Observations that I made in a pond owned by Dr. E. C. Bryan of Erie indicated that channel catfish, when disturbed in the early stages of guarding the eggs, either eat the eggs and abandon the nest or leave the nest exposed to predation by other animals. In the later stages of nesting, the fish, if removed, will return to guard the nest. After the eggs hatch the guarding response probably diminishes and the fish leaves the nest readily.

At the lower Neosho station, several "artificial" holes were dug into the clay bank and two pieces of six-inch pipe were forced into the bank. Nearly all these holes were occupied by catfish for a short period in June; many of the holes were enlarged, either by the current or by fish. I suspect that fish enlarged some holes, because in the spawning season several males were observed that had large abrasions atop their heads, around their lips, and to a lesser extent on their sides. These could have been caused by butting and scraping the sides, roof and floor of a hole. I found it possible to enlarge the holes by rapidly moving my hand while it was inside a hole.

The growth-rate of channel catfish in the Neosho was approximately the same at all stations, and the large 1957 year-class grew to an average size of about nine inches by mid-September, 1959 (Table 7). Channel catfish mature at a total length of 12 to 15 inches. Thus, most individuals of the 1957 year-class in the Neosho River probably will mature in their fourth or fifth summer (1960 or 1961 spawning season).

The sizes attained by young-of-the-year in 1957 differed in the two rivers. Six hundred and thirty-three young taken in the Marais des Cygnes River attained an average size of 4.7 inches (range two to six inches) by mid-September. (Age was determined by length-frequency and verified by examining cross-sections of fin-spines from the larger individuals). One hundred and fifty young from the Neosho River averaged 3.0 inches (range 2 to 3.7 inches) on 2 November. Gross examination of the riffle-insect faunas indicated a larger standing crop in the Neosho than in the Marais des Cygnes River. Thus, the slower growth of young channel catfish in the Neosho seemed not to be correlated with food supply. Bailey and Harrison (1948:125-130) found that young channel catfish in the Des Moines River, Iowa, fed almost exclusively on aquatic insect larvae. My observations indicate that this is true in the Neosho and Marais des Cygnes rivers also.

Young produced in 1958 in the Neosho River attained an average total length of three inches by 26 August, and young produced in 1959 attained an average size of 3.5 inches by 11 September. Both groups probably continued growth until October, and may have averaged four inches total length at that time.

The 1958 and 1959 year-classes were much less abundant than were the 1957 young. Therefore, it seems likely that the growth of the 1957 young in the Neosho River was depressed because of crowding. The 1959 year-class was larger than the small 1958 year-class, thus conforming to a general expectation that strong year-classes will be followed by weak year-classes.

Reproduction by channel catfish in 1957 seemed greater in the Neosho River than in the Marais des Cygnes River (Table 10); this coincided with a greater change in volume of flow in the Neosho River than in the Marais des Cygnes River (Tables 1-4). The 1957 year-class seemed more crowded, and grew more slowly, in the Neosho than in the Marais des Cygnes River.

Ictalurus natalis (LeSueur)
Yellow Bullhead

Yellow bullhead were taken only at the middle station on the Marais des Cygnes and upper station on the Neosho. The yellow bullhead is more restricted to streams than is the black bullhead. Both species decreased in abundance during a period of continuous flow (1957 to 1959) following drought at the upper Neosho station. Collections in 1958-'59 indicated an increase in average size. Of four individuals marked and released at the upper Neosho station in 1959, one was recaptured about three hours after being released. It had not moved from the area of release.

Ictalurus melas (Rafinesque)
Black Bullhead