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Tracking down expert knowledge on oceanic tunas
Tuesday, 17 March 2015 06:36

Tracking down expert knowledge on oceanic tunas

Written by Meryl J Williams

Woman selling skipjack tuna and other fish on the beach, Malabar Coast, Kerala, India. Photo: Dinesh Kapilly

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.