Photograph by James Forester, USFWS
Bullhead Studies in the
and the Anacostia River are two of the three Regions of Concern in the
Chesapeake Bay, designations based on chemical contaminant concentrations
in sediments. Chesapeake Bay Field Office Environmental Contaminants Specialists
have conducted several studies with brown bullheads (Ameiurus nebulosus)
to determine if these contaminants are affecting the health of fish populations.
In 1996, biologists
collected four groups of brown bullheads from the tidal Potomac watershed
to look for tumors in relation to contaminant exposure. These bottom feeding
fish were collected from the Quantico embayment, near a Superfund site
which released polychlorinated biphenyls (PCBs) and DDT compounds; Neabsco
Creek, a tributary with petroleum inputs from upstream areas and marinas;
and the Anacostia River (both in spring and fall), where sediment is contaminated
with polynuclear aromatic hydrocarbons (PAHs), PCBs, and organochlorine
pesticides. A fifth group was collected from the Tuckahoe River on Marylands
Eastern Shore as a reference. Fish were examined for liver and skin tumors.
Fifty percent of
Anacostia fish caught in the spring and 60% of those caught in fall had
liver tumors compared to 17% from Neabsco Creek, 7% from Quantico and
10% from Tuckahoe River. Biologists also found that 37% of Anacostia fish
caught in spring and 10% of those caught in fall had skin tumors compared
to only 3% from Neabsco Creek and Quantico and none from Tuckahoe River.
The number of Anacostia fish with tumors is similar to those at contaminated sites in the Great Lakes and warrants concern. PAH concentrations were significantly higher in Anacostia sediments than at the other sites. At present, there are insufficient data, however, to establish a cause and effect link with a particular class of contaminants. Chesapeake Bay Field Office recommends using tumor studies to monitor the health of resident fish and as a tool to evaluate the success of clean up efforts.
In 1998, bullheads
were collected near Baltimore Harbor from Furnace Branch, a tributary
to the Patapsco River, and Back River to study tumor prevalence near this
urban area.. Bullheads were also collected from the Tuckahoe River as
a reference. Data analyses are in progress.
The use of the brown
bullhead as an environmental indicator requires that scientists have an
understanding of fish movements so that the exposure area can be estimated.
Chesapeake Bay Field Office Environmental Contaminants Specialists, in
collaboration with Dr. Roman Jesien of the University of Maryland Eastern
Shore, are using ultrasonic transmitters to track the movements of bullheads
in the Anacostia River. This study is in progress..