Effect of methallibure on gonad development and carotenoid content of the fins of Sarotherodon mossambicus (Tilapia mossambica)

Juvenile Sarotherodon mossambicus were exposed to a daily dose of 1 or 2 p.p.m. of the antigonadotropic drug methallibure for a period of seven weeks. The control fish all showed well-developed gonads and a considerable concentration of astaxanthin in the dorsal fins. The dominant male showed a much higher astaxanthin value than the other fishes. Methallibure completely prevented gonad development. Nevertheless, some astaxanthin deposition did occur in the drug-treated fish.