[Pharmwaste] Widespread Occurrence of Intersex Bass Found in U.S. Rivers

DeBiasi,Deborah Deborah.DeBiasi at deq.virginia.gov
Mon Sep 14 13:14:40 EDT 2009

This release can be found in the USGS Newsroom at:

Widespread Occurrence of Intersex Bass Found in U.S. Rivers
Released: 9/14/2009 12:00:00 PM 

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192 Jo Ellen Hinck  
Phone: 573-876-1808 

Catherine Puckett  
Phone: 352-264-3532 



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.

Scientists found intersex fish in about a third of all sites examined
from the Apalachicola, Colorado, Columbia, Mobile, Mississippi, Pee Dee,
Rio Grande, Savannah, and Yukon River basins. The Yukon River basin was
the only one where researchers did not find at least one intersex fish.

Although intersex occurrence differed among species and basin, it was
more prevalent in largemouth bass in southeastern U.S., where it
occurred at all sites in the Apalachicola, Savannah, and Pee Dee river
basins, said Jo Ellen Hinck, the lead author of the paper and a
biologist at the USGS Columbia Environmental Research Center. The
researchers also documented intersex in channel catfish for the first

"Although the USGS has already documented the severity of intersex in
individual basins such as the Potomac, this study reveals the prevalence
of intersex is more widespread than anyone anticipated, said Sue
Haseltine, associate director for biology at the U.S. Geological Survey.
"This research sends the clear message that we need to learn more about
the hormonal and environmental factors that cause this condition in
fish, as well as the number of fish afflicted with this condition."

The study, said Hinck, presents the observed occurrence of intersex in a
variety of freshwater fish species, but not potential causes. "This
study adds a lot to our knowledge of this phenomena, but we still don't
know why certain species seem more prone to this condition or exactly
what is causing it. In fact, the causes for intersex may vary by
location, and we suspect it will be unlikely that a single human
activity or kind of contaminant will explain intersex in all species or
regions," she said.

For example, said Hinck, at least one of their sites with a high
prevalence of intersex-the Yampa River at Lay, Colo.-did not have
obvious sources of endocrine-active compounds, which have been
associated with intersex in fish.  Such compounds are chemical stressors
that have the ability to affect the endocrine system and include
pesticides, PCBs, heavy metals, household compounds such as laundry
detergent and shampoo, and many pharmaceuticals. Yet other study sites
with high occurrence of intersex were on rivers with dense human
populations or industrial and agricultural activities, which are more
generally associated with endocrine-active compounds.

"We know that endocrine-active compounds have been associated with
intersex in fish, but we lack information on which fish species are most
sensitive to such compounds, the way that these compounds interact to
cause intersex, and the importance of environmental factors," Hinck
said. "Proper diagnosis of this condition in wild fish is essential
because if the primary causes are compounds that disrupt the endocrine
system, then the widespread occurrence of intersex in fish would be a
critical environmental concern."

Specific river basin results include:

Intersex smallmouth bass were found in a third of male bass at almost
half of the sites examined in the Columbia, Colorado, and Mississippi
River basins.  The percentage of intersex smallmouth bass ranged from 14
to 73 percent at different sites. It was highest (73 percent) in the
Mississippi River at Lake City, Minn., Yampa River at Lay, Colo. (70
percent), Salmon River at Riggins, Idaho (43 percent), and the Columbia
River at Warrendale, Oreg. (67 percent).

Intersex largemouth bass were found in nearly a fifth of the fish
examined from the Colorado, Rio Grande, Mississippi, Mobile,
Apalachicola, Savannah, and Pee Dee River basins; intersex was not
observed in male largemouth bass from the Columbia River Basin. The
percentage of intersex largemouth bass per site ranged from 8 to 91
percent and was most prevalent in the southeastern United States. The
Pee Dee River at Bucksport, S.C., contained the highest percentage of
intersex fish (91 percent), with high percentages occurring elsewhere on
the Pee Dee too. Sixty percent of male bass examined at the Apalachicola
River at Blountstown, Fla., were intersex, 50 percent in the Savannah
River at Port Wentworth and Sylvania, Ga, 43 percent in the Savannah
River at Augusta, Ga., and 30 percent in the Chattahoochee River at
Omaha, Ga., and the Flint River at Albany, Ga. Lower percent intersex
(10-25 percent) were found in bass from sites in the Mobile River in

In addition, relatively high proportions of intersex largemouth bass
were observed at three sites in the lower Rio Grande Basin including Rio
Grande at Brownsville, Texas (50 percent), Rio Grande at Falcon Dam,
Texas (44 percent), and Rio Grande at Mission, Texas (20 percent).  In
addition, 40 percent of male largemouth bass from the Colorado River at
Imperial Dam, Ariz. and at the Gila River at Hayden, Ariz., in the
Colorado River Basin were intersex.

Deborah L. DeBiasi 
Email:   Deborah.DeBiasi at deq.virginia.gov (NEW!)
WEB site address:  www.deq.virginia.gov 
Virginia Department of Environmental Quality 
Office of Water Permit Programs 
Industrial Pretreatment/Toxics Management Program 
PPCPs, EDCs, and Microconstituents 
Mail:          P.O. Box 1105, Richmond, VA  23218 (NEW!) 
Location:  629 E. Main Street, Richmond, VA  23219 
PH:         804-698-4028 
FAX:      804-698-4032 

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