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 advantages of care by two parents and thus biparental care is rare among 'mouthbrooding' fish. We surveyed the breeding biology of Eretmodus cyanostictus, a biparental mouthbrooder from Lake Tanganyika, to understand what factors maintain 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 young while females regain reproductive condition.