Rinse fish thoroughly in cold water; pat dry. Coat fish heavily with salt inside and out. Cover and chill overnight.
Rinse salt off fish; pat dry.
Prepare charcoal fire in smoker, and let burn 10 to 15 minutes. Add hickory chips. Place water pan in smoker, and fill with hot water.
Place fish on food rack. Cover smoker with lid; cook 4 hours according to manufacturer's instructions or until fish flakes easily when tested with a fork.
Leave fish in smoker until fire dies down and fish is cool. Transfer fish to a serving platter.
Note: Smoked catfish may be refrigerated up to 2 weeks.