Gender Bender Fish

The entire male fish population of some European rivers have changed, or are changing, from so-called “gender-bending” chemicals, according to new research.

Freshwater fish in five out of seven northern European countries surveyed so far showed some signs of exposure to the chemicals, which mimic female hormones and are present in sewage effluents. When addressing the British Association’s Festival of Science in London Professor Alan Pickering of the Natural Environment Research Council’s Centre for Ecology and Hydrology, UK, said, “We are finding this problem right across northern Europe, it is clearly widespread.”

“It seems to relate to a mixture of chemicals both industrial and also some of the natural excretory products from the human body.”

Symptoms of exposure to the chemicals, known as endocrine-disrupters, ranged from relatively minor effects to, in the worst cases, fish developing both male and female reproductive organs.

In some places, such as the River Aire, Yorkshire, UK, 100% of male fish were found to show evidence of feminisation.

Professor Pickering said it was still not clear whether the chemicals were having a direct impact on the ability of fish to reproduce normally. But in one UK river at least, he said, detrimental effects had been established.

This has raised concern that predators that eat the fish, such as otters and kingfishers, could also be at risk.

“We don’t know how serious an environmental issue this is, “Professor Pickering said. “If there is a serious impact on fish populations, we should be worried about it.”

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