Chesapeake Bay's Ecology Linked To Atlantic Menhaden
The declining forage base for larger predator species, such as striped bass, bluefish and weakfish
in the Chesapeake Bay, has raised concern about the percentage of Atlantic menhaden that are
being harvested from the Chesapeake Bay. During the 1997 summer and fall season, large
numbers of adult male striped bass over 18" were exhibiting signs of poor nutrition and starvation.
The Atlantic coast menhaden population has declined 58% since 1991, while landings in
the Chesapeake Bay have remained relatively high averaging 150,000 metric tons per
year and actually increased to approximately 160,000 metric tons in 1997. Approximately
60 percent of the total landings for the entire east coast were harvested from Virginia's
portion of the Chesapeake Bay during the 1997 season. Atlantic menhaden are an extremely
important link in the coastal marine food chain, transferring enormous amounts of nutrients into
forage biomass and at the same time, improving water quality in the Chesapeake Bay. No other
fish has the capability to replace this unique species that can filter the plankton from more than a
million gallons of water in 180 days. The Chesapeake Bay Acid Rain Foundation, Inc. is currently
working with representatives from the Chesapeake Bay Program, Maryland Department of Natural
Resources, Virginia Marine Resources Commission, National Marine Fisheries Service and U.S.
Fish and Wildlife Service. A workshop to investigate living resources and water quality monitoring
data, that are showing declining or degrading trends in the Chesapeake Bay and its tributaries, is
being sponsored by the Science and Technical Advisory Committee of the Chesapeake Bay
Program on July 8 & 9, 1998.
The Atlantic States Marine Fisheries Commission's Atlantic Menhaden Fishery Management Plan
(FMP) established 6 trigger variables to represent different biological aspects to use in reviewing
the status of the Atlantic menhaden stock. Data from 3 of the 6 trigger variables indicate why the
stock is not healthy. Landings are monitored to help determine if there is a change in stock
abundance. The 1997 total numbers landed have declined 68% since 1991. The Proportion of
Adults (Age-3+), in the landings are also monitored, the 1997 estimated value of 29.9% adult
menhaden exceeds the trigger value of 25%, and is the highest in 35 years. One of the most
important triggers are the Recruits to Age-1, the estimate for 1997 of 1.4 billion Age-1 menhaden
falls below the trigger value of 2.0 billion and the recent 3 year running average of 1.9 billion is also
below the trigger value. Population estimates for Age-1 Atlantic menhaden for 1996 and 1997 are
the lowest in 26 years, and the exploitation rate has increased from 29% in 1993 to 37% in 1997.
According to the FMP, a major concern raised by this variable is that several poor recruitment
years may occur consecutively, "such a situation, coupled with high fishing mortality, will
subsequently result in reduced spawning stock biomass, and potential recruitment overfishing".
"Because most of the harvest is of young, sexually immature fish, which could provide a greater
yield if harvested when older and larger, Atlantic menhaden are growth over-fished". Under
Section 3.2.1 of the FMP the Atlantic menhaden stock was considered severely depressed
from 1964 through 1968, when the population average was 4.65 billion fish, the estimated
population of 4.55 billion fish for 1997 is lower than the 5 year average for the mid sixties.
This situation should be of major concern to the ASMFC because the stock is continuing
to decline. The National Marine Fisheries Service should reduce the harvest of Atlantic
menhaden in the Chesapeake Bay and along the Atlantic coast until a significant improvement in
reproduction occurs and the population increases to a healthy level that will benefit the
commercial fishing industry as well as the many species of birds, mammals, and fish that depend
on this valuable resource. The ecology of the Chesapeake Bay and the entire Atlantic coast
depend on a large, healthy population of Atlantic menhaden.
For additional information contact:
CHESAPEAKE BAY ACID RAIN FOUNDATION, INC.
www.chesbay.org
410-822-9150/410-822-3697-Fax / E-Mail: staff@chesbay.org
Posted 8/19/98