In 1959, 96 black bullhead were taken at the upper Neosho station (five in Area 1 and 91 at the White Farm). In these collections, 25 were marked (fin-clipped or dyed) and six were recaptured. Four of the six had not left the area of capture one and two days after being released. The fifth fish recaptured was one of five individuals that had been displaced one pool downstream. When recaptured seven days later, this fish had moved upstream over two steep riffles (two to three inches deep, 75 feet and 166 feet long) past the site of original capture to the next pool. The sixth fish, marked at the same time but returned to the original pool, was recaptured nine days after original capture and had moved upstream over a long riffle (two to three inches deep, 166 feet long) and a short riffle into the second pool above the original site of its capture. Rotenone was applied to a small (.04 acre-feet) backwater ditch having a soft mud bottom at the upper Marais des Cygnes station on 25 July, 1957; 1526 black bullhead, one green sunfish and one white crappie were collected. A sample of 60 bullhead averaged 4.6 inches T.L. (range 3.5 to 6.6 inches) and 540 individuals averaged .7 ounce each. These fish probably represented the 1956 year-class. The upper Neosho station had a large population of black bullhead, strongly dominated by fish less than four inches T. L. (range 1.5 to 3.8 inches), in the spring of 1957. Most were approximately two inches T. L. and probably represented the 1956 year-class. Growth, according to length-frequency, following restoration of stream-flow, shows a regular increase in length of this dominant 1956 year-class (Fig. 3). A scarcity of young, especially in 1958 and 1959, is apparent in Fig. 3. This may be due to the fact that a strong year-class usually is followed by one or several weak year-classes. However, it more probably reflects the fact that black bullhead are characteristically pond fish, and as such are not so well adapted to reproduction in flowing streams as are many other species. Metcalf (1959) found this species most abundantly in the intermittent headwaters of Walnut River and Grouse Creek in Cowley County, Kansas. [Illustration: FIG. 3. Length-frequency of black bullhead at the upper Neosho station, 1957, 1958 and 1959.] #Pylodictis olivaris# (Rafinesque) Flat-headed Catfish The flathead is the largest sport-fish occurring in Kansas. Several weighing more than 40 pounds are caught from streams each year, and the species reportedly attains sizes in excess of one hundred pounds. Several aspects of the biology of the flathead in Kansas have been discussed by Minckley and Deacon (1959).