The effect of hypercapnia on the metabolism and growth in striped catfish (Pangasianodon hypophthalmus)

Start date: 5 February, 2017 End date: 4 May, 2017 Project type: Master's Thesis (prior to 2018) Project code: A30183 Countries: Vietnam Grant recipient: Tine Haslam Nielsen Total grant: 18,000 DKK



Hypercapnia in aquacultures have been associated with negative effects such as a reduced food consumption, reduced aerobic scope, and reduced growth in several water-breathing species. Though, the effects of hypercapnia on air-breathing fish is limited. In the present study, standard metabolic rate, maximum metabolic rate, and the partitioning of air-breathing in P. hypophthalmus long-term exposure to 3% CO2 and an acute exposure to 3% CO2, were estimated using intermittent closed respirometry combined with a chase protocol. Further, two growth experiments were conducted and blood samples were collected to determine the effects of hypercapnia on haematocrit, plasma pH, and pH regulation. Standard metabolic rate, routine metabolic rate, maximum metabolic rate, and aerobic scope remained unchanged when exposed to hypercapnia. Likewise, no difference in growth was found. The air-breathing was significantly higher for the hypercapnic group measured in hypercapnia with 18.608 ± 2.820%, compared to the normocapnic group measured in normocapnia and the hypercapnic group measured in normocapnia which was 8.902 ± 2.410% and 8.670 ± 2.311% respectively. The bicarbonate level in the hypercapnic group was significantly higher than in the normocapnic group (33.462 mM difference, p: <0.01) and the chloride concentration was equivalent smaller (38.200 mM difference, p: <0.01). There was no difference in pH nor in haematocrit. This suggests that P. hypophthalmus is able to fully compensate the decrease in pH that hypercapnia would cause without any consequences for growth or metabolism, which makes it an excellent fish for aquaculture.