Bass fish in US rivers have become bisexual

This is due to the use of chemicals in the detergent industry, which have been banned in Europe and Canada

Androgynous fish, showing external signs of both males and females, have often been found by researchers in areas of dense population or massive particle activity. This is according to a study by the US Geological Survey.

The transsexual fish were found in many bodies of water in the USA in the past decades, including in the Great Lakes, in the Potomac Basin, including in parts of it in West Virginia, as well as on the coast of Southern California. The cause of the problem is unknown, but researchers suspect that urban and agricultural wastewater is contaminating the water with chemicals that encourage estrogen production.

Geological Service researchers found that in the bodies of male smallmouth bass, there were unfertilized and undeveloped eggs as females have, and their testosterone level is high - in areas where the human population is particularly dense. The study also found that the chance of bisexual fish from the type known as testicular oocytes was highest just before and during the spring spawning season.

The results were published in the latest issue of the journal Aquatic Animal Health.

Vicki Blazer, the study's lead researcher, said the bass were collected from the Shenandoah River, a southern tributary of the Potomac, and the Potomac River Basin itself. In the Shenandoah River, the rate of bisexual fish was high, 80-100 percent," said Blazer. In the Potomac Basin itself, 75% of the fish had testicular oocytes - mainly in farm areas and populated areas, and the rate dropped to 14-35% in less populated areas and not near large farms.

In the southern channel, the proportion of bisexual fish varies between 47 and 77% depending on the density of the population and the farms.
About a year ago, the Sierra Club petitioned the Federal Environmental Protection Agency to ban the use of several chemical compounds in household and industrial cleaners because they believe these ingredients cause male fish to develop female characteristics. The Sierra Club also demanded that the EPA limit the use of these products in areas where wastewater treatment plants are not equipped to remove nonylphenol ethoxylates (NPE). The compounds, derivatives of petroleum, are used mainly in cleaning agents but also in the paper industry and in the materials found in fire extinguishers.

The use of NPE compounds is restricted in Canada and Europe to a greater extent than in the US, where only the use of nonylphenol (NP) has been restricted since December 2005. Detergent manufacturers Procter & Gamble and Unilever have replaced the substance with other chemicals in their products, and the Walmart marketing chain is looking for ways to remove the NPE from its stores by encouraging companies to find alternatives.

Previous news on the subject

Fish stories - fish change their gender because of birth control pills

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