A survey of fish in rivers and streams around the country shows that a large percentage of male bass have acquired feminine characteristics. Scientists say it's the biggest survey of this gender-bending condition in U.S. waters. And while they can't be sure of the cause, they suspect industrial and pharmaceutical chemicals are the culprit.

Male fish with female body parts have been showing up in our nation's rivers for a while now, but a new study found a surprising number of mixed-up fish.
From the Mississippi to the Rio Grande, from the Appalachia to the Colorado, researchers found large numbers of river fish with egg cells in their testes, particularly in two species: smallmouth and largemouth bass.

The nation's fish -- particularly two species popular with anglers -- are facing a widespread and ill-defined threat that is blending their genders. In the most comprehensive study to date -- of 16 species in nine river systems over nine years -- government scientists have for the first time documented the surprising pervasiveness of so-called intersex fish.

Sexual deformities in smallmouth and largemouth bass are more widespread than previously thought in river basins across the country, including the Columbia River basin in the Northwest.

A new study released Monday finds surprisingly high incidences of male fish carrying immature eggs in their testicles. The “intersex” fish are appearing throughout the nation, including in western Colorado. The study did not examine why the aquatic hermaphrodites were so prevalent in the nation’s waterways, though lead author Jo Ellen Hinck suggested it was unlikely any one human activity or contaminant was responsible. She added that far more research would have to be conducted before any reliable assertions could be made on the matter.

Male bass in Colorado rivers and other basins around the nation widely exhibit feminine sex traits, a federal fish study released Monday shows. This gender-bending was most common in the southeastern U.S. as well as in western Colorado, in the Yampa River, where 70 percent of male bass had eggs developing alongside their testicular organs, the U.S. Geological Survey study found.

Government scientists figure that one out of five male black bass in American river basins have egg cells growing inside their sexual organs, a sign of how widespread fish feminizing has become. The findings come from the U.S. Geological Survey in its first comprehensive examination of intersex fish in America, a problem linked to women's birth control pills and other hormone treatments that seep into rivers. Sporadic reports of feminized fish have been reported for a few years.

Of the 16 fish species researchers examined from 1995 to 2004, the condition was most common by far in smallmouth and largemouth bass: a third of all male smallmouth bass and a fifth of all male largemouth bass were intersex. This condition is primarily revealed in male fish that have immature female egg cells in their testes, but occasionally female fish will have male characteristics as well.

Intersex in smallmouth and largemouth basses is widespread in numerous river basins throughout the United States is the major finding of the most comprehensive and large-scale evaluation of the condition, according to U.S. Geological Survey (USGS) research published online in Aquatic Toxicology.

A U.S. Geological Survey study has found intersex in smallmouth and largemouth bass to be widespread in numerous U.S. river basins. USGS scientists said their finding is the result of the most comprehensive and large-scale evaluation of the condition, which is primarily revealed in male fish having immature female egg cells in their testes, and occasionally female fish with male characteristics as well.

The agency looked at past data from nine river basins - covering about two-thirds of the country - and found that about 6 percent of the nearly 1,500 male fish had a bit of female in them. The study looked at 16 different species, with most not affected. But the fish most feminized are two of the most sought-after freshwater sportfish: the largemouth and smallmouth, which are part of the black bass family. Those two species were also the most examined with nearly 500 black bass tallied.

Government scientists figure that one out of five male black bass in American river basins have egg cells growing inside their sexual organs, a sign of how widespread fish feminizing has become. The findings come from the U.S. Geological Survey in its first comprehensive examination of intersex fish in America, a problem linked to women's birth control pills and other hormone treatments that seep into rivers. Sporadic reports of feminized fish have been reported for a few years.

Intersex in smallmouth and largemouth basses is widespread in numerous river basins throughout the United States, is the major finding of the most comprehensive and large-scale evaluation of the condition, according to U.S. Geological Survey (USGS) research published online in Aquatic Toxicology.
Contact: Jo Ellen Hinck at 573-876-1808 or jhinck@usgs.gov
CERC Pub Brief

Intersex in smallmouth and largemouth basses is widespread in numerous river basins throughout the United States is the major finding of the most comprehensive and large-scale evaluation of the condition, according to U.S. Geological Survey (USGS) research published online in Aquatic Toxicology. Of the 16 fish species researchers examined from 1995 to 2004, the condition was most common by far in smallmouth and largemouth bass: a third of all male smallmouth bass and a fifth of all male largemouth bass were intersex. This condition is primarily revealed in male fish that have immature female egg cells in their testes, but occasionally female fish will have male characteristics as well.

USGS scientist Duane Chapman provided reporters and filming crew from National Geographic an educational Missouri River tour for the upcoming winter television special, "Monster Fish," which profiles invasive Asian carp. Chapman explained the carps' invasive history, the abundance of larvae compared to native fish, and why their anatomy makes carp such a fierce competitor. National Geographic will return in Sept. for more details on Asian carp research underway at the USGS Columbia Environmental Research Center.

USGS scientist Chris Ingersoll was interviewed and appeared on KOMU TV, Columbia, Mo., on July 30, 2009. The interview was about a biosolids spill along Missouri Callaway County Road UU, south of Columbia, due to a traffic accident. Dr. Ingersoll gave information regarding the transport and safety of biosolids, stating that this spill was not a hazard to the public.

Aaron DeLonay, an employee for the Columbia Environmental Research Center, shows David Walchshauser a shovelnose sturgeon on California Island during the Big Canoe River Float on Saturday. Many of the sturgeon in the Missouri River are electronically tagged and monitored because of their status on the endangered species list. Sturgeon were around with the dinosaurs and many found in the river are more than 15 years old.

USGS scientist Duane Chapman of the Columbia Environmental Research Center, appeared on June 7, 2009, in the Columbia Missourian about Asian carp facing starvation and reproductive problems in the Missouri River. Chapman discussed their health decline, which is hypothesized to result from a low supply of zooplankton in the river.

The American Society for Photogrammetry and Remote Sensing (ASPRS) just notified the winners of its prestigious 2009 Boeing Award for Best Paper in Image Analysis and Interpretation. The award was given to USGS scientist Matthew Struckhoff, Columbia Environmental Research Center, and his co-authors, for the article entitled, "Mapping Vegetation Communities Using Statistical Data Fusion in the Ozark National Scenic Riverways, Missouri, USA," which appeared in the February 2008 issue of the journal. The ASPRS advances knowledge of mapping sciences through imaging and geospatial information, a professional, international society.

Exactly how the chemicals are able to transform males into females is the subject of continuous study. "There are several hypotheses about how a genetically male frog can become a phenotypic female frog or an intersex frog." Papoulias adds. "Most involve interference by the chemical [endocrine disruptor] on the sex steroids."

A new website by the U.S Geological Survey focuses on the science and natural resources of the Ozarks and makes that information available to the public. Officials say the website was designed to inform the public about the natural and cultural resources of the Ozarks, while also facilitating the exchange of information. Ozarks at Large's Bryan Rachal has the story.

news release: Ozark Natural Resource Information Now Available Online

"I don't think there are very many serious scientists who think it could have been native to Montana," said Duane Chapman, president of the Introduced Fish Section in the American Fisheries Society, a leading organization of fisheries professionals. Walleye "have been moved around an awful lot through illegal stocking," Chapman said from Columbia, Mo. The fish is found widely in the United States.

Duane Chapman