The impact of intralacustrine introductions with regard to space utilization and competition for territories to a cichlid fish community in Lake Malawi,Africa

At Thumbi Island West in Lake Malawi, a number of cichlid species was introduced from elsewhere in the lake some 20 years ago. These are now, in part, well established and could have an effect on the indigenous fish fauna. Repeated removals of the males of the introduced species from their territories were undertaken and artificial miniature reefs were established to find out whether the emptied existing territories or the newly established potential territories would be occupied by indigenous species. The results show that the emptied territories were almost invariably re-occupied by either a male of the introduced species conspecific to the previous territory holder or they remained empty. The newly established miniature reefs were not occupied by territorial males of either introduced or indigenous species but by young fish of a variety of species.