Abundance and Spawning Distribution of Susitna River Chum and Coho Salmon

Uncertainty over the status of the Susitna River chum, Oncorhynchus keta, and coho, O. kisutch salmon stocks prompted the Alaska Department of Fish and Game to estimate the spawning distribution and abundance of these stocks throughout the drainage.  In 2010, four fish wheels at river km 34 were used to capture chum and coho salmon for marking with dart tags and radio tags.  Fish were recaptured at two upstream fish wheels sites, each with two fish wheels.  One recapture site was on the mainstem Susitna 41.5 km upstream of the mouth. The second recapture site was on was the Yentna River, a tributary to the Susitna River, 10 km upstream of its confluence with the Susitna River.

Darroch model abundance estimates for the entire Susitna drainage were 196,417 (95% C.I. 153,498 - 281,020) coho salmon and 356,996 (95% C.I. (284,573 - 476,270) chum salmon.

Radio tagging data indicated chum and coho salmon were strongly bank oriented at the tagging site and spawning habitats were dissimilar.  Approximately 62% of the chum salmon spawned in mainstem sites (including the Susitna, Yentna, and Skwentna rivers), while 42% of the coho salmon used mainstem sites to spawn.   Of the 374 radio tagged chum salmon, 332 (88.5%) were assigned spawning locations.  Of the 344 radio tagged coho salmon, 301 (87.5%) were assigned spawning locations.