Catches of Yearling Chinook in June
and Coho in September
The number of juvenile salmon caught during trawl surveys can serve as an index of the survival for both spring Chinook and coho salmon. Catches of juvenile fish from our trawl surveys are shown in Figure 21.
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| Figure 21. |
Average catches of juvenile coho (black bars) and spring 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 2006. |
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Figure 22 shows correlations between catches of yearling spring Chinook salmon in June and spring Chinook jack returns one year later. Also shown are correlations between catches of yearling coho salmon in September and adult returns the following year. Catches of both juvenile coho and spring Chinook were the lowest of our study, which began in 1998. This suggests that we should anticipate low returns of coho in 2006 (~1.5%) and low returns of spring Chinook salmon in 2007. Returns of coho should be somewhat higher in 2007; returns of spring Chinook in 2007 should be far higher, near the long–term average.
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Figure 22. |
(Upper panel) Regression of OPIH adult coho salmon abundance vs. average CPUE of juvenile coho salmon the previous September. Filled circles show catches of juvenile fish in previous years. Adult production from the 2007 smolt year is a prediction based on jack returns. The open circle indicates CPUE observed in September 2007 (0.14) and predicted OPIH from the regression (432,000).
(Lower panel) Regression of spring Chinook salmon jack counts at Bonneville Dam (1998–2006) vs. average CPUE of yearling Chinook salmon caught during each June cruise. The open point indicates observed CPUE in June 2007 (0.87) vs. predicted OPIH (17,082). |
Catches of both coho and Chinook in 2005 were the lowest of our study, which began in 1998. This suggests that we should anticipate low returns of coho in 2006 (~1.5%) and low returns of spring Chinook in 2007 (below average counts at Bonneville).
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