Food Habits of the Flathead Catfish, Pylodictis olivaris (Rafinesque), in Relation to Length and Season in a Large Kansas Reservoir

Abstract

Frequency of occurrence, numbers, and volumes of organisms in stomachs of various age and size groups of 172 flathead catfish (Pylodictis olivaris) from Milford Reservoir in northcentral Kansas were determined for each month from April through November 1975. Flathead catfish between 201 and 500 mm consumed mostly benthic macroinvertebrates and fishes, while those over 500 mm almost exclusively are gizzard shad (Dorosoma cepedianum). Diets of piscivorous flathead catfish appeared to shift seasonally. Two-year-old flathead catfish relied heavily on large benthic macroinvertebrates such as crayfish (Orconectes sp.) but this dependence decreased gradually until age six, when the flathead catfish were almost entirely piscivorous. Changes in food habits may be related to physical size of the predator and physical exclusion from habitat occupied by crayfish. The flathead catfish did not prey actively on rough fish populations, probably because gizzard shad of small size were readily available. The relatively fast growth of flathead catfish in Milford Reservoir suggests that an abundance of forage fishes limited competition for food. The flathead catfish (Pylodictis olivaris) is commonly found in rivers of eastern Kansas and specimens weighing more than 18.1 kg (40 pounds) are taken from rivers in the state each year. Because of its fighting ability, edibility, and potential for reaching a large size, the flathead catfish is held in high regard by fishermen (McCoy, 1953). A creel census showed 1755 flathead catfish averaging 4.41 kg each, and totalling 7494 kg were harvested in 1974 from Milford Reservoir, Kansas (Groen, personal communication). Brown and Dendy (1961) found that flathead catfish from Alabama rivers were mainly piscivorous. Other authors suggest that the actual abundance I The author's present address is Oklahoma Cooperative Fisheries Research Unit, Life Sciences West 433, Oklahoma State University, Stillwater, Oklahoma 74074. This content downloaded from 157.55.39.112 on Wed, 07 Sep 2016 04:41:56 UTC All use subject to http://about.jstor.org/terms VOLUME 83, NUMBER 4 201