Reintroduction projects may fail because captive-reared animals do not possess the behavioural skills required for survival in the wild. Rearing captive-bred animals in semi-natural enclosures prior to release has been used to improve the survival of reintroduced endangered species, but it is unclear how rearing environment influences the development of behaviour. This study examined the effect of rearing conditions on the behaviour of the goodeid Skiffia multipunctata, an endangered species of Mexican fish. Under standard laboratory conditions, the courtship, aggression, boldness and foraging behaviour of fish raised in aquaria was compared to that of fish reared in outdoor ponds. We present initial behavioural descriptions for this species and show that laboratory-reared fish displayed increased courtship, aggression and curiosity towards a novel predator in comparison to their pond-reared counterparts. Laboratory-reared fish also commenced foraging on a novel food item (Artemia) more rapidly than fish reared outdoors. These findings suggest that captive rearing environments promote the development of behavioural tendencies, such as boldness and aggression, which could be detrimental to the survival of reintroduced individuals. (C) 2004 Elsevier Ltd. All rights reserved.