Even after being treated, wastewater is causing some male fish to lose their sexuality and resulting in a crash in reproduction levels, according to a study by the National Water Research Institute in Ontario, Canada. The study adds to a recent barrage of evidence that fish are being harmed by trace levels of pollution flowing from sewage plants.
A five-month study of fathead minnows showed a 50 percent decline in reproduction among fish exposed to high levels of treated wastewater effluent. Male fish also exhibited a significant loss of secondary sex characteristics, the physical attributes that make them attractive to female fish, the likely explanation for a decline in egg production.
The Institute’s study was one of more than 20 presented at yesterday’s Society of Environmental Toxicology and Chemistry (SETAC) conference that focused on endocrine disruption – how chemicals, pharmaceuticals and personal care products that slip through wastewater treatment are affecting fish and marine life.
The fathead minnow data perplexed scientists because, aside from reproduction levels and physical characteristics in male fish, the sampled fish survived in wastewater at similar levels as a control group. But other studies, like one conducted by USGS, may link incidences of “intersex” – male fish exhibiting female characteristics and sex organs resulting from endocrine disruption – to fish kills. USGS scientist Vicki Blazer said incidences of intersex among small mouth bass populations on the South branch of the Potomac River are as high as 58 percent. The Potomac has witnessed a rash of small mouth bass kills in the last three years.
The Los Angeles Times reported this week that male fish with female characteristics have been found off the coast of California, and scientists suspect a link to hormone-disrupting chemicals found in sewage released into the ocean.
