Current Status of Accomplishment or Milestone: Manuscript "Coastal Sea Surface Temperature
and Coho Salmon Production Off the Northwest United States" by James Cole has been submitted to
Fisheries Oceanography, and accepted pending revisions.
Background: Coastal ocean conditions play an important role in marine survival of young coho salmon,
hence the number of adults returning to freshwater each year (the Oregon Production Index or OPI).
Upwelling variability during the juvenile coho's first ocean spring and summer may be particularly important in determining adult production.
Purpose of Activity/Goal of Project: Since 1985 there has been a sharp decline in the ocean survival of coho salmon.
The goal of this work was to create a time series of sea surface temperature (SST) from AVHRR imagery, as an index of coastal ocean conditions,
to address these questions: 1) do ocean conditions account for the drop in hatchery-reared coho survival since the mid-1980s;
and 2) can SST data be used to predict coho salmon production on an annual basis for management purposes?
Description of Accomplishment and Significant Results: The relationship between coho survival and SST anomalies calculated weekly
in the region 37-51° N during 1985-1996 was examined using univariate and bivariate regression analysis for a number of different time frames.
The sum of negative SST anomalies from April to June, when juvenile coho first enter the ocean, was highly correlated against survival.
In the bivariate analysis, the second independent variable was the sum of the
positive SST anomalies in January to June of the fishes' second calendar year in the ocean, since winter downwelling has been shown to
influence coho survival. Together these SST variables explain over 90% of interannual variability in the marine survival of hatchery-reared coho salmon from 1985 to 1996.
Significance of Accomplishment (e.g., to the Center, to Management, and to NMFS Strategic plan Goals): The analysis of SST time series may allow
management to make reasonable forecasts of hatchery-reared coho salmon survival.
Problems: None.
Key Contact: Frank Schwing (831-648-9034, fschwing@pfeg.noaa.gov).