The experiment described was conducted in water impounded by earth dams, for local water-supply, in Nyanza province, Kenya. Control of snails was attempted by introduction of the malacophagous fish Astatoreochromis alluaudi; other species were also introduced. The schedules of introduction of fish were varied between the reservoirs, and one was left as a control without any introduction of fish. The necessity for the establishment of a fish-rearing pond, prior to large-scale stocking, is emphasized.
Assessment of snail control was made by scooping for snails, catches being expressed per man-hour. This was carried out both before and after introduction of fish, over a total period of 15 years. It is concluded that the data indicate that A. alluaudi did reduce the numbers of some species of snails—particularly Biomphalaria pfeifferi and, to a lesser extent and with less certainty, Bulinus spp.
Two other introduced fish species, Tilapia zillii and T. leucosticta, did not appear to be associated with any fall in snail numbers.