Temperature- and size-dependent growth of larval and early juvenile Atlantic cod (Gadus morhua): a comparative study of Norwegian coastal cod and northeast Arctic cod

摘要

Norwegian coastal (NC) and northeast Arctic (NA) Atlantic cod, G. morhua, larvae were reared on live zooplankton to investigate temperature- and size-specific growth. Larval and juvenile growth was temperature and size dependent. Growth in length and weight increased with increasing temperature from 4 to 14oC, with a corresponding reduced larval stage duration. Maximum growth rate occurred at a larval size of 0.1-1.0 mg dry weight, followed by a declining trend during the juvenile stage. The temperature optimum of larval cod fed in excess is estimated to be between 14 and 16degreeC, with a maximum weight-specific growth potential exceeding 25% day-1. Temperature- and stock-specific growth curves of dry weight at age are well described by a generalized Gompertz model. A stock-specific difference in mean weight at age was observed, with NC growing better than NA. Neither countergradient latitudinal variation in growth capacity of the two larval cod stocks nor temperature adaptation across latitudes was indicated. A stock-specific difference in weight at length was observed in early juveniles, with NC being heavier than NA. Overall, a positive correlation between temperature and condition level was found. No distinct temperature- or stock-specific differences in survival were observed.