Atlantic menhaden caught as part of Maryland's Estuarine Fish Community Sampling Program. Photo © Frank Marenghi, MD DNR.
Atlantic menhaden (Brevoortia tyrannus) occupy estuaries and coastal waters from northern Florida to Nova Scotia and are believed to consist of a single population. Adult and juvenile menhaden form large, near-surface schools, primarily in estuaries and nearshore ocean waters from early spring through early winter. By summer, menhaden schools stratify by size and age along the coast, with older and larger menhaden found farther north. During fall-early winter, menhaden of all sizes and ages migrate south around the North Carolina capes to spawn.
Sexual maturity begins as early as age one to just before age three, with major spawning areas from the Carolinas to New Jersey. The majority of spawning primarily occurs offshore (20-30 miles) during winter. Buoyant eggs hatch at sea, and larvae are carried into estuarine nursery areas by ocean currents. Juveniles spend most of their first year in estuaries, migrating to the ocean in late fall.
Menhaden are very efficient filter feeders. Water is pushed through specialized gill rakers that are formed into a basket that allows them to capture plankton. Menhaden are an important component of the food chain, providing a link between primary production and higher organisms by consuming plankton and providing forage for species such as striped bass, bluefish, and weakfish, to name just a few.
The Atlantic menhaden commercial fishery consists of a reduction fishery (named because it "reduces" the whole fish into fish meal, fish oil, and fish solubles) and a bait fishery. The reduction fishery first began in New England during the early 1800s and spread south after the Civil War. The reduction fishery grew with the advent of purse seines in the mid-1800s and reached peak landings in 1956 at 712,100 metric tons (mt). At the time, over 20 menhaden reduction factories ranged from northern Florida to southern Maine. In the 1960s, the Atlantic menhaden stock contracted geographically, and many of the reduction factories north of the Chesapeake Bay closed due to a scarcity of fish. Consequently, reduction landings dropped to 161,000 mt in 1969. In the 1970s and 1980s, the menhaden population began to expand (primarily due to a series of above average year classes entering the fishery), and reduction landings rose to around 300,000-400,000 mt. Adult menhaden were again abundant in the northern half of their range and, as a result, reduction factories in New England and Canada began processing menhaden again by the mid-1970s. However, by 1989 all shore-side reduction plants in New England had closed, mainly because of odor abatement regulations.
During the 1990s, the Atlantic menhaden stock contracted again, largely due to a series of poor to average year classes. Over the next decade, several reduction plants consolidated or closed, resulting in a significant reduction in fleet size and fishing capacity. By 2006, there was only one remaining reduction plant in operation on the Atlantic coast processing menhaden into fishmeal and oil. This is the Omega Protein plant, located in Reedville, Virginia, which is still operational today. In 2018, roughly 141.3 thousand mt were landed for reduction purposes.
Commercial landings in 2018, including directed (reduction and bait), incidental catch, and episodic event landings, were 191,202 mt, approximately an 11% increase in landings from 2017.
In February 2020, the Board accepted the results of the Single-Species and Ecological Reference Point (ERP) Assessments and Peer Review Reports for management use. The single-species assessment acts as a traditional stock assessment using the Beaufort Assessment Model (BAM), and indicates the stock is not overfished or experiencing overfishing relative to the current single-species reference points. The ERP assessment evaluates the health of the stock in an ecosystem context, and indicates that the fishing mortality (F) reference points for menhaden should be lower to account for menhaden’s role as a forage fish.
According to the BAM model, population fecundity (i.e., number of mature eggs in the population), has been above the single-species threshold since 1991 and above the single-species target in 20 of the 27 years since then, including 2017. F has remained below the single-species overfishing threshold (0.6) since the mid-1970s, and below the single-species overfishing target (0.22) since the mid-1990s. F was estimated to be 0.11 in 2017. The model also found that juvenile abundance was low in 2017, while biomass was relatively high.
The ERP assessment uses the Northwest Atlantic Coastal Shelf Model of Intermediate Complexity for Ecosystems (NWACS-MICE) to develop Atlantic menhaden ERPs. NWACS-MICE is an ecosystem model that focuses on four key predator species (striped bass, bluefish, weakfish, and spiny dogfish) and three key prey species (Atlantic menhaden, Atlantic herring, and bay anchovy). These species were chosen because diet data indicate they are top predators of Atlantic menhaden or are key alternate prey species for those predators. A more detailed overview of the stock assessments is available here.
An important conclusion from the ERP assessment is that the final ERP definitions and values, including the appropriate harvest level for menhaden, depend on the management objectives for the ecosystem (i.e., management objectives for both Atlantic menhaden and its predators). Accordingly, the ERPs assessment did not recommend a specific ERP F target or threshold. Instead, the ERP assessment recommends a combination of the BAM and the NWACS-MICE models as a tool for managers to evaluate trade-offs between menhaden harvest and predator biomass.
In order to explore the utility of this new management tool, the Board tasked the ERP Workgroup to explore how different F assumptions for the other predator and prey species in the NWACS-MICE model (i.e., bluefish, weakfish, spiny dogfish, and Atlantic herring) might affect the ERP F target and threshold for menhaden. The Board will review these analyses and take up the issue of formally adopting ERP in May 2020.
Atlantic menhaden are currently managed under Amendment 3 to the Interstate Fishery Management Plan (FMP). The amendment maintains the management program’s single-species biological reference points until the adoption of menhaden-specific ERPs. Amendment 3 also changes commercial quota allocations to strike an improved balance between gear types and jurisdictions, and to facilitate future growth in the fisheries. The amendment allocates a baseline quota of 0.5% to each jurisdiction, and then allocates the rest of the annual TAC based on historic landings between 2009 and 2011. This measure provides fishing opportunities to states which previously had little quota while still recognizing historic landings in the fishery. The Amendment also prohibits the rollover of unused quota, maintains the 6,000 pounds trip limit for applicable gear types following the closure of a directed fishery, and sets aside 1% of the TAC for episodic events in the states of New York through Maine. Lastly, the Amendment reduces the Chesapeake Bay cap, which was first implemented in 2006 to limit the amount of reduction harvest within the Bay, to 51,000 mt. This recognizes the importance of the Chesapeake Bay as nursery grounds for many species by capping reduction landings from the Bay to current harvest levels.
In November 2017, while taking final action on Amendment 3, the Board established a 216,000 mt TAC for the 2018 and 2019 fishing seasons. In August 2019, the Board maintained the 216,000 mt TAC for 2020 with the option to revisit the 2020 TAC following review of the single-species and ERP assessment reports. Fortunately, the ERP assessment indicated that the conservative TAC the Board has set since 2017 is consistent with the ERP F target example provided in the ERP assessment.