 A strange thing is happening to male smallmouth and largemouth bass swimming in waterways in parts of the Northeast: They are increasingly showing up with characteristics of the opposite sex. Fish and Wildlife Service encourages management actions that reduce runoff into streams, ponds and lakes -- both on and off of refuge lands.” The journal article, Evidence of estrogenic endocrine disruption in smallmouth and largemouth bass inhabiting Northeast U.S. National Wildlife Refuge waters: a reconnaissance study,” by L.R. It is tied to the exposure of fish to endocrine-disrupting chemicals that can affect the reproductive system and cause the development of characteristics of the opposite sex, such as immature eggs in the testes of male fish. Iwanowicz is the lead author of a paper on the phenomenon, which has been published in Ecotoxicology and Environmental Safety. Examples include some types of birth control pills, natural sex hormones in livestock manures, herbicides and pesticides. A 2009 study by the USGS examined 16 fish species from 1995 to 2004 and found a third of all male smallmouth bass and a fifth of all male largemouth bass were intersex. The USGS, which found intersex bass in the Columbia, Colorado and Mississippi river basins in 2009, calls it a "global issue" given changes that have been identified in locations worldwide. Chemical analyses of fish or water samples at collection sites were not conducted, so we cannot attribute the observation of intersex to specific, known estrogenic endocrine—disrupting chemicals.” This prevalence of intersex fish in this study is much higher than that found in a similar USGS study that evaluated intersex in black basses in nine river basins in the United States. And their grandchildren suffered a 30 percent decrease in their fertilization rate.
– Male bass are experiencing unwanted sex changes, apparently thanks to the "chemical soups" that pass for waterways in the Northeast. The Washington Post reports 85% of male smallmouth bass surveyed in the region have "characteristics of the opposite sex"—specifically eggs where their testes should be. The same is true of 27% of area largemouth bass, Vice adds. For a recently published study, researchers tested bass near 19 wildlife refuges in the Northeast, according to a US Geological Survey press release. Researchers didn't do a chemical analysis of the water where the intersex fish were found, so they can't be sure specifically what is causing the sex changes. But they suspect the problem is things that get dumped down drains and into US waters. Researchers believe the likely culprits are birth control pills, pesticides, hormones in livestock manure, and other chemical-heavy products, according to the press release. Vice reports those products contain estrogen, which can produce dramatic effects even at very low levels. But this isn't just a problem in the Northeast. Up to 90% of male smallmouth bass in parts of West Virginia are intersex, and increasing sex changes have been noted in nearly 40 fish species around the world going back 20 years, according to the Post. Study author Luke Iwanowicz calls these fish "the canary in the coal mine." "We are looking at fish but, of course, there is that concern that, if this stuff is in the water, it can be affecting other wildlife," he tells Vice. (A hermaphrodite cat got gender assignment surgery this year.)