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California’s Gender-Bending Fish Was Actually Just a Contamination Accident

Scientists thought male fish, exposed to artificial hormones, were growing eggs. They weren’t

smithsonian.com

Researchers thought that male fish, affected by artificial hormones in waste water, were growing eggs. This turned out to not be true. Photo: eutropihcation&hypoxia

Just over seven years ago, scientists studying the effects of waste water on ocean fish came across a striking discovery: some male hornyhead turbot that lived off the coast of southern California seemed to be growing eggs, potentially in response to hormones in the waste water. As Environmental Health News explains:

The fish were collected in 2003 a few miles offshore in multiple locations as part of research to determine whether ocean life is harmed at the outfalls. At the time, 11 of 64 male turbot and sole caught near the outfalls were marked positive as having eggs, while none were found farther away. The locations fit the hypothesis that the estrogenic pollutants in the wastewater could alter fish sex organs. “All of them were near an outfall site so the pattern we saw made sense,” Bay said.

The news made headlines, but there was only one problem: follow-up research found that the male fish never actually had any eggs at all. Contamination was to blame for the apparent gender-bending turbots:

Steven Bay, head toxicologist at the government-funded research institution, said they apparently were “stray eggs.” Some of the females’ eggs apparently dropped onto the male fish tissues. Bay said he is unsure whether the cross-contamination occurred on the boat, where the turbot and sole were collected and dissected off Los Angeles, Palos Verdes Peninsula and Huntington Beach, or in the laboratory.

…Bay said he is unsure whether the cross-contamination occurred on the boat, where the turbot and sole were collected and dissected off Los Angeles, Palos Verdes Peninsula and Huntington Beach, or in the laboratory.

So, no males with eggs. But the idea that fish are reacting to hormone-disruptors in the water still holds, being supported by laboratory and field research conducted elsewhere in the world.

More from Smithsonian.com:

Genetically Modified Salmon Should Be Headed to a Plate Near You
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About Colin Schultz
Colin Schultz

Colin Schultz is a freelance science writer and editor based in Toronto, Canada. He blogs for Smart News and contributes to the American Geophysical Union. He has a B.Sc. in physical science and philosophy, and a M.A. in journalism.

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