Q. C. Fontenot and J. J. Isely, South Carolina Cooperative Fish and Wildlife Research Unit, Clemson University, Clemson, SC 29634, and J. R. Tomasso, Jr., Department of Aquaculture, Fisheries and Wildlife, Clemson University, Clemson, SC 29634

Abstract. Ammonia and nitrite concentrations can easily reach toxic levels when fish are kept at high densities. We determined 96 hour LC50 values for ammonia and nitrite for juvenile shortnose sturgeon. The LC50 value for ammonia was preliminarily determined to be 151 mg/l total ammonia-nitrogen. Most of the mortality during the ammonia trials occurred within the first 24 hours. The LC50 value for nitrite was preliminary determined to be 10 mg/l total nitrite-nitrogen. Mortality during the nitrite toxicity trials occurred throughout the 96 hour period, which suggests a slow rate of nitrite uptake for shortnose sturgeon.