A study of the swimming capabilities of blue, Ictalurus furcatus, and channel, I. punctatus, catfish

The comparative aerobic and anaerobic swimming capabilities of blue, Ictalurus furcatus, and channel, I. punctatus, catfish fingerlings were examined. The study was conducted to gain insight into the swimming and physiological capabilities of these sympatric species and relate these abilities to their habitat usage. A modified swimming tunnel respirometer was constructed for use in these swimming and physiological studies. Non-horizontal locomotion was examined using a critical swimming speed (Ucrit) protocol, and blue catfish Ucrit was lower than channel catfish Ucrit when swimming at 0° (horizontal), all inclined angles tested (+15°, +30°, +45°, and +60°), and declined angles of −15°. For inclining angles, Ucrit decreased linearly as angle of incline increased, but for declining angles, Ucrit was non-linear, decreasing to a minimum at −30°. Using a time to fatigue protocol, blue catfish were found to fatigue more rapidly than channel catfish at all speeds from 50–120 cm/s. Channel catfish were shown to have a narrower body from the posterior edge of the operculum to the posterior edge of the dorsal fin, a longer upper caudal fin lobe, and a narrower caudal peduncle than blue catfish fingerlings. Collectively, these factors have been shown to be representative of a more fusiform body shape, which has been linked to superior sustained and prolonged swimming abilities. Though differences in swimming abilities of these two species were demonstrated, no differences in recovery from exhaustive exercise were determined. Channel and blue catfish fingerlings showed no differences in the pre- or post-exercise concentrations of plasma lactate, glucose, cortisol, or muscle lactate. Blue and channel catfish are found in a wide variety of habitats, and studies have reported that channel catfish have the ability to occupy all available habitats within a lake environment when blue catfish are not present. Since channel catfish have been demonstrated in this study to be better swimmers, and no differences in the ability to recover from exhaustive exercise were determined, it is likely that some mechanism other than swimming ability is the cause for blue and channel catfish habitat segregation in their natural habitats.