Biology of the Flathead Catfish in Kansas

Flathead catfish (Pylodictis olivaris) were collected from the Big Blue River, a highly turbid stream, and the Neosho River, a relatively clear stream, in Kansas, mostly by A. C. electric fishing gear. Flathead catfish comprised 15.1 percent of the number of fish taken from the Big Blue, and 10.5 percent of those from the Neosho. Individuals less than 4.0 inches long (total length) were found in riffles; those 4.0 to 12.0 inches long were generally dispersed in the stream; those 12.0 to 16.0 inches long were associated with cover (logs, brush-piles and rocks) in intermediate depths; and those longer than 16.0 inches were solitary, near large cover (especially logs and down trees) in deeper pools. Examination of 258 stomachs, 69 of which were empty, showed that food of flathead catfish 4.0 inches and shorter was nearly all insect larvae; that of fish 4.1 to 10.0 inches, insect larvae, fishes, and crayfish; and that of larger flathead catfish mostly fish and crayfish. Kinds of food eaten evidently depended on its availability. Young-of-the-year fish were 2.8 inches long in August in the Big Blue River, and 2.7 inches in the Neosho. Later growth in the Big Blue was faster than in the Neosho and five-year-old fish from these two streams had average total lengths of 24.8 and 17.0 inches, respectively. Length-weight relationship is presented. Male catfish in these streams become sexually mature at 15 to 18 inches long (3 to 5 years) and females matured at 18 to 20 inches (4 to 6 years). Sex ratio was approximately 1:1. Spawning occurred from late June to late July, and 6,900 to 11,300 eggs were found in females 21.0 to 24.0 inches long. The cestode, Marsipometra, was a common parasite in the duodenum and nematodes occurred occasionally in the hindgut.