Biochemical composition and calorie content of pollock <i>Theragra chalcogramm</i>a in the Okhotsk Sea

Walleye pollock tissues include 18.5 % of dry matter, on average. Lipids are 0.7 % of the pollock wet weight, proteins - 15.3 %, carbohydrates - 0.6 %, and ash - 1.3 %. Mean calorie content of its tissues is 940 cal/g for the raw material and 5080 cal/g for the dry matter. Portion of dry matter in its gonads is 14.9-28.0 % for females and 14.5-17.0 % for males; lipids content in the gonads is 0.9-3.0/1.3-1.8 % for females/males and proteins content is 10.7-13.4/10.2-21.5 %, respectively; calorie content of the gonads is 702-1537/4426-5482 cal/g for the raw/dry matter of females and 760-960/4952-5641 cal/g for the raw/dry matter of males. The pollock liver contains 42.2-62.2/34.4-62.4 % of dry matter for females/males, including 25.6-44.5/16.6-41.3 % of lipids and 6.3-9.8/8.1-12.3 % of proteins, respectively, with calorie content 2918-4601/6370-7395 cal/g for the raw/dry matter of females and 2291-4357/6392-7492 cal/g for the raw/dry matter of males. The calorie content of the liver tissue is much lower for the juveniles: 963/2045 cal/g for the raw/dry matter. The pollock faeces contain 15.0-18.4 % of dry matter, in dependence on the fish size, including 1.1-1.6 % of lipids, 1.8-3.8 % of proteins, and 0.9-1.4 % of carbohydrates; their calorie content is rather stable for the raw material (308-362 cal/g) but the calorie content of the dry faecal matter depends strongly on the fish size and varies from 259 to 2377 cal/g. The muscle tissue of pollock accumulates 56.5-93.9 % of the total energy content of its body, the gonads - 0.9-26.6 % for females and 0.4-7.3 % for males, the liver - 7.9-27.2 % for females and 5.7-26.9 % for males, i.e. energy accumulation in gonads and liver of females is higher than in these organs of males. Maximum loss of energy (15-30 %) is observed during the spawning, on the transition from stage 5 to stage 6 of maturity. The total accumulated energy during the pollock growth from juvenile fish (< 17 cm) to super-large size (> 60 cm) is on average 1964 kcal for females and 1465 kcal for males, the difference is caused by higher energy needs for oogenesis, as compared with spermatogenesis.