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The Leavenworth Times - Leavenworth, KS
  • Matt Nowak: Are they boy or girl fish? It’s now harder to tell

  • According to the US Geological Survey, intersex, the presence of both male and female characteristics within the same fish, is being observed in fish in more streams across the nation.


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  • According to the US Geological Survey, intersex, the presence of both male and female characteristics within the same fish, is being observed in fish in more streams across the nation.
    Intersex is one manifestation of endocrine disruption in fish, which can also result in adverse effects on the development of the brain and nervous system, the growth and function of the reproductive system, and the response to stressors in the environment.
    The two major American fish species being studied are smallmouth and largemouth bass. In South Carolina, in the Pee Dee River, for example, 91 percent of male largemouth bass had female parts along with 60 percent of males in the Apalachicola River in Florida and 50 percent in the Savannah River in Georgia.
    The scientists do not know which chemicals are responsible for the endocrine disruption and suspect that it may be a combination of many of the chemicals including legacy chemicals like DDT, PCB’s, and mercury plus other chemicals from farm fields and sewage treatment plants.
    They do know that the incidence of affected fish is concentrated at points where there are heavy agricultural inputs and near human concentrations associated with sewage treatment plants. There is nothing to implicate any particular chemicals or environmental conditions that might cause the higher rates in some places, according to the studies, and it is not clear why bass might be especially prone to intersex conditions.
    “The occurrence was more widespread that we anticipated,” said Jo Ellen Hinck, a biologist with the USGS. “When you have the majority of fish at a site showing up intersex, that’s worrisome. We think that’s enough reason to try to find out what’s the cause of this and if it has implications for ecosystem health.”
    While the Yukon River was the only basin that appeared to be free of intersex fish, the condition was extremely common in the Southeast and particularly in largemouth bass. “Fish aren’t the only animals whose hormonal systems appear to be going haywire, there is growing evidence for similar conditions in birds, mammals and people,” according to the scientists.
    Further study showed abnormal levels of vitellogenin in smallmouth bass. It is a protein produced by female fish to form egg yolk and is normally absent in males. In these studies, males had abnormal levels of vitellogenin while females had a substantial decrease in the protein, thereby, also disrupting their egg production.
    They found female germ cells in the testes of as many as 100 percent of the male smallmouth bass collected downstream from sewage treatment plant outfalls. There was also more than a tenfold decrease in the concentration of vitellogenin from females compared to those collected from 10 miles above the treatment plant.
    I suspect that some folks do not consider humans to be directly related to all the other animals and so for them, this may not be an issue of any importance.  For the rest of us who think of humans as animals, you have to wonder what effect our water supply is having on us, especially if it is coming from surface sources like our rivers that also support large human communities who discharge their wastes into the rivers.
    Page 2 of 2 - It is not uncommon to read about women who are having difficulty becoming pregnant. We are not fish and I do not know enough about our human endocrine system to know whether a contaminated water supply has a negative effect on our reproductive system, our brains, and the rest of our nervous system.
    It is enough to make you wonder about how our wastes, both chemicals at home and from agriculture, could affect our human bodies. Heck, it’s enough for me to wonder if it is OK to even eat a bass.  Maybe it is better to just catch and release all the bass.
    Matt Nowak lives in Lansing and works as a natural resources manager.
     

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