Daily ration of adult perch, Perca fluviatilis L. during summer in Loch Leven, Scotland

Adult perch, Perca fluviatilis L., were sampled at 3-hourly intervals throughout 24-h periods from June-September 1971, and in June and August 1972. The wet weight of each major food component from the stomachs was expressed in parts per 10 000 of the fresh weight of the fish. From samples at capture, and others taken from caged fish at known time-intervals after capture, the rate of stomach evacuation was estimated. Food consumption between netting times was calculated as the increment between successive initial values of stomach contents, plus the amount evacuated in the interval. As the evacuation rate of caged fish was slower than that of free fish the estimates of food turnover are minimal ones. The perch were consuming 6.5 % of their wet body weight per day in June, and this ration had decreased to 3.2% by September.