EFFECTS OF TEMPERATURE AND SALT CONCENTRATION ON LATENT EDWARDSIELLA-ICTALURI INFECTIONS IN CHANNEL CATFISH

Juvenile channel catfish Ictalurus punctatus, 10% of which had a natur al, latent infection of Edwardsiella ictaluri, were held in water at 1 5 +/- 2 degrees C. Following elevation of the water temperature to 25 degrees C for 28 d, 77% died with clinical E. ictaluri infections. Thi s level of mortality was significantly higher (p < 0.05) than mortalit y attributable to E. ictaluri when the water temperature was raised to 18 degrees C (10%) or to 30 degrees C (23%). Channel catfish naturall y infected with E. ictaluri were exposed to 0, 100, 1000, 2000, and 30 00 mg l(-1) NaCl at 25 degrees C for 28 d. Mortalities of channel catf ish held in NaCl concentrations of 0 and 100 mg l(-1) (100% and 96% re spectively) were significantly higher than those held in NaCl concentr ations of 1000, 2000, and 3000 mg l(-1) (33, 43, and 17%, respectively ).