Atlantic cod (Gadus morhua) from cold and warm environments differ in their maximum growth capacity at low temperatures

Abstract

Maximum growth rate of Atlantic cod (Gadus morhua) was determined at a range of temperatures representative of cod benthic habitats (1–13 °C) using wild animals obtained from a cold environment (southern Gulf of St. Lawrence stock, SG) and a mild environment (Bay of Fundy stock, BF). SG cod performed well over a broader range of temperatures than BF cod. Growth in mass was greater for SG than BF cod at any temperature below 7 °C. SG cod consumed twice as much food as BF cod at 1 and 3 °C. At 1 °C, growth in mass was positive for SG cod but negative for BF cod, whereas growth in length did not differ from 0 for both SG and BF cod. Liver size represented a larger proportion of body mass in SG cod at both low and high temperatures, and citrate synthase activity in the intestine exhibited a strong inverse relationship to temperature. The maximum growth capacity of SG cod was comparable with that of cod of similar size in various other stocks in the Atlantic. These observations are not consistent with the view that intensive size-selective fishing practices have resulted in a significant loss of innate growth capacity in SG cod.