The Marais des Cygnes River has less gradient (especially in the upstream portions), fewer and shorter riffles, and more mud bottom than does the Neosho River. Stream-flow during drought was reduced to a proportionately greater degree in the Neosho River than it was in the Marais des Cygnes River. Average flow of the Neosho River near Parsons (drainage area: 4905 square miles), Kansas, was less than average flow of the Marais des Cygnes River at Trading Post (drainage area: 2880 square miles), Kansas, in 1953, 1955 and 1956. In normal times the Neosho River carries a larger volume of water than the Marais des Cygnes. The Neosho River has a greater variety of habitat-conditions and a more diversified fish-fauna than the Marais des Cygnes. The following species were taken in the Neosho River but not in the Marais des Cygnes River: blue sucker, high-finned carpsucker, golden redhorse, gravel chub, mimic shiner, mountain minnow, parrot minnow, Neosho madtom (the only endemic in either river), mosquitofish, spotted bass, smallmouth, black crappie, logperch and fan-tailed darter. Most of the above species are usually found in association with gravel-bottom, which is prevalent in Neosho River. The blue sucker, high-finned carpsucker, gravel chub, mountain minnow, and parrot minnow normally occur in the larger streams in Kansas. The last three species became more abundant in the Neosho River following resumption of flow. The golden redhorse also increased in abundance from 1957 to 1959, but was most numerous at the upper Neosho station, whereas the other species occurred mainly at the lower stations. The mimic shiner, spotted bass, smallmouth, and fan-tailed darter are characteristic of upstream habitats with clear water (tributaries, rather than the mainstream), and were taken in the Neosho River only in 1957 or became less abundant from 1957 to 1959. The silver chub, slender madtom and tadpole madtom were taken in the Marais des Cygnes River only in 1957 and were not taken in the Neosho River. The following species, common to both rivers, were more abundant in the Neosho: long-nosed gar, short-nosed gar, river carpsucker, creek chub, sucker-mouthed minnow, red-finned shiner, red shiner, ghost shiner, blunt-nosed minnow, fat-headed minnow, stoneroller, yellow bullhead, channel catfish, flathead, stonecat, largemouth, long-eared sunfish, slender-headed darter, and freshwater drum. These species, collectively, reflect the more diversified habitats (more gravel-bottom, more riffle-areas, more gradient, greater range of stream-size sampled) in the Neosho River.