News: Study links population to intersex fish
Ye Old One
Fri Feb 8, 6:13 PM ET
http://news.yahoo.com/s/ap/20080208/ap_on_sc/intersex_fish_2
BALTIMORE - A form of intersex fish, which have both male and female
traits, were found more often by researchers in areas with more
farming and population density, according to a new study by the U.S.
Geological Survey.
So-called intersex fish have been found in U.S. waters over the past
decade, including the southern Great Lakes, the Potomac River
watershed, which includes the Eastern Panhandle in West Virginia, and
the Southern California coast. The cause isn't fully understood, but
researchers suspect wastewater and farm runoff polluted with chemicals
that stimulate estrogen production are at fault.
U.S. Geological Survey researchers found the frequency of male
smallmouth bass with immature female eggs in their testes was highest
where farming is most intense and where human population density is
highest. The study also found the prevalence of the form of intersex,
known as testicular oocytes, was greatest just before and during the
spring spawning season.
The results were published in the current edition of the Journal of
Aquatic Animal Health.
USGS scientist Vicki Blazer, who led the study, said smallmouth bass
were collected from the Shenandoah River, the South Branch of the
Potomac, and the Potomac River basin.
"On the Shenandoah, rates of intersex were highest, ranging from
80-100 percent intersex," Blazer said.
In the Potomac basin, 75 percent of fish had testicular oocytes in the
most heavily farmed and populated areas, dropping to 14 percent to 35
percent in less farmed and developed sites.
In the South Branch, percentages ranged from 47 percent to 77 percent,
increasing along with farming and population, the researchers said.
Last year, the Sierra Club asked the Environmental Protection Agency
to ban the use of certain toxic chemical compounds in industrial and
household detergents because the ingredients are believed to cause
male fish to develop female characteristics. The Sierra Club also
asked the Environmental Protection Agency to bar the use of these
products in areas where wastewater treatment plants aren't equipped to
remove nonylphenol ethoxylates, or NPEs.
The compounds, derived from petroleum, are used mainly in detergents
but also in paper manufacturing and flame retardants.
NPEs are more tightly restricted in Canada and Europe than in the
United States, which issued water-quality limits for the key
ingredient, nonylphenol, or NP, in December 2005. Detergent
manufacturers Procter & Gamble of Cincinnati and Unilever have
substituted other chemicals in their products, and Wal-Mart is seeking
to phase NPEs out of its stores by rewarding companies that find
alternatives.
--
Bob.