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 Ecological 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.