Effect of Stress on Ontogeny of Humoral Immunity in Catla

The present study aimed to evaluate the crowding and handling stress with increased cortisol production, its effect on growth and ontogeny of humoral immunity in Catla catla. Fishes were stressed at different stocking densities (T1, T2, T3 and T4) in crowding stress and were monitored for various parameters including length, weight, serum cortisol and immunoglobulin. In comparison to low stocking density group T1 (3000/ m), high stocking groups (T2, T3 and T4) showed reduction in both average length and weight on 6th day onwards up to 40th day. The results of T4 (18000/m) showed drastic reduction up to 12th day and died afterwards. Similarly, in handling stress fishes were stocked in six hapas at equal densities (3000/m) with different stress (HS1, HS2, HS3, HS4, HS5 and HS6) revealed a decrease in average length and weight in comparison to control throughout the study period. Serum cortisol levels were significantly elevated (P<0.05) in higher crowding and handing stress groups. The results of ELISA for crowding stress showed that immunoglobulins were detectable in the spawn from 3 days post hatching (DPH). The immunoglobulin levels decreased till 18 DPH in T2, T3 and T4 groups, although the levels were significantly higher (P<0.05) in lower stocking density group (T1). In response to handling, all the stressed groups showed significant decrease (P<0.05) in immunoglobulin production in comparison to control at 18 DPH onwards. A slow recovery was observed on 40th day, although the immunoglobulin levels in stressed groups were remained lesser than the control.