Meryl J Williams

Meryl J Williams

Longtail tuna (Thunnus tonggol) is growing in importance on local and international tuna markets.

As a member of the genus Thunnus, longtail tuna is closely related to the main oceanic tunas such as the bluefin tunas, yellowfin, bigeye and albacore tuna. Yet, it has a very different habitat to these species. It lives in coastal and inshore areas, most commonly in depths less than 50 m. It is one of the neritic tunas (neritic: near shore).

AsiaPacific-FishWatch has compiled a profile of longtail tuna. This species is only found in the Indo-West-Pacific region, where catches match those of bigeye and albacore tuna. For landings, the top eight countries are Iran, Indonesia, Malaysia, Thailand, Oman, India, Pakistan and Yemen. Given these key countries, not surprisingly, the Indian Ocean Tuna Commission and the Southeast Asian Fisheries Development Center pay more management attention to longtail tuna than does the Western and Central Pacific Fisheries Commission.

Here are some key facts about longtail tuna, although much remains to be discovered about this species:

  • Limited genetic studies indicate at least two stocks – one in coastal northwest India and one in the South China Sea. More studies are required to define the structure of stocks and remove uncertainty over which units to use for stock assessments.
  • Full regional stock assessments are not available. Several local assessments predict the longtail tuna fishery will reach overfished status under the current fishing pressure. No longtail tuna fishery has received certification of sustainability.
  • Most longtail tuna are caught in gillnets, purse seines and troll lines. Usually, the fish are caught in multi-species fisheries, making management of this species difficult. Accurate catch data are difficult to collect.
  • Longtail tuna is sold canned, smoked and fresh, including as sashimi, in domestic markets and on the global market. Longtail tuna canning facilities are located in India, Indonesia, Iran, and Thailand and are supplied with fish captured primarily from purse seines.
  • Longtail tuna is an important recreational fishing species in Australia and Oman.
  • Consumer guides have been inconsistent, partly due to the large data gaps for longtail tuna.

Find out more about longtail tuna by exploring the pages of our profile - Quick Facts, Sustainability, Production, Supply Chains & Markets, Environment & Climate, and Biology.

The profiles were written by an expert team: Duncan Leadbitter, Shane Griffiths, Demian Willette and Thomas Nugroho, and peer reviewed by many other experts (see: Contributors & Reviewers).

After early planning thanks to support from NOAA's FishWatch and potential regional collaborators, AsiaPacific-FishWatch began by starting to prepare full profiles of the 4 key oceanic tuna species, thanks to a grant from the International Seafood Sustainability Foundation (ISSF). These four pilot species comprising of 9 recognised stocks – skipjack, yellowfin, bigeye and albacore tuna - are nearly complete (see Species). AsiaPacific-FishWatch has not yet ventured into other oceanic tunas such as the temperate bluefins (Southern Bluefin and North Pacific Bluefin) and the more coastal (so called neretic) tunas. The four tuna profiles revealed generic lessons for tackling other species, and highly particular insights into where to find expert knowledge on oceanic tunas in the Indian and Western Pacific oceans. The Indian and Western and Central Pacific ocean tuna fisheries produce nearly three quarters of the world's tuna and competition for the fish is increasing. Even as the tuna profiles were composed and reviewed, the transparency of the sources of tuna information improved greatly. Further improvements still are expected as tuna resources and fishing comes under greater public scrutiny, and civil society environmental and labor advocates become more interested and vocal in the tuna management forums.

One lesson from profiling the four oceanic tuna species is that the species differ from each other in important ways, such as in their preferred ocean habitats, growth rates and markets. We hope that the differences as well as similarities become clearer in you read our authoritative profiles, and that this may help to better inform public discussion over actions to ensure sustainability of the resources and social justice in the supply chains. Our profiles are short summaries, barely the tip of an iceberg of expert knowledge and outstanding knowledge gaps.

A quick guide to knowledge on oceanic tunas

The following short guide is presented to share what we have learned after scoping the knowledge iceberg under the water, to help you see more of the iceberg by diving into the depths of knowledge and to keep up with the knowledge of oceanic tunas as it evolves.

Basic identification and biology

A good place to start is with the Food and Agricultural Organization(FAO) and its species fact sheets (see each tuna species page on AsiaPacific-FishWatch),and this link for the species synopsis book.

The IOTC, SPC and ISSF publish handy tuna and bycatch identification guides. Check these out, including extensive guides from the SPC in distinguishing yellowfin and bigeye tuna in all states of freshness and otherwise:

  • Indian Ocean Tuna Commission (IOTC): species identification cards
  • Secretariat for the Pacific Community (SPC): For the most comprehensive guides and handbooks to the identification of yellowfin and bigeye tuna, from fresh to frozen and damaged, see the Secretariat for the Pacific Community FAME Digital Library, and enter "yellowfin" AND "David Itano" (author) into the search boxes to obtain the guides, many in several languages.
  • For ISSF skippers and observers guidebooks online, click this link for the Guidebooks. The guidebooks include identification guides and help on gear practices to avoid and mitigate bycatch.
Stock assessment and stock status reporting is key

In the scientific knowledge base, these four ocean tuna species are each recognized as global, well defined species. They are fished throughout their ranges. Thus the most basic biology - species identification, range and distribution - is established. For the purpose of assessing the status of the stocks, however, much more information than basic biology is needed, starting with defining populations or separate stocks that form the basic units for fisheries assessment. As all species are considered "highly migratory," scientific research has studied the patterns of movement for individual fish, using tags.The types of tags used to mark individual fish started as simple individual markers and have now become highly sophisticated with the advent of electronic archival tags to store and track multiple types of fish and ambient environment information. In the meantime, as tagging and other studies such as genetics, growth and reproductive biology started to reveal more and more about the actual spatial structures of populations, tuna stock assessment experts have had to make working approximations on what to consider as stocks. Hence, for the purposes of assessments, 9 stocks are used, consisting of Indian Ocean (IO) and Western and Central Pacific Ocean (WCPO) stocks in the case of skipjack, yellowfin and bigeye, and, in the case of albacore tuna, IO, Southern Pacific Ocean and Northern Pacific Ocean stocks. Finer spatial resolution and divisions by fishing gear are used in all assessments.

Because stock assessment also requires information on the species growth, life cycle and reproduction, the reports of stock assessments are handy sources to look through for such material. The biological basics are usually succinctly summarized out of the primary research literature consisting of detailed research papers in journals, technical reports and conference papers. For Asia-Pacific, we summarize much of the basic biological knowledge in our species profiles, and provide you with the main sources. Here is where to find these key stock assessment reports:

Global overview:

The ISSF Status of Stocks overviews provide assessments for all oceanic tunas, by stock, based on the regional tuna management organisations' assessments and other credible information on fisheries management measures and environmental issues, especially bycatch of each fishing gear type. ISSF also publishes an overview of bycatch issues in its Status of the Stocks reports.

Indian Ocean:

  1. IOTC Stock Status Dashboard, also links to summary of latest overview of each IO stock 
  2. IOTC Scientific Committee meeting reports and papers
  3. IOTC Home Page 

Western and Central Pacific Ocean:

  1. The Secretariat for the Pacific Community’s Ocean Fisheries Programme website contains a wealth of data and access to publications.
    • More detailed catch and effort data, aggregated for release in the public domain, can be accessed on this link.
    • The WCPFC catalogue of available data can be found at this link.
  2. The SPC also provides an annual overview of stock status. The latest can be downloaded at SPC Oceanfish by clicking on Tuna Stock Status on the right bar.
  3. The Western and Central Pacific Fisheries Commission (WCPFC) Scientific Committee reports and all the meeting papers are online.
  4. The Western and Central Pacific Fisheries Commission (WCPFC) Home Page
  5. The Forum Fisheries Agency Home Page
  6. The Parties to the Nauru Agreement Home Page
  7. The Te Vaka Moana Home Page

Northern Pacific (for Albacore Tuna fishery of the North Pacific)

  1. See the Independent Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean, Albacore Tuna pages.
  2. The Inter-American Tropical Tuna Commission (IATTC) Home Page - also jointly responsible with the WCPFC for regional management of Albacore Fishery of the South Pacific)


Australia shares some of the tuna resources, and also published comprehensive overview of the status of its fish stocks including for bigeye tuna and yellowfin tuna.

Fisheries management and conservation and management measures

For the latest management decisions and up to date documents on the relevant Conservation and Management Measures (CMM), see the following:

  • Western and Central Pacific Fisheries Commission: website, and CMMs
  • Indian Ocean Tuna Commission: website, and CMMs.
  • Inter-American Tropical Tuna Commission (for shared stocks of albacore tuna:): website

Tuna information through the MSC processes

For certified tuna and related fisheries, or those undergoing certification, the Marine Stewardship Council website contains many useful documents. Under the "Track-a-Fishery" tab you will be able to search for fisheries on species, gear, region, etc and find many useful documents from assessment, audits, etc.

Tuna and climate change

The most comprehensive information is in the SPC 2011 book on climate change  - Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change.

Two-thirds of the world’s fish are harvested or farmed in the Asia-Pacific region, yet information on the fish is often difficult to find, piecemeal and confusing. The Asian Fisheries Society and its partners set out to break through this critical information barrier by creating AsiaPacific-FishWatch. “We are bringing together essential and authoritative information on who produces the fish, how they are produced, processed, traded, and eventually end up in the diets of people all around the world,” said the President of the Asian Fisheries Society, Professor Huang (President of Shanghai Ocean University, China). “In this project, we welcome feedback from the public and experts, and collaboration from many partners.”

AsiaPacific-FishWatch ( is developing profiles of the most important types of fish and shellfish produced in the Asia-Pacific region, covering the seas, rivers, lakes and farms of the western and central Pacific ocean and the Indian ocean. The profiles are comprehensive and cover sustainability, production, supply chains, environment and climate, and biology. The aim is to explain Asia-Pacific fish products for consumers, the general public, fish exporters and importers, development agencies, fisheries managers and scientists.

P5100116 sm Pasar Berserhati ManadoThe project is launching with the profile of the region’s skipjack tuna fisheries (see skipjack), and will soon be followed by profiles of yellowfin, bigeye and albacore tuna that are in the final stages of preparation. The skipjack fisheries are among the largest fisheries in the world. The western and central Pacific skipjack fishery supplies the majority of the fish for the world canned tuna market. Susan Jackson, President of the International Seafood Sustainability Foundation (ISSF) explained: “Skipjack schools make up the last remaining truly robust commercially fished stocks of tuna in the world, and protecting this species is especially vital to the economies of nations in the Asia-Pacific region. In order to build consensus around proactive, sustainable management measures for any species of fish, we must have open-access to the wealth of scientific data that exists. Cataloguing this information also helps us to identify voids, which ultimately promotes improved fishery data collection.”

All information in AsiaPacific-FishWatch is reviewed by the top experts in each commodity and subject. It is non-partisan and does not engage in advocacy. Its content emphasizes information relevant to sustainability and people in the supply chain.




Background Information


Twitter: @AsiaPacFish

For more information Contact:

Dr Meryl J Williams, Director AsiaPacific-FishWatch, This email address is being protected from spambots. You need JavaScript enabled to view it.

Lead agency:

Asian Fisheries Society,

c/o Laboratory Marine Biotechnology, Institute of Bioscience

Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, MALAYSIA

In another welcome addition to the availability of information, the SEAFDEC Aquaculture Department has launched its Institute Repository. With hundreds of papers, books, handbooks, extension manuals, articles and newsletter items reaching back to 1978, this collection is also readily searchable and will be further augmented by pictures, videos, presentations and other products.

AsiaPacific-FishWatch is rising to the challenge of finding information on Asia-Pacific fish species, their fisheries and aquaculture and the people who bring them through the supply chain to our bowls and plates. Much of it is not written down, and even some that is can be difficult to find. Therefore, with great joy, I came across the e-print collection of one of the larger fisheries research institute in the region – the Central Marine Fisheries Research Institute of the Indian Council of Agricultural Research. Here is the e-prints address: Loaded with scans of publications going back to 1948, and up to the present, you can search the more than 8,000 papers by year, author, subject, document type or division.  The collection is also indexed in many of the main academic services, including Scientific Commons, Scirus and Google.

At the recently concuded 9th Asian Fisheries and Aquaculture Forum of the Asian Fisheries Society, AsiaPacific-FishWatch was mentioned in the Keynote Address, 'Better Science, Better Fish, Better Life' and presented and discussed in a lively Session of the Forum (see AsiaPacific-FishWatch-9AFAF)


Skipjack (Katsuwonus pelamis, Linnaeus, 1758). Picture: SPC

At the 10th Asian Fisheries and Aquaculture Forum, held from 30 April to 4 May in Yeosu, Korea, I presented a paper on the lessons learned from preparing to soon-to-be released skipjack species profile. The presentation benefited from earlier discussions with Dr Patricia Kailola who undertook most of the preparation of the skipjack profile.

Here is the Abstract, and here is the PPT.