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Menhaden Decline Threatens Bay Striped Bass Fishery

Chesapeake Bay Ecological Foundation, Inc. - January 5, 2007

The Atlantic menhaden decline along the East Coast of the United States has strong ecological significance and has raised interest and concern about how the nation’s fishery resources are being managed. Menhaden play an important role in the coastal food web and are crucial in the diet of many predators including Atlantic striped bass.

Recruitment overfishing (fishing pressure too heavy to allow a fish population to replace itself) combined with increased striped bass predation caused the menhaden stock to demonstrate signs of collapse during the 1960s and 2000s, periods of striped bass abundance. Over the past decade, the menhaden stock declined below the level needed to maintain its ecological role in the Chesapeake Bay and along the Atlantic Coast. The Atlantic States Marine Fisheries Commission (ASMFC), which is responsible for the management of Atlantic menhaden along the Atlantic coast, continues to state: “Menhaden are not overfished and overfishing is not occurring on a coastwide basis” because their modeling estimates indicate that the two overfishing targets in their Fishery Management Plan (FMP) have not been exceeded.

ASMFC’s single species management approach doesn’t take into account the importance of predator/prey relationships and their influence on productivity in the Chesapeake Bay. The Maryland Department of Natural Resources (MD-DNR) advised the ASMFC in 1998 of their concern that the low number of menhaden in Maryland’s portion of the Chesapeake Bay may be affecting the health of the bay’s striped bass population. Insufficient numbers of menhaden to support the nutritional needs of the Bay’s larger striped bass were first documented by studies in the early 1990s by Hartman and Brandt. In the late 1990s a study funded by MD-DNR and conducted over a larger portion of the bay by Anthony Overton, found that conditions had worsened and larger striped bass had altered their diet to include more bay anchovy and blue crab in order to survive. Striped bass health issues that included nutrition, lesions and disease were also documented in Overton’s study. Chesapeake Bay Ecological Foundation (CBEF) studies further demonstrate that reduced numbers of menhaden and bay anchovy in the Chesapeake Bay are having a negative impact on the growth and health of the bay’s juvenile and adult striped bass populations. CBEF has been conducting cooperative striped bass studies with the MD-DNR since the early 1980s and in 2004 initiated a Predator Prey Monitoring Program to determine the age structure of Atlantic menhaden consumed by large striped bass on the Atlantic coast and in the Chesapeake Bay. U.S. Fish & Wildlife Service, MD-DNR, East Carolina University and CBEF fund portions of the program.

CBEF first presented information concerning the decline of Atlantic menhaden and its effect on striped bass health to the ASMFC in 1997 at the request of the MD-DNR. This resulted in ASMFC conducting its first Menhaden Peer Review in 1998 which led to a revised FMP in 2001. A main objective of the new FMP was to reduce the impacts on species dependent on menhaden as prey. These species include important game fish such as bluefish, weakfish and striped bass. ASMFC has failed to achieve this objective. ASMFC’S menhaden stock assessment model uses age-specific fixed natural mortality rates that have not been adjusted for increases in predation mortality. As a result, ASMFC is unable to explain why their estimates of the total menhaden stock declined to record low levels while at the same time their fishing mortality estimates are at an all time low. Following a five year closure in Maryland’s portion of the Chesapeake Bay, ASMFC approved raising the striped bass minimum historical size of 12” to 18” for the Bay when the fishery reopened in 1990. By the mid-1990s the striped bass recovery had exceeded all expectations. This resulted in an unprecedented level of competition between the menhaden industrial fishery and high numbers of larger striped bass for the same size menhaden. Biologists have been concerned for years that the industrial fishery was already harvesting an excessive number of immature (ages 1&2) menhaden from the Bay. By 2006, the industrial menhaden harvest in the Bay, which is comprised of mostly immature menhaden, plummeted to its lowest level (approximately 150 million pounds) since the fishery first concentrated its efforts in the Bay 35 years ago. This was about half the average annual landings from the 1970s through the 1990s and approximately 75 million pounds below the 2006 Bay harvest cap adopted by the ASMFC.

Menhaden depletion has devastated the Chesapeake Bay striped bass population. The low number of immature menhaden is the result of increased competition between the industrial menhaden fishery, and the Bay’s larger/older migratory and resident striped bass. A 2006 – 2007 CBEF study found that both juvenile (less than 1 year old) and immature menhaden are now crucial to the health of the Bay’s striped bass because the minimum legal size of 18” resulted in an increase in the number of larger resident striped bass. For the first time since the industrial menhaden fishery concentrated its effort in the Bay during the 1970s, a major component of the Bay’s resident striped bass (larger/older fish) are competing with the industrial menhaden fishery for the same size immature menhaden. Historically, the Bay’s larger migratory striped bass have preyed on immature and adult menhaden during their fall and spring migration in and out of the Bay. Now declining numbers of both juvenile and immature menhaden are no longer capable of maintaining healthy striped bass populations in the Bay. Since the early 1990’s, recruitment overfishing dramatically reduced the number of large adult menhaden in northern coastal waters, caused low menhaden reproduction and disrupted the Bay’s ecosystem. This has affected the health of sub-legal striped bass in the bay which now weigh 30% less than their historic weight by the time they reach 18”. Striped bass growth has decreased and disease is a concern in the Bay because large numbers of striped bass are infected with mycobacteriosis. In 2006, CBEF examined 329 resident striped bass caught on charter boats in Maryland’s mid-Chesapeake Bay from July thru November and found only 5% exceeded 24”. The small percentage of large striped bass in the charter boat catch indicates that increased mortality has reduced the number of older striped bass in the Bay.

ASMFC decided to address menhaden depletion in the Bay by amending their FMP through the development of Addendum II, which included a Bay harvest “cap” option. They received about 25,000 responses during the public comment period. In 2005, ASMFC amended its FMP and approved Addendum II, placing a “cap” of 233 million pounds on Virginia’s industrial menhaden fishery. At the same time, the Addendum initiated a research program that will cost tax payers between one and two million dollars to determine the status of menhaden in the Bay and assess whether localized depletion is occurring. The token response of a Bay “cap” was far less than what the environmental community, the public and most of the fisherman had requested. ASMFC also ignored the scientific community that had published reports and peer reviewed papers explaining how insufficient numbers of menhaden are unable to support the nutritional needs of the Bay’s older striped bass. By the summer of 2006 Virginia had still failed to pass legislation to adopt Addendum II. Then instead of taking action against Virginia for being out of compliance, the ASMFC accepted a proposal from Virginia for a higher adjustable “cap” that allows an underage amount in one year to be added to the next years allowable harvest that could total 270 million pounds during a single year. Ignoring established protocol, ASMFC quickly drafted this change as Addendum III. Since menhaden industrial landings continue to decline in the Bay because of recruitment overfishing and increased striped bass predation, its unlikely either “cap” could save any fish because both “caps” are based on higher average landings from the previous five years. In the fall of 2006, after additional public comment, the ASMFC approved Addendum III with the higher “cap”. In 2007 the Chesapeake Bay industrial menhaden harvest will now be allowed to increase under Addendum III to 270 million pounds, about 65% more than was caught in 2006.

Numerous peer reviewed scientific studies have documented that the declining number of menhaden in the Chesapeake Bay is inadequate to support the growth and health of older striped bass. ASMFC’s decision to delay management action until further long term research is completed is illogical, clearly unjustified and damaging to the bay’s ecosystem. Fishermen should contact their elected officials and insist that ASMFC take action now to rebuild the menhaden stock through an ecological approach using existing science that considers the forage required for the maintenance of a healthy striped bass population in the Chesapeake Bay and along the Atlantic coast. The ecology of the entire Atlantic coast is affected by how the ASMFC manages Atlantic menhaden - the most important fish in the sea.


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