The condition factor and fecundity of the translocated rock-dwelling cichlid fish,
Cynotilapia afra, Pseudotropheus callainos, and Pseudotropheus tropheops
'red cheek' at Thumbi West Island, southern Lake Malawi, were compared with those at
their sites of origin, in the north of the lake. The guiding hypothesis was that these
species, having originated from a region of the lake which is generally poor in nutrients,
and been introduced to an area richer in nutrients, would be in better condition and more
fecund there than at their sites of origin. That seemed to be the case. P. callainos
and P. tropheops 'red cheek' had significantly higher condition factors and fecundity
indices at Thumbi West Island than at their sites of origin. However, both condition factor
and fecundity of all the species studied fluctuated seasonally. The major peaks in condition
factor coincided with either the wind-induced lake upwelling from June to August, or the rains.
Major peaks in fecundity occurred at the end of the rainy season, between February and April,
or at the end of the upwelling period between September and October. The translocated species
began to breed at a smaller size at their sites of origin in the north than at Thumbi West
Island, probably as an adaptive response to a poor nutrient regime in the north. The increase
in population of some translocated species can be partly attributed to their improved condition
and fecundity due to enhanced nutrient availability at the site where they have been introduced.
This may have negative implications for the native taxa, more particularly as competition for
breeding space is rife among the rock-dwelling cichlids of Lake Malawi.