Effect of Temperature on the Rate of Gastric Digestion in Finger ling Sockeye Salmon, Oncorhynchus nerka

By means of serial slaughter the rate of gastric digestion in yearling sockeye salmon (30–40 g) was studied at approximately 3, 5, 10, 15, 20, and 23 C, after satiation feeding on Abernathy pellets. Subsequently the ash-free dry weight of the stomach contents was determined and expressed as a fraction of the dry weight of the fish. At any one temperature, rate of digestion appeared to be proportional to the mass of food remaining in the stomach (exponential decline). The time for complete digestion decreased from 147 hr at 3 C to 18 hr at 23 C. The time for one-half of a sample of fish to exhibit empty stomachs corresponded closely to that for a mean state of 96% gastric digestion, providing a simple means for determining rate of digestion.