First-Year Energy Storage Patterns of Pacific Herring and Walleye Pollock: Insight into Competitor Strategies

Abstract

Changes in length and whole body energy content for Pacific herring and walleye pollock from Prince William Sound, Alaska, were monitored in 1996 to describe growth patterns of these two pelagic competitors during their first year. Metamorphosed walleye pollock were first captured in June, when they averaged 34 mm in standard length (SL) and their whole body energy content (WBEC) was 2.7 kJ/g wet wt. In August they had grown to 69 mm and 3.4 kJ/g wet wt. In October they averaged 81 mm and 3.6 kJ/g wet wt. Metamorphosed Pacific herring were first captured in July, and averaged 28 mm and 2.5 kJ/g wet wt. In August they had grown to 38 mm and 3.1 kJ/g wet wt. In October they averaged 75 mm and 5.0 kJ/g wet wt. Walleye pollock metamorphosed earlier than Pacific herring and in August and October they were on average 31 mm and 6 mm longer than their herring competitors. In August the WBEC of the two species was similar. In October the herring had stored on average ≈1.4 kJ/g more energy than pollock to enter the overwinter period. The survival strategy for first year pollock includes an early metamorphosis followed by rapid growth in length. For herring, metamorphosing later when conditions are warmer and storing more somatic energy for overwintering appear to be primary tactics.