Canadian researchers who studied fish in Alberta’s Red Deer and Oldman rivers found a peculiar effect of pollution on a native minnow called the longnosed dace. Males they sampled contained elevated levels of a protein marker normally only found in females. Also, “…up to 44 per cent of the male fish had eggs in their testes.” In normal circumstances only females produce eggs. One of the study’s co-authors Lee Jackson said, “… it tells us the fish are exposed to estrogen or something that looks like estrogen to the fish.” Mr. Jackson is the executive director of a research facility which creates new approaches for treating wastewater.
The researchers also analyzed water samples from the river locations where they examined the minnows. They found synthetic estrogens from birth control pills and hormone therapy drugs in the river water. In addition, synthetic and natural hormones were found in the water, which could be from agricultural run-off and cattle ranching. The researchers took samples at 15 locations along 600 kilometers of river. Their study indicated the disruptive chemicals could be present in a span covering the entire 600 kilometers of river water.
The ratio of females to male minnows in the rivers could also be shifting much toward greater numbers of females. If this ratio remains unbalanced, fewer numbers of new fish will be born, as there will not be enough males to fertilize fish eggs. With so many chemicals in the minnow’s habitat, it could be difficult to pinpoint exactly which chemical is causing the gender bending, or if it is a combination of all of them.
The effect, called fish feminization, is not unique to the Alberta minnows. In fact, it has been documented in Europe, and the United States as well.
The Canadian researchers are going to continue their studies to deepen their knowledge of what is taking place in the Red Deer and Oldmans rivers, with the ultimate goal of perhaps influencing policy decisions that can stop the problem.
Longnosed dace eat aquatic insects and are prey for larger fish, so they are an important part of the food chain.
Recently in Colorado a similar situation was partly remedied by upgrading a wastewater treatment plant. Fish exposed to the water previously had been feminized in about seven days, but after the treatment plant’s upgrade, it took more than 28 days.
One of the researchers involved in the Colorado study said that it is not only about changing wasterwater technology, it is also about modifying consumer behavior, “We excrete natural and synthetic estrogens and use shampoos, detergents and cosmetics containing a variety of hormone disrupters that wind up in waterways. All of these different chemicals we are putting into the environment have the potential to alter the biology of animals and to affect ecosystems.”
He said consumers can refuse to buy milk made with growth hormones and antibacterial soaps. Also they can reduce their use of shampoos and detergents.
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