Catches of Yearling Chinook in June
and Coho in September

Numbers of juvenile salmon caught during our June and September trawl surveys can serve as an index or surrogate measure of ocean survival for spring Chinook and coho salmon.  Figure 36 shows catch per unit effort (CPUE) during our trawl surveys from 1998 to 2010. 

Figure 36.	Average catches of juvenile coho (black bars) and yearling Chinook (red bars) during trawl surveys off the coast of Washington and Oregon. Surveys were conducted in June (upper panel) and September (lower panel) from 1998 to present. Note the difference in the scale of the y-axis between plots.

Catch rates were lowest for both species during 2005, but rebounded gradually from 2006-2008, only to decline again from 2009-present (June).

Figure 37 shows the relationship between catches of juvenile Chinook and coho and returns the following year of coho adults and Chinook jacks.  In the upper panel, trawl catches of coho in September of year i are correlated with adult counts from the Oregon Production Index of hatchery coho adult returns (OPIH in year i + 1).  Similarly, catches of yearling Chinook in June of year i are correlated with counts of spring Chinook jacks at Bonneville Dam in year i + 1. 

Figure 37.	Upper panel shows regression of the OPIH smolt-to-adult survival (SAR) of coho salmon on the average CPUE of juvenile coho salmon catches in trawl surveys the previous September. Years indicated are for catches of juvenile fish. The purple open circles indicate observed juvenile CPUE in September 2010 (0.03) and predicted SAR from jack returns (1.9%) and from our September 2010 catch (2.3%). Black open circle indicates observed juvenile CPUE (0.30) in September 2011 and predicted SAR (2.8%)
	Lower panel shows regression of spring Chinook salmon jack counts at Bonneville Dam (1998-2011) vs. average CPUE of yearling Chinook salmon caught during each June cruise. Open black circle indicates observed CPUE in June 2011 (0.46) and predicted jacks from the regression (8,187). The year 2010 (circled) was excluded from the regression.