Food items were found in 47.0% of 1329 flathead catfish stomachs collected by gill and trammel nets from six Oklahoma reservoirs: Carl Blackwell, Eufaula, Fort Gibson, Grand, Hudson, and Texoma. The average number of food items was 1.6 per stomach and the average volume per stomach was 26.4 ml in stomachs with food. Fish comprised more than 95% of total food volume and total number of food items in all six reservoirs. Gizzard shad contributed from 49.5 to 91.7% of total stomach volumes. Freshwater drum were second in importance as forage, accounting for 3.3 to 38.2% of total volumes. Carp contributed 23.2 and 42.0% of total stomach volumes on lakes Eufaula and Hudson, respectively, but were not found elsewhere. Channel catfish comprised 13.8% of the stomach volume in flatheads from Fort Gibson Reservoir where they were very abundant. All species of centrarchids comprised only 5.4 to 10.0% of total stomach volumes in three reservoirs. The average standard length of 467 measurable forage fish was 127 mm. The average lengths of gizzard shad (age 1+), freshwater drum, and channel catfish were similar, ranging from 134 to 147 mm (S. L.). Of 718 identifiable fish, only two white crappie and one channel catfish were of harvestable size. Flathead catfish feeding activity was greatest in September through October and April through May. Feeding activity was less during the winter months and in June and July when spawning occurred. Feeding activity increased in August following spawning. Gizzard shad decreased in importance as forage during spring and summer months in most reservoirs. Centrarchids and channel catfish were more important during late spring and summer. Flathead catfish predation in reservoirs is probably determined by the availability of suitable-sized forage species near the reservoir bottom in water depths inhabited by flathead catfish. The desirability of flathead catfish as a predator in Oklahoma reservoirs is related to their predation on large forage fishes which are non-vulnerable to the average size piscivorous game fish.
