Postprandial oxygen consumption, ammonia excretion and carbon dioxide production of channel and blue catfish.

Fishes undergo dramatic physiological changes upon consumption of a meal, including an increase in oxygen consumption to support the metabolic cost of digestion [specific dynamic action (SDA)] and an increase in the excretion of ammonia. Channel catfish (Ictalurus punctatus) and blue catfish (I. furcatus) are two species commonly used for commercial aquaculture production in the United States. Postprandial ammonia excretion and oxygen consumption of both channel and blue catfish were measured at 25 and 32°C. Rates of both ammonia excretion and oxygen consumption increased quickly after feeding and were significantly higher within 2 h postfeeding. Ammonia excretion of channel catfish peaked 6 h postfeeding at both 25 and 32°C, with peak ammonia excretion rates increasing 8.3- and 4.7-fold higher than fasting rates at 25 and 32°C, respectively. Ammonia excretion of blue catfish at 25°C peaked 6.6-fold higher than fasting rates at 12 h postfeeding and 5.5-fold higher than fasting rates 6 h postfeeding at 32°C. Relative to fasting levels, postprandial oxygen consumption of channel catfish peaked 1.8- and 2.0-fold higher at 25 and 32°C, respectively. Blue catfish oxygen consumption peaked 1.9- and 1.8-fold higher at 25 and 32°C, respectively. Both channel and blue catfish rapidly increase ammonia excretion and oxygen consumption in response to feeding, with temperature mostly affecting changes in peak and minimum rates.