Sterilization of fish by high temperature

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Juveniles of the Mozambique tilapia, were reared from 3 days after hatching at a high temperature (37 degree centigrade) for 50 days. The gonads of all individuals were sterile. Sterile females did not display sexual behavior or exhibit female nuptial coloration, Histological analysis revealed the absence of all stages of spermatogenic germ cells from the testes of the heat-treated males; however, structures within the layer of epithelial cells lining the efferent ducts were observed to be actively secreting sperm fluid into the ducts, as also seen in the mature testes of normal males. The sterilized males nonetheless displayed male nuptial coloration, actively dug spawning nests, and mated with normal mature females. However, females mated with these males initially brooded their eggs normally but released them prematurely at 4 to 5 days. All the released eggs were unfertilized, and all were dead.