Effects of Stocking Density on Growth, Nonspecific Immune Response, and Antioxidant Status in African Catfish (Clarias gariepinus)

African catfish were stocked at densities of 35, 65, 95, and 125 kg/m(3) for 60 days. The effects of the stocking density on growth, non-specific immune response, and antioxidant status were investigated on days 30 and 60. Serum cortisol levels were assayed on day 60. Increased stocking density led to decreased growth. Most non-specific immune indices (total number of leukocytes, differential leukocyte count in percent, respiratory burst activity, C3 and C4 complements, spleen and head kidney mass indices) were unaffected by the stocking density (p>0.05). There were significant differences between the 35 and 125 kg/m(3) treatments in lysozyme activity on day 60 (p<0.05) but no significant effects of stocking density on malondialdehyde (MDA) level on either day 30 or day 60 (p>0.05). On day 30, only glutathione peroxidase (GSH-Px) activity was stimulated by increased stocking density while, on day 60, increased stocking density resulted in increased glutathione (GSH), GSH-Px activity, and superoxide dismutase (SOD) activity. The serum cortisol level on day 60 was unaffected by stocking density (p>0.05). Findings suggest that high physiological welfare standards were maintained in African catfish reared in high stocking densities.