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Resource Ecology and Ecosystem Modeling Program

Diet Composition of Walleye Pollock in the Eastern Bering Sea, 1987-2011, and Predator-Prey Relationships with Copepods and Euphausiids - Figures 1, 2, and 3

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Figure 1.  An index of partial fullness of major components in the diet of EBS pollock from 1987 through 2011.  The average index for copepods (Avg cop) and euphausiids (Avg euph) are indicated for 3 periods; 1987-92, 1993-2004 and 2005-11.

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Figure 2.  The trend in the average annual weight composition (%W) of copepods (upper panel) and euphausiids (lower panel) relative to the average annual stomach fullness (%bw) of each size category of pollock sampled by AFSC’s EBS bottom trawl survey, 1987-2011.  Correlations are significantly (P < 0.05, thick solid line), almost significantly (0.10 > P > 0.05, thick dashed line), or not significantly (P > 0.10, thin dashed line) different from zero. 


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Figure 3.  Time series of euphausiid biomass from the hydroacoustic survey and the combined %W of euphausiids and hyperiid amphipods in the diets ofsix sizes of pollock from the Bottom Trawl Survey. The seven time series are normalized to their 2004 value to indicate the relative change over time.  Euphausiid biomass data courtesy of P.H. Ressler. 




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