Loss of shoaling preference for familiar individuals in captive-reared crimson spotted rainbowfish Melanotaenia duboulayi.

Captive-reared rainbowfish Melanotonia duboulayi showed no preference for familiar individuals in an experiment examining shoaling preferences. Fortnightly re-examination of the shoaling preferences of the captive-reared population showed that the lack of preference for familiar individuals did not alter over an 8 week period. The same experiment performed on laboratory-reared offspring raised in isolated groups for 8 months since hatching also showed no preference for shoals consisting of familiar individuals. In contrast, trials performed on a wild population of M. duboulayi found a strong preference for familiar shoalmates, a result that is consistent with previous studies. The lack of shoaling preferences in captive-reared populations is probably the result of relaxed selection and inbreeding in the captive environment. The consequences of captive breeding for fish social behaviour are discussed with particular reference to hatchery production.