EFFECTS OF CHANGES IN FISH POPULATIONS IN LAKE VICTORIA ON THE FOOD OF OTTERS (LUTRA-MACULICOLLIS SCHINZ AND AONYX-CAPENSIS LICHTENSTEIN)

Observations were made on feeding by spotted-necked otters (Lutra maculicollis), and the Cape clawless otter (Aonyx capensis), in Lake Victoria, Tanzania. Spotted-necked otters lived mostly in small packs. Their prey consisted mainly of cichlid fishes. A method is described for estimating prey size from the diameter of fish eye-lenses found in the otters' faeces. Spotted-necked otters took mostly small prey but they also often ate relatively large, introduced fish species, in contrast to reports on their food elsewhere and in Lake Victoria before the recent change in fish populations. Clawless otters ate mostly crabs. The populations of spotted-necked otters have declined along most coasts of Lake Victoria, possibly because of changes in fish populations and vegetation. Introduced fish species were preyed upon in certain types of shore-line vegetation especially on uninhabited islands. The clawless otter is not likely to be affected by the changes in fish populations.