Intersex Fish

      Biologists, over the past ten years, have been investigating fish kills in the Potomac River Basin . What the biologists found out was that male fish had female eggs in their testes. “For the past decade, they have worked to unravel the story of what’s causing “intersex” fish, a phenomenon that has turned up in 100 percent of smallmouth bass sampled in some areas of the Shenandoah and in 50 - 75 percent of those tested at a number of other sites in the Potomac basin” (Blankenship 1).

Smallmouth Bass

      Outside the watershed, in less polluted areas, intersex abnormalities are seen in no more than 10 - 15 percent of smallmouth bass. The presence of characteristics of both sexes in a single organism is called intersex. Vitellogenin, which is normally found in the blood of female fish, is a precursor of egg yolk and has also been found in male fish. Research has shown that discharges from wastewater treatment facilities are linked to intersex fish. “Meanwhile, the severity of the intersex abnormality - such as more eggs in a male fish’s testes - was generally higher in samples taken from areas with significant wastewater discharges, basins with large amounts of agricultural land and areas with high densities of agricultural animals or poultry houses” (Blankenship 1). Long term exposure to pollutants is what is seen to be the cause of the pronounced female characteristics found in male fish.

      “Intersex is caused by endocrine disruptors, which affect the hormone systems in fish, animals and humans. They are found in products intended to have biological effects, such as hormones or other feed supplements fed to livestock, or medicines taken by humans” (Blankenship 2). Although intersex characteristics have been found mainly in smallmouth and largemouth bass, it is occasionally found in other species. There are suspicions that chemicals are causing intersex and are resulting in the suppression of the immune systems of fish. This leads to fish kills due to fish being more susceptible to disease.

Largemouth Bass

      Though more research is needed to find the cause of intersex. I believe it is obvious that runoff from wastewater treatment plants and farm chemicals are causing intersex in fish. Fish with intersex characteristics are mainly found near wastewater facilities and near farming areas. Research should also delve into what can be done to decrease the exposure of chemicals to fish and other species.

Works Cited

Blankenship, Karl. Intersex fish linked to areas with high ag, wastewater runoff.

     Chesapeake Bay Journal, October 2012. Web, 10 October 2012.