Abstract

Channel catfish were maintained under conditions of low (15.4°C) and fluctuating (15.4 to 26.9 °C/24 hours) temperatures, low (126 mg/L NO₃-N) and high (289 mg/L NO₃-N) nitrate in recirculating systems, crowding (171 g body mass/L), and fasting. They were vaccinated with formalin-killed enteric red mouth bacterium, and antibody titers were monitored weekly for 10 weeks. Only those fish maintained in low or fluctuating temperature environments has significant (P< 0.01) immunosuppression. The other environmental conditions studied, which are commonly encountered in intensive fish culture operations, did not compromise the humoral immune response of channel catfish.

Notes

Stress Parameters

Temperature, crowding, starvation, low oxygen, pH, NH₄, NH₃, NO₂, NO₃, handling.

Reaction to Stress

ACTH is released from the hypothalamus. It then travels to the intrarenal tissue (rather than adrenal) of the fish. The result is release of cortisol and epinephrine, with decreased lymphocyte and antibody production.

Results

Low temperatures dramatically depressed the immune response but starvation, crowding and high nitrite levels did not affect the immune response. Pheromones can lower the immune response.