Effects of temperature and salt concentration on latent Edwardsiella ictaluri infections in channel catfish

Juvenile channel catfish Ictalurus punctatus, 10% of which had a natural, latent infection of Edwardsiella ictaluri, were held in water at 15 2C. Following elevation of the water temperature to 25'C for 28 d, 77 % died with clinical E. ictaluri infections. This level of mortality was significantly higher (p < 0.05) than mortality attributable to E. ictalun' when the water temperature was raised to 18C (10%) or to 30C (23 %). Channel catfish naturally infected with E. ictaluri were exposed to 0. 100, 1000, 2000. and 3000 mg 1-' NaCl at 25OC for 28 d. Mortalities of channel catfish held in NaCl concentrations of 0 and 100 mg 1-' (100% and 96% respectively) were significantly higher than those held in NaCl concentrations of 1000, 2000, and 3000 mg 1-' (33, 43, and If %, respectively).