Coastal Coho: what drives their abundance?
Oregon Coast Coho
Coho occur in all Coast Range basins in Oregon. They form the basis of popular freshwater and ocean fisheries. While the adult abundance of coho fluctuates annually, their numbers on the Oregon coast had declined to the point where they were listed under the federal Endangered Species Act in the late 1990’s.
The Road to Recovery
Following listing, there was a significant investment in habitat restoration, a reduction in hatchery coho releases, and curtailment of fisheries. Additionally, ocean conditions improved resulting in higher survival. As a result, the abundance of Oregon Coast Coho has generally increased since the late 1990’s.
What We’re Doing
How much has change in spawner abundance been driven by changing ocean conditions versus improvements in freshwater habitat? To answer this, The REDD group are combining 45 years of abundance data across 18 populations with independent estimates of ocean survival. We are modeling each population’s freshwater productivity with Bayesian hierarchical state-space methods in an attempt to leverage information across populations while also accounting for imperfections in our estimates of adult abundance. The results will help us determine the viability of coastal coho in light of uncertain and uncontrollable ocean conditions.