In fish whose body temperature varies with water temperature, digestion and metabolism also are very much affected by water temperature. Fish feed less consistently during cool weather, and nutrient requirements, the ability to assimilate some types of food, and the deposition of body fat and protein in warm water fish all are affected by change in water temperature. Although there has been relatively little research directly related to cool weather feeding of farm-raised channel catfish, the following nutrition-water temperature interrelationships have been demonstrated with warm water fish: 1) Food moves through the gut more slowly at low temperatures; 2) Catfish will feed when hungry, or the gut is empty, even at very low water temperatures. However, at low temperatures, the gut empties more slowly and the fish may not become hungry as quickly as at higher temperatures; 3) Percentage digestibility and/or metabolism of starch and vegetable proteins is poorer at lower water temperatures; 4) Fish respond to higher percentages of protein at higher water temperatures; 5) Water temperature affects deposition of fat and protein in the body of intensively-fed channel catfish. A winter-feeding experiment to measure changes in weight and body composition (fat and protein) of channel catfish concluded that winter feeding was much more profitable than not feeding and that the fed fish contained more protein and less fat than the non-fed fish. The fed fish also had higher percentages of protein than fall-harvested catfish.