Size, Diet, and Condition of Age-0 Pacific Cod (Gadus macrocephalus) during Warm and Cool Climate States in the Eastern Bering Sea

The revised Oscillating Control Hypothesis for the Bering Sea suggests that groundfish recruitment is linked to climatic processes affecting seasonal sea ice that, in turn, drives the quality and quantity of prey available to fish for growth and energy storage during their critical life history stages.  We test this notion for age-0 (juvenile) Pacific cod (Gadus macrocephalus) by examining the variability in size, diet, and condition (energetic status) during warm (2003 to 2005), average (2006), and cool (2007 to 2011) climate and sea temperature states in the eastern Bering Sea.  Juvenile cod stomachs contained high proportions of age-0 walleye pollock (by wet weight) during warm years with a shift to euphausiids and large copepods during cool years.  Juvenile cod were largest during warm years and smallest during cool years.  However,  the condition of juvenile cod was highest during cool years.  This result is likely linked to the shift to lipid rich prey found in greater abundance on the shelf and in the stomach contents of juvenile cod during cool years.  Our results for juvenile cod are coincident with juvenile pollock, suggesting that the common mechanisms regulating gadid recruitment on the eastern Bering Sea shelf are sea temperature, prey quality and quantity, and condition of gadids prior to winter.