Growth performance, hematological and biochemical responses of African catfish (Clarias gariepinus) reared at different stocking densities

African catfish (30.71 +/- 0.89 g) were stocked at four different densities of 35, 65, 95 and 125 kg m(-3) in 120 L aerated tanks for 60 days, with one and a half tanks of water being renewed daily. The effects of stocking density were examined in growth performance and welfare indicators, such as hematological and biochemical indices. Growth decreased with the increasing stocking density, and there is no significant difference between 35 and 65 kg m(-3) treatments. Hematological and biochemical indices, including hemoglobin (Hb), erythrocyte sedimentation rate (ESR), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and the mean corpuscular hemoglobin concentration (MCHC) values, total protein (TP), glucose and total cholesterol (TC) levels, aspartate transaminase (AST), alkaline phosphatase (AP) and lactate dehydrogenase (LDH) activities, serum ion levels and pH, were not affected by the stocking density. Consistent with the result of growth, no significant difference in red blood cell (RBC) count and Hematocrit (Hct) values, alanine transaminase (ALT) activity, albumin (Alb) and triglyceride (TG) levels were observed between 35 and 65 kg m(-3) treatments, while some parameters, such as Hct, Alb and ALT, were affected significantly when stocking density increased to 95 kg m(-3). Impaired welfare indicators, as well as growth performance, need to be taken into account by husbandry practices to assure that high welfare standards are maintained with increasing profitability.