Asymmetric Interspecific Territorial Competion Over Food Resources Amongst Lake Malawi Cichlid Fishes

Abstract

Over the last few million years, Lake Malawi cichlids have evolved into the most diverse community of endemic fishes in the world. The rocky littoral zones of this lake contain (a) densities of up to 22 species of cichlid and (b) more than 500 individuals in a 50m2 area. Most of these cichlids feed on algal mats composed of attached algae and microbes.

This document states that the rock-dwelling cichlids in Lake Malawi comprise the most diverse freshwater fish community in the world. Individuals frequently interact with heterospecifics through feeding territoriality. Underwater observations and experiments were conducted to examine interspecific variation in the frequencies of territorial behaviour and its influence on the feeding habits of heterospecifics.

Frequencies of chasing and fleeing associated with interspecific territoriality were remarkably different amongst 10 cichlid species. In addition, individual fish that attacked heterospecifics more frequently were attacked less often by them, suggesting that interspecific interactions amongst cichlid species are asymmetric.

The experimental removal of territory owners belonging to the most aggressive species resulted in almost fivefold increase in feeding within territories, suggesting that territorial aggression preserves food resources for the territory holder and influences the feeding habits of other species, including those with some dietary dissimilarities. Additional information regarding asymmetric interspecific interactions would improve understanding about how diverse cichlids within trophic groups manage to coexist.