Long-term changes in growth of North-east Arctic cod (Gadus morhua) and some environmental influences

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Abstract
An analysis of the growth of immature North-east Arctic cod in the period 1953 to 1989 is presented. The paper addresses in particular the long-term changes and attempts to relate these to variations in the ratio of capelin to cod stock abundance (an index of food availability) and temperature fluctuations. No sex differences in growth were observed, and growth was effectively linear over the age range studied (1–8 years). Marked shortterm (1–5 years) variation in length-at-age was observed, but no overall trend was detected. The amplitude of the short-term variations was of the order 10–15 cm. Growth in length of cod was found to be positively related to increasing ratio of capelin to cod stock abundance and also to increasing water temperature. A sharp reduction in lengthat-age and also a decline in the condition factor by 20% was observed between 1984 and 1988, reducing weight-at-age by up to 60%. This change may have been a direct consequence of the dramatic decline of the capelin stock in 1985/1986. Clear geographical differences in length-at-age of cod were observed within the Barents Sea. The estimation of mean size-at-age is therefore critically dependent on the sampling strategy.

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