Technical Abstract: Effects of high summer temperatures on channel catfish (Ictalurus punctatus) are poorly understood, particularly for thermal regimes that mimic pond aquaculture conditions. Therefore, this study examined the effects of three cycling upper-range temperature regimes (23-27ºC, 27-31ºC, and 31-35ºC) characteristic of culture environments in the Mississippi Delta. Feed conversion ratio, feed consumption, specific growth rate, activity levels, survival, and overall growth in terms of wet weight and total length (TL) were measured in fingerling channel catfish over an eight week period in a flow-through, multiple-tank system. Specific growth rate, feed consumption, TL, and wet weight increased significantly in the 27-31ºC treatment in contrast to the 23-27ºC and 31-35ºC treatments. Feed conversion ratio was lowest in the 27-31ºC treatment whereas activity levels were highest in the 31-35ºC treatment. Survival significantly decreased for catfish in the warmest treatment compared to catfish in the coolest treatment. These results indicate that high temperatures decrease growth in channel catfish, largely due to reduced food consumption and feed conversion, and increased levels of activity. Therefore, increases in temperatures, such as from climate change, present challenges to the culture and management of channel catfish.