Functional implications of early sexual growth dimorphism in vundu

Female juvenile vundu Heterobranchus longifilis outweighed males by >60% (P<0.0001) margins when aged 142 or 177 days. Not only did females grow faster (P=0.0494) than males during the experiment, but they also outweighed them by a 38.5% margin at the start of the experiment (86 days: P=0.0109). Sexual growth dimorphism (SGD) was estimated as having arisen at 15 +/- 10 days. Vundu aquaculture could be improved substantially by monosex female rearing. Because the modelled emergence of SGD corresponded precisely with the start of type II cannibalism, it was suggested that cannibalism among juvenile vundu be exerted essentially by females, and might have different impacts on faster-growing females and slower-growing males. (C) 1999 The Fisheries Society of the British Isles.