Environmentally related life history variations in Geophagus brasiliensis

The hypothesis of environmentally related life history variations between two Geophagus brasiliensis populations was investigated by comparing riverine and lacustrine populations. Mean standard length and length at maturity were higher in the lagoon population. Higher fecundity and gonado-somatic indices reflected higher reproductive investment in the river population. In the river, reproduction took place throughout the year, whereas in the lagoon spawning was restricted to spring and summer. Both populations presented synchronous oocyte development, indicating total spawning. Nevertheless, the variation in traits suggests that both populations exhibit environmentally related variations in their life history patternss.