Five genera of gastropod molluscs occur over the sand bottom at Cape Maclear, Lake Malawi
(Lanistes, Bellamya, Melanoides, Gabbiella, Bulinus).
These snails are the primary food for at least six species of the sand-dwelling cichlids.
Knowledge of the population dynamics of these gastropods should contribute to the
understanding and management of fisheries in southern Lake Malawi. The distribution,
densities, and relative abundances of the predominant gastropod genera were determined.
Additionally, the size distributions in relation to depth and cover of vascular
macrophytes were quantified for the most common genus, Melanoides. The results
show that (1) gastropods occurred at all depths sampled; (2) gastropod densities
(to 123/m2) were highest in shallow (1.5-4.5 m) water depths; (3) gastropod
distributions were patchy; (4) density of Melanoides was highest at 3.0 m but
size of Melanoides was highest: at 6.0 m in open sand and at 3.0-4.5 m in
vascular macrophyte microhabitats. Either differential availability of food or
differential predation by fishes among alternative microhabitats, or both, could account
for these patterns.