A field survey of the breeding habits of Eretmodus cyanostictus, a biparental mouthbrooding cichlid in Lake Tanganyika

Oral incubation of young or 'mouthbrooding' reduces the selective advantage s of care by two parents and thus biparental care is rare among 'mouthbrood ing' fish. We surveyed the breeding biology of Eretmodus cyanostictus, a bi parental mouthbrooder from Lake Tanganyika, to understand what factors main tain biparental care. We found larger males than females, a male-biased sex ratio and indications that spawning is synchronized around the full moon. These preliminary findings suggest that the benefits of desertion for males are low; males may maximize their reproductive success by helping raise yo ung while females regain reproductive condition.