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Fishing to the Limits: The Trouble with Maximum Sustainable Yield and the Need for Target and Limit Reference Points

Fact Sheet


Stuart Gregory, Getty ImagesFor more than 80 years, the health of global fish stocks has been measured against the yardstick of “maximum sustainable yield,” or MSY. Looking only at individual species of fish being targeted, fisheries managers pursued the ideal of allowing fishing at the highest possible rate that a population could be expected to withstand on average. The goal of fishing to the level of MSY (FMSY) was embraced by the world community and incorporated into several important international agreements, including the United Nations Convention on the Law of the Sea (UNCLOS).

Today, it is widely recognized that managing fisheries with the aim of maximizing catches is too risky, given natural environmental fluctuations, increased stresses on the marine environment, and the role of target fish species in their ecosystems (and the consequences of unmanaged removal). Limited information regarding catch levels, the impact of management measures, and the condition of the fish population adds to the uncertainty. Acknowledging these shortcomings, the international community agreed in 1995 to apply a precautionary approach to managing fish stocks on the high seas. The U.N. Fish Stocks Agreement (UNFSA) calls for precautionary standards—“target” and “limit” reference points—that are designed to account for uncertainty and to keep fishing within sustainable limits.

This briefing paper explores the limitations of management regimes based solely on single-species MSY and explains the need for new regimes for high seas fisheries based on precautionary target and limit reference points.

Introduction to MSY

Target and Limit Reference Points: A Precautionary Approach to Fisheries Management

In 1977, P.A. Larkin published his seminal article, “An Epitaph for the Concept of Maximum Sustainable Yield,” signaling the growing awareness within the scientific community of MSY’s many flaws and limitations. Even as the goal of achieving and maintaining MSY was being incorporated into international agreements such as UNCLOS and the treaties establishing many of the world’s regional fisheries management organizations (RFMOs), scientists were questioning the sustainability of management regimes based solely on MSY.

A holistic and precautionary approach to fisheries management was called for more than 35 years ago—one that accounted for both the uncertainty inherent to fisheries and the complex interactions between commercial fish stocks and the wider marine ecosystem. This concept of precautionary management for our planet’s natural capital came into the international spotlight at the 1992 Earth Summit in Rio de Janeiro. The 154 countries present agreed that responsible resource management required the application of the precautionary principle, meaning that management should be more cautious when information is uncertain, unreliable, or inadequate, as is often the case in fisheries. This concept was subsequently enshrined in the Rio Declaration as well as the 1995 UNFSA.

Introduction to Target and Limit Reference PointsIn fisheries, the precautionary approach entails developing management policies and strategies that account for the inherent risks and uncertainties. Fundamental to this approach is the idea of using two reference points for fisheries management: a limit reference point intended to constrain catch within safe biological limits, and a target reference point intended to meet management objectives, such as desired biological, social, and economic outcomes.

Annex II of the UNFSA provides guidance on the precautionary management of highly migratory and straddling fish stocks (see Appendix 1). It explains that management strategies should be designed so that target reference points are “not exceeded on average” and “the risk of exceeding limit reference points is very low.” Typically, this type of management builds in responsive measures—such as fishing effort reductions or temporary closures to the fishery—that are triggered when reference points are surpassed. The use of target and limit reference points essentially creates a buffer to protect against the possibility of overfishing, allowing fisheries managers to respond to unexpected changes in a stock’s status before the health of the resource is seriously threatened.

Setting Precautionary Reference Points: MSY As the Limit

Traditional fisheries management regimes essentially treated FMSY as a target. Limit reference points, if used at all, were set above this level at a point where catches were already exceeding levels that were sustainable in the long term. A precautionary approach, on the other hand, treats MSY as the outer limit of what is acceptable in managing a particular stock. As stated in UNFSA:

Limit reference points set boundaries which are intended to constrain harvest within safe biological limits within which the stocks can produce maximum sustainable yield. ... The fishing mortality rate which generates maximum sustainable yield should be regarded as a minimum standard for limit reference points.

BluefinIn other words, although fisheries managers may choose to set even more precautionary limits, they must at least constrain catches within MSY. Management targets should be set even more conservatively to account for uncertainty in the fishery and to promote management objectives other than catch, such as preserving the stock’s role in the broader ecosystem or maximizing the economic value of the catch. As a limit or ceiling, FMSY is a useful management tool and should not be abandoned. To bring high seas fisheries management in line with best practices, MSY-based limits should be coupled with precautionary management targets that seek to return biomass levels to sustainable levels where stocks have fallen to MSY or below, or to prevent such a situation from occurring. 

Limited Progress

Despite the clear mandate in UNFSA and the agreement reached by Heads of State in Rio, the precautionary principle has yet to be implemented beyond a few notable examples. Consequently, most of the world’s fisheries are in danger
of overexploitation. Several RFMOs operate under outdated mandates established before the adoption of the UNFSA and continue to manage the fish species under their remit with the goal of achieving MSY. Even among the few RFMOs that have committed to using target and limit reference points, implementation has been incomplete.

Only two of the five major tuna RFMOs—the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC)—have committed to applying target and limit reference points, but neither has implemented them to date. The Antigua Convention, which entered into force in 2010, replaced and strengthened the IATTC’s original mandate by requiring the Commission to apply the precautionary approach in accordance with the UNFSA and the Food and Agriculture Organization of the United Nations (FAO) Code of Conduct for Responsible Fisheries.

The WCPFC Convention endorses the UNFSA approach to target and limit reference points even more strongly. It makes Annex II of UNFSA “an integral part” of the Convention and requires the Commission to “determine, on the basis of the best scientific information available, stock-specific reference points and the action to be taken if they are exceeded.”

Despite these commitments, IATTC has not established target and limit reference points for any of the species it manages. Meanwhile, the WCPFC has been making slow progress, but target and limit reference points have not been adopted for any fishery in the convention area.

Positive examples do exist, however:

  •  The Northwest Atlantic Fisheries Organization (NAFO) has developed a Precautionary Approach Framework that prescribes the use of "buffer" and limit reference points. In accordance with the UNFSA, the framework states that limit reference points for fishing mortality (Flim) cannot exceed the mortality level expected to produce MSY (FMSY). NAFO had adopted reference points for the capelin fishery and is in the process of developing them for shrimp. 
  •  The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has adopted precautionary target and limit reference points for krill fisheries as part of a suite of progressive, ecosystem-based management tools. 


Fishing boatScientists today have a much better understanding of the ocean ecosystem than they did 80 years ago, when the concept of MSY was introduced. Experts widely recognize that managing fish populations to MSY is risky for both fishermen and ecosystems. In order to maintain sustainable fisheries and healthy and resilient ocean habitats, fisheries management must account for limited information, unpredictable environmental fluctuations, and increased stresses on the marine environment.

The international community has agreed on a way forward. States and RFMOs must act to implement the precautionary principle by establishing target and limit reference points for the fisheries they manage. Although some progress has been made, there is still a long way to go.

To view the complete briefing, including citations and references, download the file from the link below.

Fact Sheet File: Fishing to the Limits: The Trouble with Maximum Sustainable Yield and the Need for Target and Limit Reference Points (PDF)


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