TODAY IS Monday, December 29 , 2003
Delaware's striped bass studied for infection
By MOLLY MURRAY
Sussex Bureau reporter
12/29/2003
A team of scientists is trying to determine whether striped bass in
Delaware Bay have been infected with a disease that has been
widespread in the Chesapeake Bay, making the fish hard to sell and
creating mild health risks for people who handle the fish.
The infection, called mycobacteriosis, causes sores on some of the
bass, while attacking the internal organs of other seemingly healthy
fish.
Scientists who have studied the disease in bass in the Chesapeake
Bay don't know whether the disease kills fish, but are worried that
the bacteria could devalue an important fishery along the Atlantic
Coast from the Chesapeake Bay to Long Island. Infected fish are
thinner than normal and the sores make them unsightly.
In 2002, the dockside value of the striped bass harvest from
Delaware's commercial fishermen was more than $350,000, said Roy
Miller, the state fisheries administrator. The state does not
estimate the recreational value of striped bass, but it is
significant for businesses that sell bait and tackle and for boat
charters. Weekend fishermen prize striped bass because of their
size, fight and taste.
The disease also concerns scientists because it could threaten a
striped bass population that has made a comeback after a decline
required a fishing moratorium in the mid-1980s to allow stocks to
rebuild. This year, the juvenile striped bass population was
estimated to be at its highest level since 1980, Miller said.
Striped bass also are important predators that keep other fish
species in check, said Chris Ottinger, a research fisheries
biologist with the U.S. Geological Survey's National Fish Health
Laboratory in West Virginia.
The disease is not a threat to people who consume the bass, but one
form can be passed to humans and cause a skin infection called "fish
handler's disease." Researchers have recommended that people who
regularly handle the fish wear gloves and heavy boots, avoid
exposing cuts or scrapes to the water and wash with a disinfectant.
The study of striped bass from the Delaware Bay is aimed at
assessing the spread of the disease and seeing whether local fish
are less susceptible to the bacteria. A study also is planned in the
Long Island area.
Striped bass are migratory and are found along the Atlantic Coast
from the St. Lawrence River in Canada to the St. Johns River in
Florida. Delaware officials said studies have shown that hundreds of
Delaware Bay stripers move through the Chesapeake & Delaware Canal
and are caught by Chesapeake Bay anglers.
"Clearly our fish are going over there," Miller said.
So far, cases of striped bass with lesions in Delaware waters have
been rare, Miller said. A catch of 15 fish at Woodland Beach earlier
this month found no signs of the disease.
Two striped bass with lesions were brought to state officials in
recent years for testing. One was caught in the Nanticoke River,
which flows into the Chesapeake Bay, and the other in Indian River,
which flows into Indian River Bay, Miller said.
There is enough concern about the disease that some Delaware seafood
dealers, including Jeanie Harper, the owner of Dawson's Seafood on
Madison Street in Wilmington, refuse to sell or handle striped bass
caught in Chesapeake Bay.
Harper said she noticed about three years ago that Chesapeake
striped bass were thinner and some had sores. She contacted Maryland
officials, who referred her to a researcher at the University of
Maryland.
"He said the danger is to the fish and the fish handler," Harper
said. "At that point, I said, 'I'm not handling this fish.' ''
She has been buying her striped bass from Delaware fishermen this
year.
"We didn't see any disease," she said. "The fish were beautiful."
The fish infection started showing up in wild striped bass in 1998
when Maryland scientists were investigating a large fish kill in the
Pocomoke River that was linked to the sometimes toxic microbe
pfiesteria.
As many as 70 percent of the striped bass in the Chesapeake Bay may
now be infected, according to the U.S. Geological Survey. About 15
percent of the striped bass caught by fisheries scientists have the
external skin sores, said Phil Jones, a fisheries resource manager
with the Maryland Department of Natural Resources.
For the Delaware Bay study, the U.S. Fish & Wildlife Service and
U.S. Geological Survey have joined commercial fishermen to set nets
and gather fish at two locations: Woodland Beach near Smyrna and
Bowers Beach south of Dover. The goal is to get 50 fish from each
location.
The study will assess striped bass health in the Delaware River and
Bay, looking for any indicators of a problem. Scientists also will
look for differences in the local fish stock that might explain why
it has not shown up. Blood samples collected from Delaware Bay fish
may be able to tell scientists whether the local stock has
antibodies that protect bass from the infection.
They also hope to identify the genetic stock that is typical in
Delaware Bay because different stocks of fish have different disease
resistance, Ottinger said.
Some researchers think Chesapeake Bay stripers may be vulnerable to
the naturally occurring bacteria because of limited food sources or
environmental conditions. In fish farms, the disease is typically
associated with high-stress environments for the fish.
Some scientists think one factor may be a decline in menhaden, once
a major food source for striped bass. Others think low oxygen levels
in the bay may be causing stress in the population.
Reach Molly Murray at 856-7372 or mmurray@delawareonline.com.
The News Journal/SCOTT NATHAN
Fishermen Mark Craven, Leonard Voss and Larry Voss, all of
Smyrna, help study striped bass off Woodland Beach.
Aquatic ecologist Holly Weyers (left) and fishery biologist
Clif Tipton unload bass caught early this month in Delaware
Bay.
The News Journal/SCOTT NATHAN
Chris Ottinger, a biologist with the U.S. Geological Survey,
cuts open a fish caught in Delaware Bay to check for signs of
bacterial infection.
ABOUT STRIPED BASS
LATIN NAME: Morone saxatilis
COMMON NAMES: Rockfish, rock, striper
RANGE: Atlantic Coast from St. Lawrence River in Canada
to St. Johns River in Florida. Most common from Maine to
North Carolina.
STOCKS: The East Coast migratory population includes
three major stocks: the Hudson in New York, the
Chesapeake in the Delmarva region and the Roanoke along
the Carolinas.
HABITAT: Most spend summer and early fall in middle New
England close to shore. During the late fall and early
winter, coastal striped bass migrate south to winter off
the North Carolina and Virginia capes. The fish move to
tidal fresh water to spawn. In the Delaware River, the
key spawning area is at Cherry Island Flats, near
Wilmington. The spawning area extends north to the
vicinity of Philadelphia International Airport.
OF NOTE: The largest recorded striped bass weighed in at
125 pounds and was caught in North Carolina in 1891. The
Delaware record is 51 pounds, 8 ounces, caught in 1978.
ABOUT THE INFECTION
Mycobacteriosis causes sores on some striped bass and
attacks the internal organs of other seemingly healthy
fish.
Scientists don't know whether the disease kills fish.
The disease is not a threat to people who eat the bass,
but one form can give people a skin infection called
"fish handler's disease."
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