Tuna Stocks – Looking after the fish supply

The countries of the WCPO work together to maintain healthy populations of tuna and other fish. Their management decisions are based on the latest science on fish numbers and changes in populations.

Policy and Rules

Policies and rules govern how tuna stocks are maintained

The Western and Central Pacific Fisheries Commission (WCPFC) meets once a year to decide on rules and policies that support the management of the tuna fisheries of the Western and Central Pacific Ocean (WCPO). The rules are called conservation and management measures (CMMs). They are binding. The WCPFC also sets resolutions, which are recommended courses of action but not binding.

The WCPFC is made up of three groups of countries: members, cooperating non-members, and participating territories. They are known collectively as CCMs. Among the members are the 14 small island developing states (SIDS) of the WCPO.

WCPFC maintains all CMMs and resolutions.

Extra rules apply in waters governed by the Parties to the Nauru Agreement (see below).


CMMs for managing tuna populations

The CMMs that affect how populations of tuna and other species are managed are summarised on this page. Links to the complete CMM are provided.



2020-01, Bigeye, yellowfin and skipjack tuna in the Western and Central Pacific Ocean Purse seine fishery in tropics (20°N20°S)

  • Prohibits setting of fish-aggregating devices (FADs) JulySeptember in exclusive economic zones (EEZs) and high seas
  • Additionally prohibits setting of FADs for 2 months in a row, either AprilMay or NovemberDecember (except for Kiribati-flagged vessels in adjacent high seas)
  • From 1 January 2020, all existing and new FADs must be constructed to prevent the entanglement of sharks, turtles, and other bycatch. Mesh should be avoided, but if it is used should be wrapped tightly around the raft so that it doesnt hang loose. Tails should be weighted, and if made of mesh, bundled tightly into a sausage shape. Mesh size to be no larger than 7 cm when stretched.
  • The use of biodegradable materials is recommended
  • No vessel is have more than 350 FADs with activated instrumented buoys
  • Effort and catch within EEZs needs to match existing limits
  • Non-SIDS need to restrict their purse-seine fishing efforts on the high seas to stated limits
  • When a country exceeds effort and catch limits, the excess amount will be deducted from the limits for the following year
  • All vessels are to retain on board and then land or ship at port all their catch
  • All purse-seine vessels shall carry an official observer
  • Except for SIDS and Indonesia, no country is to increase the number of its vessels that are larger than 24 metres and have freezer capacity

Read the CMM


2020-01, Bigeye, yellowfin and skipjack tuna in the Western & Central Pacific Ocean

Longline fishery

  • Catch limits are set for bigeye tuna for all countries catching 2,000 tonnes or more per year
  • Countries that caught less than 2,000 tonnes in 2004 are not to increase their catch above 2,000 tonnes a year
  • Longline vessels are not to increase their catches of yellowfin tuna
  • Peoples Republic of China, Indonesia, Japan, Republic of Korea, Chinese Taipei and USA are to report monthly on bigeye catches
  • Except for SIDS and Indonesia, no country is to increase the number of its longline vessels targeting bigeye tuna that have a freezing capacity or ice-chilling facilities

Read the CMM


2020-01, Bigeye, yellowfin and skipjack tuna in the Western & Central Pacific Ocean 

Other commercial fisheries

  • Total effort and capacity of other commercial bigeye, yellowfin and skipjack tuna fisheries (taking more than 2,000 tonnes) is not to exceed the average level of 200104 or 2004

Read the CMM


2020-01, Bigeye, yellowfin and skipjack tuna in the WCPO

Target reference points

  • Pending agreement, spawning biomass for bigeye and yellowfin tuna to be maintained at or above the average set for 201215
  • Pending agreement, spawning biomass for skipjack tuna to be maintained at 50% of the level that occurs in the absence of fishing (see CMM 2015-06)

Read the CMM


2019-02, Pacific bluefin tuna

  • For vessels operating north of 20°N, total fishing effort should stay below the 200204 annual average levels, and catches of individual fish smaller than 30 kg should be reduced to 50% of the 200204 annual average
  • When more than the limit is caught, the excess will be deducted from the catch limit in the following year
  • If less than the limit is caught in any year, a maximum of an extra 5% of the annual limit may be carried over to the following year
  • For 201820, part of the annual catch limit for tuna smaller than 30 kg can be used to catch tuna larger than 30 kg in the same year. Fish larger than 30 kg cannot be used to catch fish smaller than 30 kg.
  • Annual reports about these tuna catches are required by 31 July
  • CCMs to monitor numbers of juveniles each year, to contribute to knowledge about numbers of surviving offspring
  • Strengthen monitoring and data collection for fisheries and farming to improve data quality and reporting

Read the CMM


2019-03, North Pacific albacore

  • Fishing for albacore tuna north of the equator is not to be increased above 2005 levels, and work is needed to maintain or to reduce fishing efforts
  • All CMMs are to report annually to WCPFC on catch by weight, and fishing effort by gear used

Read the CMM


2015-02, South Pacific albacore

  • Fishing for albacore tuna south of 20°S is not to be increased above 2005 levels, and work is needed to only maintain or to reduce fishing efforts
  • SIDS have a legitimate right to responsibly develop their own albacore fisheries in the waters under their jurisdiction
  • Each fishing vessel operating south of 20°S needs to report annually to the WCPFC about the total catch

Read the CMM


2015-06, Target reference point for skipjack tuna

  • The interim target reference point for skipjack is to be 50% of the estimated recent average spawning biomass in the absence of fishing
  • The target reference point will be estimated using the same methods that are used for the limit reference point for skipjack
  • The Scientific Committee will refer to this reference point when assessing the status of skipjack stocks and when recommending any changes due to possible local reductions or geographical shift in stocks

Read the CMM


Other species

2010-01, North Pacific striped marlin

  • Total catch is to be 80% of the highest catch between 2000 and 2003
  • Each flag/chartered fishing vessel operating north of the equator must report annually on its actions to reduce its catch, and on the total catch taken

Read the CMM


2009-03, Swordfish

  • Each participating country has an agreed maximum number of fishing vessels that may operate south of 20°S, and will not shift its fishing efforts north of this area
  • SIDS have a legitimate right to responsibly develop their own swordfish fisheries in the Convention area
  • All participating countries will cooperate on research aimed at reducing uncertainty about the status of swordfish stocks
  • Annual reports need to be made to the WCPFC on the total catch and the total number of all vessels fishing south of 20°S

Read the CMM


2006-04, Striped marlin in the south-west Pacific

  • Each participating country has an agreed maximum number of fishing vessels that may operate south of 15°S
  • SIDS have a legitimate right to responsibly develop their own striped marlin fishery south of 15°S
  • All fisheries will report annually to the WCPFC on the striped-marlin catch, whether if is from direct fishing or as bycatch

Read the CMM

Setting the rules delegates in session at the 16th annual meeting of WCPFC, in Port Moresby in December 2019. Photo: F. Tauafiafi.


Extra rules apply in PNA waters

Any vessel fishing in the exclusive economic zone (EEZ) of PNA member states must be licensed to do so, and also abide by any other PNA rules as well as the CMMs of the WCPFC.

The members of the PNA seek to ensure their rules are consistent among members and with WCPFC rules. Article 1 of the agreement (signed in 1982 and amended in 2010) says:

The Parties shall seek, without any derogation of their respective sovereign rights, to coordinate and harmonise the management of fisheries with regard to common stocks within the Fisheries Zones, for the benefit of their peoples.

Under the authority of the PNA, the member states have implemented two schemes that allow them to require fishing vessels to have a licence to fish in EEZ waters. The two agreements are the Palau Arrangement for the operation of the Purse Seine Vessel Day Scheme (amended October 2016) and a similar arrangement for the Longline Vessel Day Scheme (amended October 2016).

The arrangements set out the operating rules for these two types of fishing vessels. Under the rules, the PNA members sell a limited number of fishing days in the exclusive economic zones of the PNA states.

They also detail how the PNA manages tuna stocks (populations) sustainably while maximizing local incomes.


Tuna stocks are managed to keep numbers healthy

Three organisations share responsibility for how tuna populations are managed for the region as a whole. The sub-regional group of countries that are members of the Parties to the Nauru Agreement also have rules that govern the management of tuna stocks in their waters.

A baiter at work throwing into the water effective management of tuna stocks is vital for the economic development of SIDS and to keep tuna numbers at healthy levels. Photo: Francisco Blaha.


FFA helps small island nations manage

The Pacific Islands Forum Fisheries Agency (FFA) takes an ecosystem approach to managing fisheries. The agency helps its members to apply this approach to managing tuna fisheries under their power. This is important support for the 14 small island developing states (SIDS) of the Western and Central Pacific Ocean.

An ecosystem approach puts management into the context of the whole food web and peoples cultural, social and economic needs. Fisheries managers consider the health and abundance of tuna and other desired fish. They may consider factors that affect these. For example, a declining ecosystem, ad hoc management policies, and greater demand for tuna can make it harder for tuna to thrive.


WCPFC sets management rules for the region

Management of the tuna fisheries is also central to the work of the Western and Central Pacific Fisheries Commission (WCPFC). Its work covers the exclusive economic zones (EEZs) of countries in the region, as well as the high seas of the region.WCPFC is the central decision-making body for managing tuna fishing in the Western and Central Pacific Ocean (WCPO). It was established in mid-2004 by the Convention for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean.


  • uses scientific advice to assess current stocks of tuna and other commercial fisheries
  • sets binding rules, called conservation and management measures (CMMs), to help maintain sustainable populations of all commercial fish species
  • receives reports on the catch and harvest of species from members, participating territories and cooperative non-members
  • revises and updates CMMs based on reports and new scientific information.

The convention requires the WCPFC to consider the whole ecosystem when it sets rules. The commission needs to take into account the impact of fishing on:

  • target stocks, that is tuna and other fish that fishing nations seek to catch
  • non-target species, that is juvenile tuna that are too young to reproduce, and other fish and sea animals
  • species that are often found with or depend on tuna and other target stocks
  • other species that live in the same environment as the target stocks
  • the variety of species (biodiversity) in the ocean, and their dependence on each other to thrive.


SPC monitors fish numbers and health

The Pacific Community (SPC) helps to manage the Pacifics tuna and other species by monitoring and assessing fish stocks. It does this through its Oceanic Fisheries Programme.SPC manages the worlds largest international fisheries database. Participating countries provide standardised data on fishing operations. The first records were received in 1950, and the database now holds about 2.7 million records. They have come from more than 9,000 different vessels.


PNA has extra rules that cover the worlds largest purse-seine tuna fishery

The Parties to the Nauru Agreement (PNA) covers the worlds largest sustainable fishery of tuna caught by purse-seine vessels. Eight countries have signed the agreement. Between them, they provide about 50% of the global supply of skipjack tuna, the most commonly canned tuna.

The PNA has two main practices for conserving its fish stocks:

PNA has several agreements that help members manage tuna stocks in their waters.

Palau Arrangement for the operation of the Purse Seine Vessel Day Scheme sets the rules for fishing in the EEZs of the PNA states. All purse-seine vessels wanting to fish in the EEZs must be licensed under the scheme. A Longline Vessel Day Scheme operates in the same way.

The PNA members meet every year to set limits on the total amount of fishing allowed. This is calculated a a total allowable effort (TAE) allowed by all vessels in a year. This is the number of fishing days allowed. The TAE is usually set a couple of years ahead. The parties review the measures designed to maintain and conserve fish stocks. They look at the current status of fish stocks. They also consider other factors that help fish maintain healthy numbers, for example the measure to reduce fish deaths, especially of young bigeye and yellowfin tuna.

They also take into account other scientific, economic and management information.

Best Practices

Management best practice for fish-aggregating devices


The FFA helps the small island developing states (SIDS) to develop plans for managing fish-aggregating devices (FADs). The devices affect how fish behave and how many fish are caught. FADs take advantage of the natural habit of some fish, including tuna, to group around objects floating in the water.

A Solomon Islands subsistence fisher at work. Photo credit: Francisco Blaha.

FADs are used to attract fish that naturally gather in dense schools. This means that less time is spent searching for them. The practice is particularly useful when fishing for highly migratory fish such as tuna. But FADs can:

  • reduce populations of bigeye and yellowfin tuna when purse-seine fishers catch juvenile fish that group around FADs
  • interfere with longline fishing, because they increase the risk fishing gear becoming entangled in the mooring ropes of FADs.


What are FADs?
Fish-aggregating devices are structures that float on or near the surface of the water where fish may congregate.
Most are made by humans. They may be free-floating or anchored to the seabed. Examples are buoys, floats, netting, webbing, plastics, bamboo and log. Fish sometimes also gather around whale sharks.
In 2012, the Pew Environment Group estimated that the number of drifting FADs put into the oceans each year ranges from 47,000 to 105,000.

FAD management plans:

  • limit the number of FADs used by purse-seining fishing vessels
  • modifying the design, operation, location and maintenance of FADs to minimise disruption to other fisheries.

Since 1 January 2020, it has been compulsory for all FADs (existing and new) to be designed and constructed so that they cannot entangle sharks, turtles, and other animals that are not the target of fishing operations. The WCPFC also recommends that they be made of biodegradable materials.


Marine Stewardship Council certification

An evaluation of the sustainability of global tuna stocks relative to the Marine Stewardship Council criteria (March 2020) provides a basis for comparing stock scores. It is a useful source document for future tuna certifications or when establishing tuna fishery improvement projects (FIPs) and offers a snapshot” of the current status of the stocks.


PNA best practices

The PNA has two main practices for conserving its fish stocks:

  • limiting the catch of all fishing vessels through the Vessel Day Scheme, which is explained in more detail under Catch & harvest
  • banning the use of fish-aggregating devices by purse-seine fishers for three months a year.
Research and Training

Tuna numbers sustained using research and training

The Oceanic Fisheries Programme of the Pacific Community (SPC) monitors and assesses the populations (called stocks) of Pacific tuna and other fisheries.

Tagging tuna at sea

Tagging tuna at sea

It provides scientific advice to the WCPFC. It also provides data, scientific analysis and advice to PNA members. This information helps them assess tuna stocks and develop measures to manage fisheries.

Graham Pilling explains SPCs role in conducting stock assessments on the four major tuna species in the Western and Central Pacific, and how that feeds into decisions made by the WCPFC (1.39 mins).


Hear SPCs Andrew Hunt, who collects data for the Oceanic Fisheries Management Project (OFMP2), explain how that data feeds into stock assessment (32 secs).


Current status of tuna stocks

FFA describes the status of tuna stocks annually in a report card, and publishes the report cards and related documents on its website.

The Tuna Fishery Report Card 2020 contains the most recent assessment of the status of major tuna species. The abundance of a species is estimated against a benchmark called a target reference point (TRP), which is a desirable level of stock to maintain the healthy functioning of the environment and the sustainability of fishing. An interim TRP exists for albacore tuna. TRPs for the other three species are being developed.

All four species are assessed as being in biologically healthy numbers. The current report card is summarised here:

  • Bigeye tuna is not overfished, and overfishing is not occurring, although there is a 1 in 8 chance of bigeye being overfished. The biomass of this tuna continues to decline, pointing to the need to strengthen management measures.
  • Skipjack tuna is not overfished, and overfishing is not occurring. The stock is above the TRP. Improved understanding of skipjack biology has been incorporated into modelling of stock health.
  • South Pacific albacore tuna is not overfished, and overfishing is not occurring. However, as it is estimated to be below the interim TRP, the catch must be reduced. This will help improve catch rates so they are economically viable.
  • Yellowfin tuna is not overfished, and overfishing is not occurring.

For more details see:

The SPC’s Dr John Hampton explains the change in the way bigeye is assessed, and what it means (3.29 mins).


Models are used to help assess tuna stocks

Estimating tuna populations in the Western and Central Pacific Ocean is a challenge. Tuna are always on the move, driven by ocean currents, changes in the availability of their prey, and other processes that vary naturally. There are many gaps in knowledge about their biology and lifecycle, which further complicates assessments.

Tuna are caught by fishing fleets that record and report their catches with varying degrees of accuracy. Sampling is limited to a tiny fraction of this commercial catch, and is often not representative of the tuna population at large.

Not only must the numbers and weight of each species be estimated, but these values have to be compared with the population size that would produce the maximum yield in the future. SPCs tool over the past decade is a computer model called MULTIFAN-CL. It integrates information from three main sources.

The first is length or frequency data, which is gained by counting and measuring a sample of the fish caught by commercial vessels. From this, it is possible to estimate the relative numbers of fish of different ages in different areas of the Pacific, and to understand recruitment (additions to the population) and mortality (losses from the population) among tuna.

The second is the relationship between the fishing effort (the number of days spent fishing) and the catch, captured using log sheets that commercial vessels are required to complete. As the number of fish in the sea is reduced, they become more sparsely distributed and an average fishing trip will have smaller catches. Understanding this relationship helps researchers track changes in the size of the fish population.

The third source of information comes from tagging programs, in which tuna are caught, marked with small numbered tags, and released. When tagged fish are re-caught and reported, estimations can be made of fish populations.

The results of this modelling are provided to the WCPFC.

SPC also assesses tuna stocks using another model, SEAPODYM (Spatial Ecosystem and Population Dynamics Model). It uses data on climate, other environmental factors, and fish populations, among other factors. This model is important for understanding the potential impacts of climate change.

The SPCs Oceanic Fisheries Programme Manager, Dr John Hampton, explains the use and benefits of the two stock-assessment models, and their basic differences (2.46 mins).


Tuna tagging contributes to assessments

Tuna tagging is also used to collect information that is used in stock assessments. SPC conducts a region-wide tuna-tagging project. The data collected are fed into SEAPODYM modelling.

Tagging helps scientists get information about the growth, movements, natural mortality and fishing mortality of the tuna, which helps estimate the status of the stocks and the impacts of fishing.

SPC has a dedicated tuna-tagging portal that contains information about all the tagging programs, including details of what to do if you catch or find a tagged tuna.


Research improvements flagged

The following have been identified as critical to research to improve our knowledge of tuna stocks in the WCPO:

  • Improve estimates of tuna growth, including regional differences.
  • Continue tagging and analysis to support future assessments.
  • Assess otoliths (inner-ear structure in fish) to work out fish age and growth.
  • Continue to analyse pole-and-line catch rates, longline efficiency, longline models, and purse-seine indices.
  • Improve estimates of natural tuna mortality and use parts of longline-caught fish to do so.
  • Consider biological markers to improve estimates of eastwest movement.
  • Refine modelling approaches for maturity and sex of tuna.


Training on how to assess tuna stocks

The Oceanic Fisheries Management Project works with SPC to deliver annual stock-assessment training workshops. The workshops, which have been run since 2006, help fisheries professionals know how to interpret the very complex stock assessment data. This contributes to ensuring that regional decisions about tuna stocks are made in an informed way, and are based on the best available science.

Officers learn how to:

  • understand and interpret the results from the regional oceanic fisheries stock assessments
  • communicate this information to fishery managers within their countries
  • increase their confidence to participate in scientific discussions of the WCPFC in particular, during meetings of its Scientific Committee.

The courses have attracted people from 28 countries. By the end of 2020, 141 people had attended an average of 2 courses each: 41% (58) being women, and 59% (117) men. In May 2021, the first online workshop will be run.

Participants in the 2019 Advanced Stock Assessment Workshop run by SPC collaborate on an exercise on using a Majuro plot, a graphic that illustrates tuna stock status. Photo: SPC.


Resources on tuna stocks

You can find news stories, popular articles, opinion pieces and blog posts on tuna stocks on the Tuna stocks news and views page.

Pole-and-line fishing, as here, is one of several ways used to catch tuna in the WCPO. Photo: Francisco Blaha.

Pole-and-line fishing, as here, is one of several ways used to catch tuna in the WCPO. Photo: Francisco Blaha.


Fact sheets


Technical papers


Technical papers on FADs


Posters and videos

In Taking stock of our tuna, SPC talks about the importance of the tuna fisheries to the economic development of the Pacific Islands (24.19 mins). The video is also on the Pacific Community website.


Inside out: saving our tuna, video (23.04 mins) about managing tuna populations in the WCPO, produced by United Nations Development Programme, 2014


Tuvalu’s Nikolasi Apinelu talks tuna at OFMP2 project forum, about matching reported and IUU fishing levels, and stock status, for Tuvalu (1.39 mins).


Samoa’s Magele Etuati Ropeti talks tuna at OFMP2 project forum, about assessing whether Samoa is creating a sustainable environment for using tuna (1.28 mins).


WWF’s Bubba Cook talks tuna at OFMP2 project forum, about overexploitation of tuna stocks (2 mins).


Pacifical is a company that was set up by the PNA countries to market tuna globally. In this video, Pacifical talks about its sustainable fishing policy and practice (4.55 mins).