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USGS released today a national database and
report on endocrine and reproductive condition in two species of fish.
This is the first national database of endocrine information for fish collected
in U.S. streams and rivers. The information in the report provides a vital
national basis for comparison that will be used by scientists studying
endocrine disruption at individual sites across the country.
The database includes information on sex steroid
hormones, vitellogenin – an egg protein that indicates exposure to estrogenic
substances when found in male fish – and reproductive stage for common
carp and largemouth bass. Data summaries are provided by reproductive season
across a wide geographic scale.
From 1994-97, USGS researchers collected fish
(about 2,200 common carp and 650 largemouth bass) at 119 sites around the
country to determine levels of and variability in reproductive and endocrine
biomarkers, and to determine their potential utility in assessing reproductive
health and status in fish. The sites represented a wide range of important
streams and rivers across the United States; the sites also were characterized
by different land uses and levels of disturbance. Freshwater ecosystems
are the ultimate sink for many chemical contaminants, some of which can
alter endocrine and reproductive biomarkers of aquatic biota.
“Field studies of contaminants in aquatic
ecosystems frequently focus on local hot spots,” said Dr. Steve Goodbred,
a USGS scientist and lead author of the report. “Although such studies
have great value in understanding the occurrence of contaminants and possible
alterations in endocrine and reproductive biomarkers in fish, it is important
to acquire baseline information across large geographic areas to help establish
what is normal for that species at that season and in that region.”
Goodbred noted that the contribution of this
report is primarily in gathering information into a database that has great
potential for national-scale analysis and expansion as additional data
are collected. “Much of the information has been published piecemeal before,
but has never been aggregated into a database,” he said.
In the USGS study, common carp and largemouth
bass were collected during both non-reproductive and reproductive seasons.
Carp are a widely distributed bottom-dwelling fish whose feeding habits
expose them to many different types of environmental contaminants found
in water, sediments and food. Largemouth bass, a very important recreational
species, are also widely distributed but are predators and therefore are
exposed to different types of contaminants. Because of these differences,
carp and bass represent different kinds of “warning” sentinels of environmental
quality in aquatic ecosystems. Important aquatic ecosystems that were sampled
include the Mississippi and Columbia rivers, plus many other rivers including
the Colorado, Willamette, Potomac, Red River of the North, Platte, Hudson,
Missouri, and Connecticut.
The fish biomarkers measured in the USGS study
are important regulators of critical life history functions, such as egg
production, spermatogensis, fertilization, and development into sexually
mature fish. Other studies by USGS and other researchers have reported
correlations between specific reproductive impairment and elevated tissue
concentrations of environmental contaminants. Such changes include reduced
fertility, hatchability, viability of young, impaired hormone activity,
and altered sexual development and behavior. Abnormalities of these types
may be caused by alteration of normal endocrine function. |
