Temporal patterns in diet and rate of food consumption of the three‐spined stickleback (Gasterosteus aculeatus L.) in Llyn Frongoch, an upland Welsh lake

Abstract

SUMMARY. 1. Monthly and diel patterns of food consumption by the three‐spined stickleback, Gasterosteus aculeatus L., were studied in Llyn Frongoch, a small reservoir in upland mid‐Wales.2. Copepods were particularly prominent in the diet in spring and autumn, with ephemeropteran nymphs prominent in summer. Chironomid pupae and stickleback eggs were also elements of the diet in summer, whereas algae, plant material and debris were more important in autumn and winter. Chironomid larvae and ostracods were present throughout the year, but there was some doubt as to the importance of ostracods as digestible food items.3. Stomach contents were heaviest in spring and late summer and lightest in late autumn and winter.4. Samples for the diel samples were taken four times, once in each season. These diel samples largely reflected the seasonal changes in diet noted in the monthly samples. There were few cases of a clear switch in the composition of the diet during a 24 h period. Feeding occurred during daylight, the weight of the stomach contents declined during darkness.3. Several methods provided estimates of the daily rate of food consumption which ranged from 3.5 mg in December (4°C), to 19.0 mg in May (15°C). These estimates and others obtained independently suggest that the annual rate of food consumption for a stickleback in Llyn Frongoch is between 2000 and 5000 mg wet weight.