Atlantic menhaden is an important fish species because it forms a critical link between the upper and lower levels of the Bay food web. While menhaden populations along the Atlantic coast appear to be healthy, there is concern about low regional abundance (also referred to as “localized depletion”), specifically in Chesapeake Bay. To prevent a possible future decline of this keystone species, a cap has been placed on the amount of menhaden that can be harvested from the Bay. In addition, scientists are currently studying the effects of predation and fishing on menhaden as part of a multi-species model of the coast-wide Atlantic menhaden stock.
Atlantic menhaden is a keystone species that forms a critical link between the lower and upper levels of the Bay food web. In addition, menhaden make up one of the oldest and largest commercial fisheries on the Atlantic coast.
Atlantic menhaden are a significant link in the Bay food web. Like oysters, menhaden are filter feeders, grazing on algae and other planktonic organisms. This action helps cleanse the water of excess nutrients that contribute to the Bay's poor water quality.
In turn, the Bay's menhaden population is a key food supply for many commercially and recreationally valuable predatory fish, including bluefish, weakfish and striped bass. Fish-eating birds, such as ospreys and bald eagles, also rely on menhaden as a source of food.
The Bay's commercial Atlantic menhaden fishery is one of the most important and productive on the Atlantic coast. More pounds of menhaden are landed each year than any other fish in the Bay.
While this small, oily fish is not edible by humans, menhaden are used for a variety of other purposes, including:
Atlantic menhaden are typically caught using purse seines, then processed into oil or fish meal (called reduction). The Bay's major fishery and reduction industry for menhaden is located in the Virginia portion of the Chesapeake. Menhaden are also caught with pound nets in a bait fishery in the Potomac River and the Maryland portion of the Bay.
More pounds of menhaden are landed each year than any other fish in the Bay. Menhaden—along with blue crabs—have dominated the Bay's commercial fisheries during the past 60 years. In 2006, 376 million pounds of menhaden were caught in Maryland and Virginia waters (both Chesapeake Bay and Atlantic Ocean), valued at approximately $22.8 million.
Chesapeake-specific population estimates for menhaden are not currently produced; estimates are only made for the entire Atlantic coast stock, which appears to be healthy. Still, scientists are concerned about what appears to be a low abundance of menhaden in the Bay, which is one of the fish's key nursery areas.
Fisheries-independent data from seine surveys in Maryland and Virginia through 2004 suggested that menhaden recruitment—the number of juveniles that grow to a “catchable” size—was possibly declining in the Bay. Coast-wide recruitment is considered to be at median historic levels.
The exact causes of the decline in recruitment remain unknown. While additional scientific knowledge is necessary to understand the variability of menhaden recruitment, scientists have cited several possible contributing factors, including:
The historical ecological functions of Atlantic menhaden may be diminished if populations decline in the Bay. Low menhaden abundance may create a reduced food supply for striped bass, bluefish, weakfish and other commercially and recreationally valuable predator species. Recent studies suggest that the Bay's striped bass are suffering from poor nutrition, which may be leading to slower growth rates and higher susceptibility to mycobacteriosis.
The Atlantic menhaden fishery is managed by the Atlantic States Marine Fisheries Commission (ASMFC), which tracks and regulates how many menhaden are—and can be—caught each year, as defined in the ASMFC's Interstate Fishery Management Plan for Atlantic Menhaden.
In October 2006, the ASMFC approved Addendum III to Amendment 1 of the Interstate Fishery Management Plan for Atlantic Menhaden. Addendum III established a five-year annual cap of 109,020 metric tons—or approximately 240.3 million pounds—on menhaden reduction fishery harvests in the Bay. This harvest limit was based on the average landings from 2001-2005. The cap was implemented in 2006 and will extend through 2010.
In addition to the cap, a research program is being conducted to:
The controversial decision is meant to protect the critical species from continued overfishing.
Researchers in Maryland measure juvenile menhaden abundance by casting nets and recording the percentage of hauls with menhaden present. These are called “positive hauls.” The 2010 data show that menhaden were caught in 25 percent of the hauls
Publication date: December 01, 2002 | Type of document: Report | Download: Electronic Version
Available in digital format and hardcopy. Phytoplankton standing stocks, production, and species composition are potentially influenced by both the supply of nutrients to the bottom of the food web and removal by suspension feeders higher…