The effects of juvenile social interaction on growth rate, size and age at maturity, and adult social behavior in Girardinus metallicus Poey (Pisces: Poeciliidae).

The aim of the following experiments is to identify and to describe those factors most probably important in determining reproductive success in male Girardinus metallicus and to investigate how competition among juveniles affects these characters. The quantitative relationships among male size, male aggressiveness, and male sexual activity are examined. Small male are either more aggressive or less affected by aggression than large male, and they tend to exhibit higher sexual vigor. Male which are subordinate to other individuals as juveniles mature later at a larger size and tend to be less sexually active than male dominant as juveniles. Juvenile male are more aggressive than juvenile females. The results are discussed in terms of the ecology of the species, and interspecific comparisons are made.