Uncertainty returns over sex-change fish

Last year, scientists thought they’d found out why female fish in some paper-mill–polluted Florida rivers look like males (SN: 1/6/01, p. 8: Macho Waters). They’d discovered androstenedione, a male hormone and a precursor to testosterone, in the water.

Androstenedione probably formed from pollutants and then became concentrated enough to affect the fish, the researchers said.