The effects of visual social stimulation upon age at first spawning in the mouth-brooding cichlid fish Sarotherodon (Tilapia) mossambicus (Peters)

The effect of visual social stimulation upon age at first spawning of Sarotherodon (Tilapia) mossambicus was studied by rearing newly-released young in one of two conditions: isolated or in visual contact with a conspecific of the same age in an adjacent aquarium. Results indicated that isolation delayed first spawning by about 10 days for isolated females as compared to socially stimulated females. The rate of colour development was the same for all males suggesting that testicular maturation was not greatly affected by visual social stimulation. In addition, growth of social females lagged behind that of isolates. Some mechanisms and biological effects are discussed.