Impacts of elevated water carbon dioxide partial pressure at two temperatures on Atlantic salmon ( Salmo salar L.) parr growth and haematology

Abstract

Atlantic salmon ( Salmo salar L.) parr (10–13 g) were exposed to two levels of carbon dioxide partial pressure (0.3–0.5 mm Hg, control group and 12 mm Hg, high group) at two different temperatures (5 °C and 15 °C) for 47 days in an open flow system. Fish density was low in all groups (less than 7–8 kg m − 3 ) and the specific water flow was high (higher than 1 L kg − 1 min − 1 ) to avoid accumulation of other metabolites. Sodium bicarbonate was added to the water with high carbon dioxide concentration, stabilizing the pH in the range 6.4–6.9 for all four groups. Final mean weight, length and condition factor of the high carbon dioxide groups were significantly reduced compared to their respective control group ( p < 0.05). The reduction in specific growth rate was more pronounced at 5 °C than at 15 °C. At 5 °C there was almost no growth at elevated carbon dioxide concentrations, with mean reduction in weight of 80% relative to the control group. The weight reduction caused by high carbon dioxide concentration was much less at 15 °C (approx 30%) even though the oxygen saturation was lowest in this group. Significant gill lesions, mortality and nephrocalcinosis were not detected in any group. Red blood cell count did not differ between the groups. However, erythrocyte volume declined and erythrocyte haemoglobin content increased in fish exposed to high water carbon dioxide levels at low temperature. The present investigation showed that the impact of elevated carbon dioxide was lowest in the high temperature group.