Laboratory tests were conducted to determine the effect of salinity on growth and survival of channel catfish, Ictalurus punctatus. Three-day old or older eggs tolerated up to 16 ppt total salinity. However, at the time of hatching there was a sharp drop in tolerance to about 8 ppt. This level of tolerance was maintained during the period of yolk absorption. Following yolk absorption there was an increase in tolerance to about 9 or 10 ppt. By five months of age tolerance had increased to 11 ppt and to 12 ppt by six months. The level of tolerance was about the same at 11-14 months. Nine days acclimation to 5 ppt increased growth and food conversion slightly but did not increase survival. Forty days of acclimation to 5 ppt increased tolerance about 0.5 ppt. Fish failed to maintain themselves at salinities greater than 12 ppt, even with extended acclimation to 10 ppt salinity. In long-term studies, starting at an age of 42 days and continuing through an age of 148 days, fingerlings in freshwater had the best indexes for food consumption, growth, food conversion and survival. Fingerlings in 5 ppt salinity did almost as well. Fingerlings in 10 ppt salinity were a poor third. In long-term studies with 11 through 14 month-old yearlings, when fish were acclimated to 5 ppt, indexes were similar at all test salinities of 0 ppt through 11 ppt. FIsh acclimated to 10 ppt gave similar results at 0 ppt through 12 ppt.
