Seasonal Changes in Whole-body Energy Content and Estimated Consumption Rates of Age 0 Walleye Pollock from Prince William Sound, Alaska

Abstract

This study examined the somatic energy content and prey consumption needs of recruiting walleye pollockTheragra chalcogrammain one of Alaska's large estuaries to begin to evaluate the role of this species in the food-web. Age 0 pollock were collected from Prince William Sound in the fall and spring during 2 years. In the fall of 1995, few recruits <70mm standard length (SL) were present and the mean whole-body energy content (WBEC) was 3·6 (±0·2) kJg−1wet wt. In the following spring the 1995 year class survivors were ≥80mm SL and the mean WBEC was 4·0kJg−1(±0·5). In the fall of 1996 the age 0 pollock had an average WBEC of 3·6kJg−1(±0·2), identical to 1995, but smaller 60–70mm fish were common. In the spring of 1997 few fish <70mm were captured and WBEC averaged 3·4kJg−1(±0·4). In both years, recruits were generally able to maintain or improve their WBEC over the winter. There was marked variation in WBEC for fish from different collection sites.Changes in WBEC of the 1996 year class was monitored during their first year. On 13 June recently metamorphosed pollock had a SL of 34 (±5) mm and a mean WBEC of 2·7 (±0·2) kJg−1vs81 (±10) mm and 3·6 (±0·2) kJg−1on 6 October. Based on these mean values, growth rates for age 0 pollock during their first 119 days were 0·4mmday−1and 7·8Jg−1day−1. Modeling changes in body weight, energy content and metabolic demands for both active metabolism and growth allowed prediction of food intake over their first 270 days. Predicted wet wt of fish increased from an initial 0·37g to a high of 7·6g. Estimated food intake ranged from 0·21 to 1·29kJday−1.