July 2009 Update on EBFM for Chesapeake Bay

Update on Species and Quantitative Ecosystem Teams
The Socioeconomic Quantitative Ecosystem Team has held a series of meeting and conference calls over the past several weeks to finalize a human ecology map of EBFM for Chesapeake Bay and generate a new report entitled "A Review of Consumer Preferences for Eco-labeled Seafood: Potential Implications for EBFM Species in the Chesapeake Bay" (K. Appleman). These two pieces will be presented to fishery managers in the region in the coming month for their review and consideration and the eco-labeling report will be discussed in detail in our August EBFM Update. In addition the team continues to develop a plan for identifying and integrating stakeholders in EBFM in the Chesapeake Bay which will be implemented in October, 2009.

The Foodweb Quantitative Ecosystem Team will hold its next meeting on August 5 to review progress to date on the development of striped bass ecosystem-based reference points identified as short term goals at the April QET meeting. The Stock Assessment and Habitat Suitability QETs are in the process of planning meetings for early September to review their progress and prioritize team activities for the coming months.

The Alosine Species Team held its first conference call on July 1 and will be convening to identify the critical ecosystem concerns for Alosines in the Chesapeake Bay in early September in College Park, MD. The Blue Crab Species Team documents are under review by the team's Editorial Review Committee and will be finalized within the coming month. The Menhaden Species Team has completed its work and their background and ecosystem issue briefs are in the final stages of copy-editing at Maryland Sea Grant. These documents will be distributed to the QETs and fishery managers by August 7, 2009. Ed Houde, Chair of the Menhaden Species Team, provides his perspective on managing menhaden through an ecosystem-based approach in the following discussion.

Managing Atlantic Menhaden in Chesapeake Bay: An Ecosystem-Based Perspective
E. D. Houde, Ph.D., University of Maryland Center for Environmental Science
Chesapeake Biological Laboratory

The Atlantic menhaden Brevoortia tyrannus supports the Chesapeake Bay's largest fishery. In many years, the Bay fishery takes >100,000 tons of menhaden. Menhaden also is a key player in the Bay's food web – filtering plankton, cycling and recycling nutrients, and serving as prey for piscivores. Precautionary management that minimizes risk of collapse of the menhaden resource is critical to the wellbeing of the Bay, its fisheries and water quality. In many ways, menhaden epitomizes arguments in support of ecosystem-based fisheries management (EBFM). The importance of including menhaden in multi-species and EBFM plans for Chesapeake Bay has been recognized for more than a decade (CBP 2000; CBFEAP 2006) and Maryland Sea Grant is now leading an effort to develop an ecosystem-based plan.

Two issues are at the forefront of management and stakeholder concerns with respect to menhaden in Chesapeake Bay. These are "localized depletion" and persistent low recruitment (low abundances of young-of-the-year menhaden). Although the coastwide menhaden stock is judged to be neither overfished nor experiencing overfishing, some stakeholders and managers perceive a local problem, in which low abundance of menhaden compromises its role in providing two important ecosystem services: 1) forage for predators and 2) filtering and nutrient recycling that may benefit water quality. Traditional fishery management approaches do not formally consider such services in management plans. Ecosystem-based approaches should explicitly address these concerns.

Localized Depletion

It is clear that menhaden plays an important role as prey for piscivorous fishes and birds coastwide and in Chesapeake Bay. Protecting the forage role of menhaden for the benefit of piscivores (e.g., striped bass, bluefish, ospreys) by appropriate apportioning of menhaden mortality to the fishery and to its natural predators is a goal of EBFM. The goal should emphasize conservation of sufficient menhaden to feed a healthy predator community, avoiding "localized depletion" by optimizing allocation of a fraction of the menhaden stock to the historical fishery. In EBFM, this goal should focus on local, Chesapeake Bay needs. At present, "localized depletion" is only vaguely, and not quantitatively, defined. An EBFM should quantify it and recommend a management protocol to respond to it.

Filtering and Nutrient Recycling

The filtering service provided by menhaden and, especially, its importance to the Bay are poorly understood. There is no doubt that menhaden are filter feeders and feed on microscopic algae, but the significance of this service, in the context of Chesapeake Bay water quality, is not quantified. It will be a challenge to develop indicators and reference points for EBFM of menhaden, lacking firm knowledge or quantification of this ecosystem service. Nevertheless, in a precautionary sense, allocation of menhaden to the fishery could be regulated to insure that the menhaden resource is not depleted to a level where the service would be lost.

Low Recruitment

Menhaden has a complex life cycle that is dependent on connectivity between the coastal ocean and estuaries such as Chesapeake Bay (Figure 1), which adds to the complexity of developing EBFM. The low recruitment of menhaden in Chesapeake Bay for the past 20 years could result from climate and oceanographic variability acting on egg and larval stages in the coastal ocean, or it could result from environmental conditions acting on juveniles in the Bay. Chesapeake Bay historically has provided >65% of menhaden recruits to the coastwide population. In considering appropriate EBFM actions, the Quantitive Ecosystem Teams will deliberate on what, if any, precautionary management measures may be appropriate to recognize the present low abundances of young menhaden in Chesapeake Bay.

Figure 1. Life cycle of Atlantic menhaden. Adults spawn in the coastal ocean, where eggs and larvae are found. Late-stage larvae enter Chesapeake Bay and transform to juveniles, most of which leave the Bay in their first winter. Some adult menhaden also live in the Bay and support the fishery. Oldest and biggest menhaden primarily are found in the coastal ocean from the Mid-Atlantic to New England.

Present and Future Management

Atlantic menhaden is managed as a single, coastwide stock by the Atlantic States Marine Fisheries Commission (http://www.asmfc.org/). The ASMFC capped annual landings of the Chesapeake Bay purse-seine fishery at 109,020 tons for the period 2006-2010, largely in response to public concern about "localized depletion." This "local" and precautionary action essentially is an ecosystem-based measure to protect ecological services of menhaden in the Bay. The action was taken despite the conclusion by an expert, technical committee that the coastwide stock was not overfished.

The Maryland Sea Grant “Menhaden Species Team” has documented the issues surrounding menhaden management in Chesapeake Bay. The QETs will deliberate to identify and prescribe appropriate reference points, and possibly recommended specific management actions for EBFM of menhaden within Chesapeake Bay. A baywide plan with clear goals for conservation and utilization of menhaden will be a major step toward EBFM in Chesapeake Bay.

References

CBP. 2000. Chesapeake 2000. Chesapeake Bay Program. Annapolis, MD.

CBFEAP. 2006. Fisheries ecosystem planning for Chesapeake Bay. The Chesapeake Bay Fisheries Ecosystem Advisory Panel, with support of the NOAA Chesapeake Bay Office. American Fisheries Society, Trends in Fisheries Science and Management 3. Bethesda, MD.

Please contact Shannon Green, Fisheries Ecosystem Coordinator for Maryland Sea Grant, for further information. Thank you! sgreen@mdsg.umd.edu (301) 405-6372