The total number of adult fish in Lake Frances Case, a main steam Missouri River Reservoir, has declined since impoundment in 1952. Goldeye, channel catfish, and northern redhorse have probably remained the same; emerald shiner, white bass, walleye, and possibly flathead catfish have increased. The sauger population began to decline at about the time walleye numbers increased. Some species formerly present have become rare. Forage species in the reservoir were gizzard shad, emerald shiner, and yellow perch, but these were not present in large enough numbers to provide an abundant forage fish population.

Water management of the Lewis and Clark Lake for flood control, hydroelectric power, navigation, and other purposes affected fish population levels. Fluctuating water levels in May and June affected fish spawning and survival of young. Suggested management measures may improve sport fish abundance, such as construction of spawning and nursery ponds near the reservoir or maintenance of higher water levels during May and June to enhance the reproduction opportunities for desirable species are either too costly or inconsistent with the primary flood-control function of the reservoir. Fish abundance with the present water management regimen will probably remain similar to that of the early 1970's.