Influence of Spring Temperature on Juvenile Sockeye Salmon Distribution, Size, Condition, and Diet Along the Eastern Bering Sea Shelf
In order to determine possible factors influencing early marine growth and survival of juvenile sockeye salmon along the eastern Bering Sea continental shelf, interannual variations in distribution, size, indices of feeding and condition of juvenile Bristol Bay sockeye salmon Oncorhynchus nerka were assessed among fish collected in August – September (2000– 03) during Bering–Aleutian Salmon International Surveys.
Juvenile sockeye salmon were mainly distributed within the southern region of the eastern Bering Sea, south of 57°0'N during 2000 and 2001 and farther offshore, south of 58°0'N during 2002 and 2003. In general, juvenile sockeye salmon were significantly larger (P < 0.05) and had significantly higher indices of condition (P < 0.05) during 2002 and 2003 than during 2000 and 2001. The feeding index was generally higher for age-1.0 sockeye salmon than age 2.0 during all years.
Among-year comparisons suggested that Pacific sand lance (Ammodytes hexapterus) were important components of the juvenile sockeye salmon diet during 2000 and 2001 (20% to 50% of the mean wet mass) and age-0 pollock (Theragra chalcogramma) were important components during 2002 and 2003 (50% to 60% of the mean wet mass). Warmer sea temperatures during spring and summer of 2002 and 2003 likely increased productivity on the eastern Bering Sea shelf, enhancing juvenile sockeye salmon growth.
