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This paper summarizes an investigation of food intake and its effect on growth, conversion efficiency, and condition factor of juvenile walleye pollock (Theragra chalcogramma) maintained in captivity in Seward, Alaska. Observations were made at 3 to 7–5°C, the range pollock inhabit in the Bering Sea for most of the year. Food consumption was measured as weight eaten in percentage of body weight per day and also in calories per day.Maximum food consumption (% b.w./day) and maximum growth (weight gain as a % b.w./day) were both negative exponential functions of pollock weight and inverse linear functions of pollock length. Maximum consumption in calories per day was a negative exponential function of pollock weight.In 30–60 g pollock, growth was a linear function of food consumed whether consumption is expressed as % b.w./day or as calories per day. Maximum growth at 3 and 7·5°C was 0·93 % and 2·12 % of body weight per day, respectively. Maintenance ration in this size range was 225 calories per day or 0·26 % b.w./day at 3°C and 382 calories per day or 0·30% b.w./day at 7·5°C. Change in condition factor was a direct, linear function of food intake (r<sup>2</sup> = 0·97 at 3°C; r<sup>2</sup> = 0·87 at 7·5°C), making it possible to calculate the ration required to maintain a constant condition factor. Those required rations are three to four times higher than maintenance rations, suggesting that juveniles, in contrast to adults, preferentially grow in length at low levels of food consumption.During starvation, pollock lose weight at a constant rate (—0·34% of body weight per day at 8°C) and, therefore, condition factor declines linearly with the duration of starvation. Death of juveniles due to starvation occurs at a condition factor of about 0·44.Between 3 and 7·5°C, both maximum food intake and growth were linearly related to temperature. Maximum conversion efficiency was an inverse, linear function of temperature (90 % at 3°C; 37 % at 7·5°C), suggesting that at low levels of food availability, growth is more rapid at colder temperatures. These last results are discussed in relation to the movement by juvenile pollock into colder water during the spring in the Bering Sea. |
