Water temperature is a key physiological regulator of ectothermic organisms. Temperature is closely related to aerobic capacity and blood-oxygen affinity. Because little is known about the aerobic capacity and blood-oxygen affinity of juvenile channel (Ictalurus punctatus), blue (I. furcatus) and hybrid catfish (I. punctatus X I. furcatus) related to high seasonal temperatures, the effects of water temperature on standard and active metabolic rates, swimming performance, and blood-oxygen affinity were evaluated.
Fish were acclimated to either 23 or 33°C in separate recirculating aquaculture systems. Standard metabolic rate (MO2min) was measured using intermittent respirometry and active metabolic rate (MO2max) was measured using a swim flume. Metabolic scope was calculated at both temperatures for all three fish types. Blood samples were analyzed for blood-oxygen equilibrium fitting curves, P50 and Bohr coefficients.
At 23°C, hybrid catfish had the highest metabolic scope at 559.5 mg O2/kg/hr, followed by channel (431.5 mg O2/kg/hr), and blue (369.1 mg O2/kg/hr) catfish. At 33°C, hybrid catfish had the highest metabolic scope at 764.0 mg O2/kg/hr, followed by channel (622.4 mg O2/kg/hr), and blue (606.8 mg O2/kg/hr) catfish. Additionally, hybrid catfish had the highest critical swimming velocity at both temperatures. Channel catfish had the highest P50 at both temperatures, followed by hybrid and blue catfish. Hybrid catfish had the highest Bohr coefficients at both temperatures, followed by channel and blue catfish. These findings suggest that hybrid catfish are a better performing fish at warm temperatures, in terms of aerobic capacity and blood-oxygen affinity, than channel and blue catfish. These findings provide an improved understanding of the aerobic capacity and blood-oxygen affinity of Ictalurid catfishes.