Abstract
We studied here the effect of predation risk on size and shape during the development of the Cyprinid fish (Barbonymus gonionotus). In the experiment, juvenile silver barbs (Barbonymus gonionotus) were developing either together or not together with the predator snakehead fish (Channa striata) during 25 days. Predation was limited by isolating the predator from the silver barb with a net. In replicated trays, 60 fish were randomly selected and compared before and after the experiment in presence and absence of the predator. The experiment was replicated three times. Fourteen landmarks were recorded on the fish body and a generalized Procrustes superimposition was performed. Analyses of variance and linear discriminant analyses were used to detect effects of the predator presence on body shape and growth pattern. Results show that if presents, effect of the predator on size and shape evolution in silver barbs is very subtle. A small increase of size and a decrease in relative caudal peduncle height could be reported in all cases suggesting either that the predator could exert directional selection or that developmental plasticity induced by the predator was present. In the case of shape, this developmental plasticity appears to be maladaptive in the experiment because the predator may have selected for these shape attributes in the tank showing the highest predation rate. Finally we found that shape variation decreased with development suggesting that phenotypic canalisation was acquired during the ontogeny of the fish but that size differences among individuals were accumulating with ontogeny.