2018 Coho Spawning Runs Larger Than Expected

Adult female coho salmon spawner in Redwood Creek.

NPS / Jessica Weinberg McClosky

March 2018 - Early January finally saw enough rainfall for adult coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) to reach their stream spawning habitats. Despite this long wait, the coho and steelhead spawning run in both Olema and Redwood Creeks was larger than anticipated, even when factoring out the addition of hatchery-released coho in Redwood Creek.

Preliminary totals for the coho spawning season include 83 adult coho on Olema Creek, but only 12 redds. Likewise for Redwood Creek, redd production was low when compared to the number of wild coho observed (4 redds to 18 wild coho).

This may have been due to the higher number of “jacks” (fish that only spend 6 months in the ocean versus the typical 18 months) seen this year. In Olema Creek, 55% of the live coho observations were jacks, and at least 33% of the wild adult coho observed on Redwood Creek were jacks. In one case, a female and 11 males were seen on a redd, and most of the males were jacks competing for a chance to spawn with the lone female. However, the total redd count was high (81) when those produced by the released hatchery-reared coho were included.

Although the steelhead spawning season is still underway, it seems to be average for Redwood and Olema Creeks but below average for Pine Gulch Creek. With two months left to go, though, it is too early to draw any conclusions. Learn more about 2017-2018 spawner survey results here.