From CNN.com and other sources

   When exposed to low level of synthetic estrogen, the fertility of a mature male rainbow trout decreases by as much as 50 percent. This chemical substance is in surface waters around the world. Estrogen and other hormones make their way into water via sewage-treatment plants and septic systems. The EPA is studying which hormones have harmful effects on fish's reproduction and will debate it at an emergency pollutant workshop.