Condition and fecundity of translocated rock‐dwelling cichlid fish in Lake Malawi

Abstract

The condition factor and fecundity of the translocated rock-dwelling cichlid ®sh, 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 signi®cantly 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¯uctuated 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.

Reproduction and fecundity of tucunaré,Cichla kelberi(Perciformes: Cichlidae), an exotic species in Três Marias Reservoir, Southeastern Brazil

“…Variations in fecundity values can occur among species of the same genus or among fishes of the same species, related to distinct environments, size and age of fish, consecutive reproductive periods, differences in the ability of food assimilation and local environment conditions (Bagenal and Braum, 1978;Coward and Bromage, 1999;Fawole and Arawomo, 2000;Brown-Peterson et al, 2002;Campos-Mendoza et al, 2004;Osure and Phelps, 2006;Duponchelle et al, 2007). In fact, environmental conditions have an important influence over reproductive characteristics, as was noted in three species of Cichlidae: Cynotilapia afra, Pseudotropheus callainos and Pseudotropheus tropheops, where their fecundity increased in the introduced habit, probably due to enhanced availability of food as compared to their natural habitat (Munthali and Ribbink, 1998).…”

“…Furthermore, fecundity data provide important information for fish management and species conservation (Sato et al, 2003). In reservoirs, introduced species may have an increased fecundity in those cases where they find more suitable conditions for their survival (Munthali and Ribbink, 1998).…”

Reproductive isolation among closely related Lake Malawi cichlids: can males recognize conspecific females by visual cues?

“…The condition of the females used in the experiment was as variable as that of natural populations. Munthali & Ribbink (1998) calculated a condition factor for P. callainos individuals at Nkhata Bay of 0.92 0.11 (X SD). The condition factor of the females used here, following Munthali & Ribbink's calculations, was 1.00 0.09 (N=192; the condition factor and variance were the same whether the P. callainos 'blotched' morph was kept in the analysis (N=192) or not (N=168)).…”

Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids

“…Furthermore, Streelman et al . (2004) found support for recent hybridization between an introduced population of Cynotilapia afra (Munthali & Ribbink 1998) and the native species M. zebra in Lake Malawi National Park. Hybridization occurs in the wild between morphologically diagnosable cichlid lineages endemic to Lake Malawi.…”