Effect of differential gastric evacuation and multispecies prey items on estimates of daily energy intake in juvenile Chinook salmon

The caloric density of stomach contents in juvenile chinook salmon,Oncorhynchus tshawytscha, was not affected by gastric evacuation, suggesting a constant caloric density of stomach contents during evacuation. Differences in the caloric density of prey consumed did affect caloric density of stomach contents over a 24-h period. Consumption of the amphipodCorophium sp. was associated with reduced caloric densities of stomach contents. During periods whenCorophium contributed more than 4% of the stomach contents, average caloric density declined from 5.56 to 5.33 kcal g⁻¹. Despite this difference, estimates of daily energy intake of juvenile chinook salmon were only 3%, greater when developed from the mean caloric density of stomach contents excludingCorophium.