Aquaculture Crsp 21st Annual Technical Report

All-male tilapias are desirable because they manifest superior growth characteristics compared to females. The synthetic steroid, 17α-methyltestosterone (MT) has been commonly used to sex-reverse tilapia but because of its potential health and environmental hazards, the use of phytochemicals as alternative means to affect sex differentiation has to be explored. We addressed objective 1 by using the high performance liquid chromatography (HPLC) technique to determine MT concentrations in the water and in fish. We determined the rate of excretion/degradation of MT following dietary uptake. We addressed objective 2 by examining the dietary intake of quercetin, genistein, and complex of flavonoids in the form of maca meal or “propolis”. The phytochemicals that we tested in this study showed potential for affecting sex ratios although their potency was lower compared to MT. Further studies are needed to evaluate other phytochemicals that contain flavonoids and/or isoflavonoids and how these substances are metabolized.