Variations in growth in haemoglobin genotypes of Atlantic cod (original) (raw)

In the present paper are described the growth properties of three different haemoglobin genotypes of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16°C. In addition one group was reared under ''temperature steps'' i.e. moved successively from 16 to 13 and 10°C. The genotype Hb-I(2/2) displayed the overall highest growth rate in the temperature range 13-16°C, whereas the Hb-I(1/1) genotype showed the highest overall growth at the lowest temperature (7°C). Accordingly, we found a significant interaction between genotype and temperature. The differences in growth were largest when cod were reared under the temperature step regime where the Hb-I(2/2) genotype displayed 17 and 24% higher growth than Hb-I(1/1) and Hb-I(1/2), respectively. Optimal temperature for growth (T opt. G) varied between the genotypes with the genotype Hb-I(1/2) displaying the highest (mean ± SE) T opt. G (14.5 ± 1:0.8°C) and Hb-I(1/1) the lowest (12.5 ± 0.2°C). The biological significance of this link between biochemical genetic variation and physiological properties might be the influences on growth pattern, ultimate size and age at first maturity.