title: Individual growth trajectories of sibling Brycon moorei raised in isolation since egg stage, and their relationship with aggressive behaviour.
abstract: The growth of sibling dorada Brycon moorei (Characidae) housed individually in small enclosures (0·25 l; 27·0° C, range ±0·5° C; 12L:12D) from the egg stage was examined at regular intervals until 36 days after hatching (dah) and compared with their behaviour. From 1 to 8 dah, when cannibalism is intense among B. moorei raised in groups, there was no significant increase of size heterogeneity among isolated fish (c.v. of total length of 3·1 and 3·6%, at 1 and 8 dah, respectively) and no primacy of early size differences either. These results suggest that cannibals of B. moorei raised in groups are not natural-born killers with greater growth capacities than others. Size heterogeneity among isolated fish increased significantly first when B. moorei were weaned on formulated feed (8-15 dah), then again from 24 to 36 dah when the average growth rate was half as fast as before (c. 0·5 v. 1·0 mm day(-1) ), despite fish consistently feeding. During both periods, there was a significant, positive relationship between individual growth and aggression or boldness. These results suggest that (1) boldness can favour the transition to a new food type and (2) fish exhibited a variable responsiveness to spatial restriction in small enclosures, which may have been alleviated in some individuals by establishment of territorial behaviour, as suggested by their enhanced aggression.
authors.affiliation: IRD, UR 175, BP 5095, Rue J.F. Breton 361, BP 5095, F-34196 Montpellier Cedex 05, France. Etienne.Baras@ird.fr
authors.forename: E
authors.initials: E
authors.lastname: Baras
authors.forename: M C
authors.initials: MC
authors.lastname: Lucas
mesh_terms: D000374:Aggression; D000818:Animals; D001522:Behavior, Animal; D049628:Body Size; D002190:Cannibalism; D005399:Fishes / Q000254:growth & development* / Q000502:physiology; D016014:Linear Models; D013731:Territoriality