EFFECTS OF INTERMITTENT CHLORAMINE-T EXPOSURE ON GROWTH, SERUM BIOCHEMISTRY, AND FIN CONDITION OF JUVENILE RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Chloramine-T is a commonly used therapeutic agent for the treatment of bacterial gill and skin diseases in the intensive aquaculture of salm onids; however, little is known about its effects on healthy fish. Juv enile rainbow trout (Oncorhynchus mykiss) were exposed weekly to 5, 10 , and 20 mg active chloramine-T ingredient.L(-1) in a 20-tank replicat e flow-through facility. Control fish were treated with tank water onl y. Growth parameters and haematocrits were taken twice weekly and seru m biochemistry was measured on termination of the experiment. Absolute growth rates were suppressed but only statistically significantly in fish treated with 20 mg chloramine-T.L(-1) compared with controls. Fis h exposed to 10 and 20 mg chloramine-T.L(-1) showed significant predis position to an erosive dermatitis of the caudal fin which appeared to be caused by opportunistic pathogens of the genus Pseudomonas spp. and Flavobacter spp. Haematocrits decreased in controls and all treatment s. A significant concentration-dependent decrease in plasma sodium and chloride was observed. Plasma glucose levels did not vary and were si milar to those reported for unstressed trout. We recommend that care b e taken when using chloramine-T prophylactically and that concentratio ns of less than 10 mg.L(-1) be used.