Effects of hypoxia on the partitioning of oxygen uptake and the rise in metabolism during digestion in the air-breathing fish Channa striata

The air-breathing striped snakehead Channa striata is an important fish in Asian aquaculture with high market value. C. striata is typically cultured in simple mud ponds, where it is frequently exposed to severe hypoxia throughout the growth cycle. Here, the partitioning of oxygen uptake during digestion, and the size of the postprandialmetabolism (specific dynamic action or SDA), were studied in hypoxic and normoxic snakehead (30 and 150 mm Hg, respectively). The ventilatory response to hypoxia was investigated separately. When fish were fed 5% of their body mass as fish fillet, total MO2 increased to 2-2.5 times above the standard metabolic rate. Peak MO2 was significantly lower in hypoxic fish (253 mg O-2 kg(-1) h(-1)) compared to normoxic fish (322 mg O-2 kg(-1) h(-1)), and the total SDA was also significantly lower in hypoxia. These results show that despite C. striata being an air-breather, the limited aquatic respiration in severe hypoxia impairs its general performance during digestion. These results have implications for the aquaculture practices of C. striata, and probably other species within this genus, because increased oxygen availability in the water would be expected to increase their digestion efficiency. Further studies are needed to understand the underlying mechanisms, and to determine optimal aeration in these aquaculture ponds. (C) 2012 Elsevier B.V. All rights reserved.