Effects of strain and body weight on low-oxygen tolerance of channel catfish (Ictalurus punctatus)

Low-oxygen tolerance is important for aquaculture species, because exposure to hypoxia can result in heavy mortalities. This study evaluated the effects of strain, body weight, and gender on low-oxygen tolerance in channel catfish (Ictalurus punctatus) exposed to a lethal concentration of dissolved oxygen (0.1 mg/L). The variation in low-oxygen tolerance, assessed as the time to loss of equilibrium, of channel catfish from six strains (103KS, Kansas, KMix, Marion, Marion S, and Thompson) was examined. Catfish (15-179 g) showed a large variation in resistant time to hypoxia, ranging from 8 to 104 min, and both strain and body weight contributed significantly to this variation (P < 0.05). 103KS and Marion S strains had higher low-oxygen tolerance than the other strains, while the Marion strain had the poorest low-oxygen tolerance (P < 0.05). In addition to genetic background, body weight positively correlated with low-oxygen tolerance, but there were no significant differences between female and male catfish in low-oxygen tolerance. The results indicate that genetic background and body weight are important factors that contribute variations in low-oxygen tolerance.