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.