directly supplemented with hatchery fish. Adult chinook salmon spawner abundance was estimated in Lake Creek with the remote time-lapse video application. Adult spawner escapement into Lake Creek in 1999 was 67 salmon. Significant upstream and downstream spawner movement affected the ability to determine the number of fish that contributed to the spawning population. The first passage on Lake Creek was recorded on July 11, two days after installation of the fish counting station. Peak net upstream adult movement occurred at the Lake Creek site on July 20, peak of total movement activity was August 19 with the last fish observed on August 26. A minimum of 133 adult chinook salmon migrated upstream past the Secesh River fish counting station to spawning areas in the Secesh River drainage. The first upstream migrating adult chinook salmon passed the Secesh River site prior to the July 15 installation of the fish counting station. Peak net upstream adult movement at the Secesh River site occurred July 19, peak of total movement was August 15, 17 and 18 and the last fish passed on September 10. Migrating salmon in the Secesh River and Lake Creek exhibited two behaviorally distinct segments of fish movement. Mainly upstream only, movement characterized the first segment. The second segment consisted of upstream and downstream movement with very little net upstream movement. Estimated abundance was compared to single and multiple-pass redd count surveys within the drainage. There were differences between the two methodologies. The fish counting stations did not impede salmon movements, nor was spawning displaced downstream. Fish moved freely upstream and downstream through the fish counting structures. Fish movement was greatest between the period of 10:00 p. m. and 4:00 a. m. There appeared to be a segment of ''nomadic'' males that moved into and out of the spawning area, apparently seeking other mates to spawn with. This methodology has the potential to provide more consistent and accurate salmon spawner abundance information than single-pass and multiple-pass spawning ground surveys. Accurate adult escapement information would allow managers to determine if recovery actions benefited listed chinook salmon in tributary streams.