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Marine fisheries production, although stagnating over the last two decades, has been contributing 55% of global fish production. Increased awareness of fish as a unique nutrient-rich health food, as well as source of quality animal protein, has stimulated the demand for fish in general and marine fish in particular. Over the last two decades, the Asia-Pacific region witnessed a spurt in fishing effort, resulting in dwindling fish catches. Although species richness, high fecundity and varied spawning peaks helped tropical marine fisheries overcome the challenges of higher fishing pressure, high exploitation of commercially important groups has caused serious sustainability concern. Climate change will also likely have considerable impact on fisheries sustainability. For marine harvests to keep growing, mariculture must also receive increased emphasis. Accessing extensive and reliable information on these vast and dynamic oceanic resources remains a challenging task. In this endeavour, the Asian Fisheries Society’s efforts, with support of partners, through the formation of AsiaPacific-FishWatch has been exemplary in generating and disseminating a wealth of information on the region's marine resources. While this comprehensive information base has been helping in drawing up strategic management plans for responsible fisheries by different countries in this region, I sincerely wish that the AsiaPacific-FishWatch will expand its scope and horizon in coming years by associating with more stakeholders involved with the sector.

- Dr. J. K. Jena, President, Asian Fisheries Society

JKJ

Bigeye Tuna

Scientific Name:
Thunnus obesus

Authority:
Lowe, 1839

Common Name:
Bigeye Tuna

Quick Facts

Bigeye tuna live in tropical and warm temperate waters of the Atlantic, Pacific and Indian oceans. They are pelagic and exhibit several dispersion patterns. The Western and Central Pacific Ocean and the Indian Ocean bigeye are each considered single and separate stocks; although considerable mixing occurs, Western and Central Pacific Ocean and Eastern Pacific Ocean bigeye tuna populations are assessed separately for management purposes.

Bigeye tuna form free schools or may swim associated with floating objects such as logs. Juvenile bigeye will form schools with juvenile yellowfin and skipjack tunas. Bigeye tuna tolerate warmer and deeper waters and lower oxygen and salinity levels than other tropical tunas. They may live to at least 15 years of age. They grow more slowly than yellowfin tuna, have lower natural mortality, and are less abundant.

FISHERIES

Bigeye tuna is important in commercial fisheries around the world, accounting for nearly 10% of the world’s catch of major tunas. In the Central and Western Pacific Ocean, 6% of the tuna caught are bigeye and, in the Indian Ocean, 9% are bigeye. Juveniles are caught by both surface gears such as purse seines and, in the Indian Ocean, by gill nets. As valuable adult fish, they are caught by longline and other gears. They are a principal target species of both the large, distant-water longliners from Japan, Korea, China, Taiwan and the smaller, fresh sashimi longliners based in several Pacific Island countries.

SUSTAINABILITY AND MANAGEMENT

The bigeye tuna stock of the Western and Central Pacific appears not to be overfished nor subject to overfishing. However, the stock is considered to remain in a state somewhat more depleted than most other tuna stocks in the Western and Central Pacific. The Indian Ocean bigeye stock is not overfished, nor subject to overfishing. The catch of juvenile bigeye in surface fisheries that target skipjack and yellowfin tuna, e.g., purse seine and gillnet fisheries, is increasing, thus decreasing the biomass of adults in the deeper water longline fisheries and the maximum sustainable yield of the stocks.

Bigeye tuna resources are managed by the Western and Central Pacific Fisheries Commission (WCPFC), the Indian Ocean Tuna Commission (IOTC), and national governments. Sub-regional fishing interest groups, international environmental organisations and market controls also have a strong influence on the governance of bigeye tuna fisheries.

VALUE CHAINS

The meat of bigeye tuna is highly prized and is processed into sashimi in Japan (and western countries). Bigeye is marketed mainly in canned, frozen, or fresh forms. Prices paid for both frozen and fresh product on the Japanese sashimi market are the highest among all the tropical tunas.

FOOD

As food, bigeye is a very good source of low-fat protein and is low in sodium, but has a moderate level of cholesterol. Fat content in bigeye tuna is higher than in other tuna species, yet it is a good choice for low-fat diets.

ECOSYSTEM AND CLIMATE

Bycatch of fishing for bigeye tuna and other pelagic species includes bigeye tuna juveniles, and also sea turtles, sharks, seabirds and other marine fish species and is a significant environmental issue. Among all fishing gears used for bigeye tuna, longlines and gillnets have the greatest bycatch rates.

Longline and purse seine fishing are among the most energy intensive fishing operations as measured by greenhouse gases produced per tonne of fish landed. Also, unless strictly managed, fish canneries may have negative effects on surrounding land and sea environments and the resources they support.

The area of suitable bigeye tuna habitat changes with seasons and with inter-annual climate variability and this is reflected in the catches of bigeye tuna. In the Western and Central Pacific Ocean, the El Niño Southern Oscillation events affect catches of bigeye tuna which are higher during the warmer El Niño period and lower during the cooler La Nina periods.

Global warming affects the distribution and catchability of bigeye tuna stocks which are sensitive to changes in oceanic circulation, the stratification of the water column and water temperature and density.

Sustainability

WILD HARVEST FISHERIES

All bigeye tuna production is from wild harvest fisheries. Bigeye tuna is a moderately fast-growing, widely distributed and very fecund species. It is heavily fished by many different methods and, despite its high productivity, its stocks face future challenges due to a high demand. Both stocks in the Western and Central Pacific Ocean (WCPO) and the Indian Ocean (IO) are currently not overfished. In both oceans areas, the problem of bycatch from longline, gillnets (IO), purse seine fishing with drifting fish aggregating devices (FADs), and the impact of pole and line fishing on baitfish stocks cause environmental problems that are being addressed by several conservation management measures. The effects of these measures are not considered adequately monitored except in the case of the WCPO purse seine fishery.

IUCN Red List Status

Vulnerable (globally) http://www.iucnredlist.org/details/21859/0

Because the maximum sustainable yield (MSY) of the Western and Central Pacific bigeye tuna stock represents more than 20% of the global populations, bigeye tuna is listed as 'vulnerable' globally under Category A2: "Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible."

State of the Stocks and Impacts of Fishing

The updated assessment shows the bigeye tuna stock in the WCPO appears not to be overfished nor subject to overfishing (McKechnie, Pilling & Hampton, 2017). However, the stock is estimated to have declined substantially over most of the assessment period and remains in a state somewhat more depleted than most other tuna stocks in the WCPO (McKechnie et al., 2017). Moreover, it should be noted that at the 2017 Scientific Committee meeting, this assessment was noted to have some degree of uncertainty (Western and Central Pacific Fisheries Commission [WCPFC], 2017). Most of the catch is taken by fishing methods that entail significant bycatch (longlines and surface purse seining on fish aggregating devices (FADs), or, in the case of the small amount of bigeye tuna taken by pole and line, methods that may negatively impact local baitfish species. Monitoring of purse seine fishing is comprehensive and adequate. Monitoring of longline fishing is not as comprehensive as that for purse seine fishing, having lower coverage of logsheet data submitted to the WCPFC and lower observer coverage of fishing trips. However the vessel monitoring system (VMS) coverage of longline fishing, however, is close to 100%.

The bigeye tuna resources of the IO are not overfished, nor subject to overfishing. The majority of the catch is taken by longline, purse seine around FADs and gillnet. These are methods with significant bycatch problems.

The following bigeye tuna stock status information, by ocean, is drawn from the scientific reports of the regional fisheries management organisations and from the International Seafood Sustainability Foundation’s (ISSF) overview of stock status, rankings of management measures and impacts of fishing on bycatch (Status of the Stocks Technical Report).

WCPO BIGEYE TUNA

In stock assessments, bigeye tuna in the WCPO is considered a single stock.

Stock abundance

Yellow - SSB < SSBMSY. The spawning biomass is likely above the MSY level so that it could be rated Green. However, ISSF is rating it Yellow as a precautionary measure given the high uncertainty in the new assessment results.

Fishing mortality

Yellow- F < FMSY. F is likely below the MSY level so that it could be rated Green. However, ISSF is rating it Yellow as a precautionary measure given the high uncertainty in the new assessment results.

Environment

Orange – 44% of the catch is made by longlining. Several mitigation measures are in place (sharks, turtles, sea birds). Monitoring is deficient.

Yellow – 36% of the catch is made by purse seining on floating objects (including FADs). Several bycatch mitigation measures are in place (turtles, sharks). There is 100% observer coverage on part of the purse seine fleet.

Green – 7% of the catch is made with purse seining on free schools, with little impact on non-target species.

Yellow - 3% of the catch is made by pole-and-line fishing, with unknown impacts on baitfish stocks.

IO BIGEYE TUNA

Stock abundance

Green SSB>SSBMSY

Fishing mortality

Green – F<FMSY

Environment

Orange – 56% of the catch is made by longlining. Several mitigation measures are in place (sharks, turtles, sea birds). Monitoring is deficient.

Yellow – 21% of the catch is made by purse seining on floating objects (including FADs). Several bycatch mitigation measures are in place (turtles, sharks).

 Orange – 16% of the catch is made by other gears such as gillnet. There is poor reporting by these fisheries which are thought to have substantial amounts of bycatch.

Green - 7% of the catch is made with purse seining on free schools, with little impact on non-target species.

Certificates for sustainability of wild harvest fishery

Marine Stewardship Council (www.msc.org)

No bigeye tuna fisheries are certified although one fishery, in combination with yellowfin tuna, is under assessment.

Sea (www.friendofthesea.org)

Friend of the Sea does not certify fisheries, but audits and certifies companies in the fish supply chains to adopt selective fishing methods, reduce ecosystem impact and manage within maximum sustainable yield. The certification also deals with quality standards for energy efficiency and social accountability. A list of currently certified fleets for bigeye fishing in the Indian Ocean can be found through this link. and social accountability.

Several conservation and sustainable/fair food organizations also promote sustainable tuna campaigns, e.g., see the Pew Charitable Trusts Global Tuna Conservation campaign.

FISHERIES ASSESSMENTS

The status of bigeye tuna stocks is difficult to assess because each stock is harvested by many different fishing gears, over a wide geographic area with each gear type tending to catch fish of a different size range. Longline fishing mainly harvests adult bigeye tuna whereas purse seines and gillnets harvest a wide size range of bigeye tuna, including many juveniles.

Compared to skipjack and yellowfin tuna stocks, those of bigeye tuna are more vulnerable to overfishing and take longer to recover after a population decline because they are relatively long-lived and mature later than these other tunas. The large and increasing catches of bigeye juveniles by surface fisheries are reducing the size of the spawning stock of large fish caught in the deeper waters by longlines, and reducing the maximum sustainable yield of the whole fishery.

Fisheries catch data, which are essential to bigeye tuna assessments, have several shortcomings. In particular, reporting of bigeye tuna catches is inconsistent among fleets and gears. For some gear types, such as gillnets and those used in artisanal fishing, reporting of catch and effort is limited, e.g., despite their importance, the catches of bigeye tuna in Indonesia, Philippines, and Vietnam are not fully monitored. Bigeye tuna catches are under-reported for several gear types, especially purse seines, because juvenile bigeye join schools and are harvested with other tuna species of similar size, especially skipjack and yellowfin tuna. Log sheets from purse seine fisheries tend to be biased towards recording most small tunas as skipjack. Observer sampling in port and at sea has revealed under-reporting of yellowfin and bigeye of up to 15% (for sets associated with floating objects). Such under-recording of juvenile yellowfin and bigeye tuna occurs both in the WCPO and the IO fisheries and the logbook estimates are adjusted using port - or at sea - samples of fish to help reduce the bias. Difficulties in distinguishing juvenile bigeye from juvenile yellowfin tuna also cause data problems (see Biology).

Western and Central Pacific Ocean

For bigeye tuna in the WCPO, stock assessment and data management services are provided by the Oceanic Fisheries Programme of the Secretariat of the Pacific Community (SPC) and reviewed by the Scientific Committee of the WCPFC. Bigeye assessments are based on catch, effort, fish size and tagging data from the major component fisheries – longline and purse seine fleets - and defined fishing regions of the management area of the WCPFC. Corrections and adjustments are made in the assessment models to account for the estimates of catch composition by species and biases in the monitoring data. Increasing attention is being paid to analyses of data from the fisheries conducted in the intensively fished Indonesian and Philippine waters. The Scientific Advisory Committee of the ISSF takes the WCPFC stock assessments, plus other reliable information, and makes their sustainability assessments based on the estimates of stock abundance, fishing mortality and environmental impact.

Based on annual recent harvests of about 150,000 tonnes, bigeye stock assessment for the Western and Central Pacific Convention Area in 2016 indicated that overfishing is not occurring, however that the stock is estimated to have declined substantially over most of the assessment period and remains in a state somewhat more depleted than most other tuna stocks in the WCPO (McKechnie et al., 2017). The excessive fishing and the increased catch of juvenile bigeye tuna, especially in the tropics, reduced the potential yield of the WCPO bigeye tuna stock.

Longlines take about 42% of the bigeye tuna catch, and purse seines take about 41%, with pole-and-line; handline and other gears taking small shares ((Williams, Terawasi & Reid, 2017). In 2013, the record purse seine catch of bigeye tuna exceeded that of longlines for the first time. The purse seine and other surface fisheries have slightly greater impact on bigeye stocks than does the longline fisheries. The purse seine and Philippines and Indonesian domestic fisheries impact the western Pacific fishery around the equator, and the Japanese coastal pole-and-line and purse-seine fisheries impact the bigeye fishery in the north.

Indian Ocean

For bigeye tuna in the IO, the stock is assessed by the Scientific Committee of the IOTC. The Scientific Advisory Committee of the ISSF takes the IOTC stock assessments, plus other reliable information, to make their sustainability assessments based on the IOTC estimates of stock abundance, fishing mortality and environmental impact. Tag recoveries suggest that bigeye tuna in the Indian Ocean belong to a single stock.

Indian Ocean bigeye tuna stock is not overfished and is not experiencing overfishing. The MSY for the Indian Ocean bigeye stock size is 104,101 tonnes, compared to a recent average of 132,000 tonnes. Catches increased after 2011, however, as the piracy threat in the western Indian Ocean decreased. Stock estimates for the IO are compromised by the lack of detailed catch statistics from some coastal fisheries, the gillnet fisheries of Iran, Pakistan and Sri Lanka and some industrial longline fleets (e.g. from India, Philippines).

FISHERIES MANAGEMENT

Bigeye tuna fisheries are managed by regional fisheries management organizations (RFMOs) and by national governments. Reaching agreement on management measures is difficult due to competing interests of countries and fleets and preferences for different types of management choices, e.g., controls on the number of licenses, total allowable catch limits, vessel day limits, and restricting access to fishing areas.

As for the stock assessments, the management of bigeye tuna fisheries is complicated by the mix of gears and fleets exploiting the stocks in both oceans, and problems in under-reporting of catches of bigeye (and yellowfin), especially in purse seine fisheries.

Industrial tuna fisheries are managed by the WCPFC in the WCPO, the IOTC in the IO, and the Inter-American Tropical Tuna Commission (IATTC) in the Eastern Pacific Ocean (EPO). There is some overlap between the WCPFC and IATTC Convention Areas with respect to management of bigeye tuna. The RFMOs meet annually to consider and endorse recommended management actions. [See Gallery for convention area maps]

Regional associations of countries are increasingly influential in tuna fisheries management, more so in the WCPO than the IO. Individual island countries also manage their tuna resources, through national tuna management plans.

Each of the RFMOs has a scientific committee that provides advice on stock status, monitoring and management implications, using their own and additional scientific expertise. In the case of the WCPFC. SPC is the data management service provider, and holds all of the data used in assessments. WCPFC has the parts of this that are designated as WCPFC data.

Through negotiations, the RFMOs recommend management measures (‘Conservation and Management Measures’ or CMMs) aimed at securing the sustainability of tuna stocks and, more recently, bycatch stocks and the marine environment. However, because the RFMOs use consensus-based decision-making, it is increasingly difficult for agreement to be reached between science, politics and economics on the implementation of effective stock management measures.

In the European Union countries, which are important tuna markets for WCPO and IO tuna, regulations against illegal, unreported and unregulated (IUU) fishing vessels (Council Regulation (EC) No. 1005/2008 and Commission Regulation (EU) No 468/2010) act, in effect, as management drivers.

In addition, campaigns by international environment organizations, such as Greenpeace, the Pew Environment Group and the World Wide Fund for Nature (WWF), advocate against the catch of juvenile bigeye and yellowfin tuna, especially by purse seiners in association with drifting FADs. These campaigns have led to some marketing chains (in Australia, UK, USA) imposing bans or foreshadowing bans on canned tuna harvested around FADs.

Western and Central Pacific Ocean

Although the new assessment is a significant improvement in relation to the previous one, the WCPFC Scientific Committee advises that the amount of uncertainty in the stock status results for the 2017 assessment is higher than for the previous assessment due to the inclusion of new information on bigeye tuna growth and regional structures. The Scientific Committee recommends a precautionary approach that the fishing mortality on bigeye tuna stock should not be increased from current levels to maintain current or increased spawning biomass until the Commission can agree on an appropriate target reference point (WCPFC, 2017). 

While trying to maintain/reduce fishing on bigeye (and yellowfin) tuna, management agencies have to deal with the economic losses that the purse seine fisheries primarily catching skipjack tuna would suffer. With a view to controlling fishing levels on bigeye tuna in the face of increasing fishing pressures and fishing fleet dynamics, the WCPFC continues to develop and encourage implementation of annually revised Conservation and Management Measures (CMM). CMM 2017-01 and its precursors contain articles to control skipjack, yellowfin and bigeye fishing rates by: controlling fishing levels at the average SB/SBF=0 2012-2015 levels (bigeye and yellowfin) and at 50% of the spawning biomass in the absence of fishing (skipjack interim target reference point – CMM 2015-06); management of fishing on FADs and floating objects including seasonal closures; effort controls; high seas controls; retention policies; compliance and observer arrangements; and bigeye longline catch limits by fishing flag states. 

A subset of WCPFC member countries, the Parties to the Nauru Agreement (PNA), also place limits on purse-seine fishing effort within their Exclusive Economic Zones (EEZ) through a ‘vessel day scheme’ (VDS) that only licenses those purse-seine vessels that do not fish in the high seas between 100Nand 200S, including the two tropical high-seas pockets within their region.

Pacific island countries also have to balance domestic development aims for national tuna fishing and onshore processing facilities with sustainable use of tuna resources. Groups of countries have been formed to help foster collective country interests. Regional inter-governmental and industry organizations concerned with tuna in the WCPO are:

Pacific Islands Forum Fisheries Agency (FFA) (https://www.ffa.int/) - (member countries: Australia, Cook Islands, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, Nauru, New Zealand, Niue, Palau, Papua New Guinea, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu and Vanuatu)

Parties to the Nauru Agreement (PNA) (http://www.pnatuna.com/) - (member countries: Federated States of Micronesia, Kiribati, Marshall Islands, Nauru, Palau, Papua New Guinea, Solomon Islands and Tuvalu). The influence of the PNA in tuna management in the WCPF Convention Area has been significant because, as a group, the zones of the member countries host significant yellowfin tuna resources.

TeVaka Moana Arrangement (TVMA) (http://www.tevakamoana.org/) - (member countries: Cook Islands, New Zealand, Niue, Samoa, Tokelau and Tonga).

Pacific Islands Tuna Industry Association (PITIA) (http://www.pitia.org/) - (member countries: Cook Islands, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, Nauru, Niue, Palau, Papua New Guinea, Solomon Islands, Tonga, Tuvalu and Vanuatu).

Indian Ocean

The annual IO catches of bigeye tuna are well below the maximum sustainable yield (MSY) level, and at present immediate management measures are not required. However, continued monitoring and improvement in data collection, reporting and analysis are required to reduce the uncertainty in assessments. The International Seafood Sustainability Foundation recommends that the fishery should be limited entry, accompanied by a closed vessel registry with the aim of reducing the number of fishing vessels targeting the stock.

As yet, the IOTC has not established particular conservation measures for bigeye. More generally, bigeye are subject to CMMs of other species. These measures include providing catch data, limiting fishing capacity and keeping a record of licensed foreign and local fishing vessels, and catch retention, e.g., Resolution 17/04. The main binding conservation measures requires that total catch should not exceed 110,000 tonnes and that vessels longer than 24 m, and smaller vessels if they fish on the high seas, should respect a one-month closure for purse seiners and longliners in an area of size 10°x20°.

In addition to the IOTC management of bigeye and other tuna in the Indian Ocean, the Maldives Seafood Processors and Exporters Association and the Western Indian Ocean Fisheries Directors Forum represent the interests of industry or sub-regional country groups.

AQUACULTURE

Although approval has been given for a yellowfin and bigeye tuna farm off Hawaii, it is not yet operational. Cage grow-out of bigeye is not conducted. The life-cycle of bigeye tuna has not been closed. 


GUIDE TO FURTHER READING

For comments on tuna in IUCN Redlist, see Restrepo et al (2011)

For stock status updates, see the International Seafood Sustainability Foundation’s (ISSF) Status of the Stocks Technical Report, IOTC (2017a) and IOTC Stock Status Dashboard (http://www.iotc.org/science/status-summary-species-tuna-and-tuna-species-under-iotc-mandate-well-other-species-impacted-iotc), Brouwer and others (2017), and McKechnie and others (2017).

For biological and fishery factors affecting bigeye tuna fishery assessments, see Babaran (2006), Colette et al. (2011), Hampton & Williams (2011), Lawson (2010) and Miyake et al. (2010).

For information on the Western and Central Pacific Ocean bigeye tuna assessments, see Brouwer and others (2017), Langley et al. (2011), WCPFC (2017) and Willams and others (2017).

For information on the Indian Ocean bigeye tuna assessments, see IOTC (2017a), IOTC (2016), and ISSF (2018).

For views on achieving effective regional management, see Hamilton et al. (2011) and Polacheck (2012).

For Western and Central Pacific Ocean bigeye tuna management arrangements, challenges and opportunities, including climate see Davies et al. (2011), Hamilton et al. (2011), Brouwer and others (2017), ISSF (2018), Miyake et al. (2010), Restrepo et al. (2014) and Lehodey et al. (2011).

For Indian Ocean management IOTC (2012) and IOTC (2017b).

REFERENCES

  • Babaran RP. 2006. Payao fishing and its impacts to tuna stocks. A preliminary analysis. Western & Central Pacific Fisheries Commission, 2nd Scientific Committee Regular Session, 7-18 August 2006, Manila, Philippines, Paper FT-WP 7. 13 p.
  • Brouwer, S, G Pilling, J Hampton, P Williams, S McKechnie, & L Tremblay-Boyer. 2017. The Western and Central Pacific Tuna Fishery: 2016 Overview and Status of Stocks. Oceanic Fisheries Program, Tuna Fisheries Assessment Report No. 17. Pacific Community: Noumea, New Caledonia.
  • Collette BB and 32 co-authors. 2011. High Value and Long Life—Double Jeopardy for Tunas and Billfishes. Science, 333: 291-292.
  • Davies N, S Hoyle, S Harley, A Langley, P Kleiber & J Hampton. 2011.  Stock assessment of bigeye tuna in the Western and Central Pacific Ocean. Western and Central Pacific Fisheries Commission Scientific Committee Seventh Regular Session, 9-17 August 2011, Pohnpei, Federated States of Micronesia.  WCPFC-SC7-2011/SA- WP-02. 133 p.
  • Hamilton A, A Lewis, MA McCoy, E Havice & L Campling. 2011. Market and industry dynamics in the global tuna supply chain. Forum Fisheries Agency, Honiara. 393 p.
  • Hampton, J & P Williams. 2011. Misreporting of purse seine catches of skipjack and yellowfin-bigeye on logsheets. WCPFC Scientific Committee Seventh Regular Session, 9-17 August 2011, Pohnpei, Federated States of Micronesia. Paper T-WP-02. 11 p.
  • IOTC (Indian Ocean Tuna Commission). 2016. Executive Summary: Status of the Indian Ocean bigeye tuna (Thunnus obesus) resource.  IOTC, Seychelles. http://www.iotc.org/science/status-summary-species-tuna-and-tuna-species-under-iotc-mandate-well-other-species-impacted-iotc .
  • IOTC (Indian Ocean Tuna Commission). 2012. Outcomes of the Fourteenth Session of the Scientific Committee relevant to the Second Technical Committee on allocation criteria. Indian Ocean Tuna Commission Second Technical Committee on Allocation Criteria, Maldives, 4–6 March 2012, IOTC–2012–TCAC02–04[E]. 11 p.
  • IOTC (Indian Ocean Tuna Commission). 2017a. Report of the Tweenteeth Session of the IOTC Scientific Committee Seychelles, 30 December 2017. IOTC–2017–SC20–R[E], 232 p. http://www.iotc.org/documents/report-20th-session-iotc-scientific-committee
  • IOTC (Indian Ocean Tuna Commission). 2017b. Compendium of active conservation and management measures for the Indian Ocean Tuna Commission. IOTC: Seychelles. http://www.iotc.org/cmms
  • ISSF (International Seafood Sustainability Foundation). 2018. ISSF Tuna Stock Status Update, February 2018: Status of the world fisheries for tuna. ISSF Technical Report 2018-02. International Seafood Sustainability Foundation, Washington, D.C., USA. https://iss-foundation.org/about-tuna/status-of-the-stocks/
  • Lawson, T. 2010. Update on the estimation of selectivity bias based on paired spill and grab samples collected by observers on purse seiners in the Western and Central Pacific Ocean. Sixth Regular Session of the Scientific Committee of the Western and Central Fisheries Commission, 10-19 August 2010, Nuku’alofa, Tonga. Working Paper SC6-WP02. 19p.
  • Lehodey P, J Hampton, RW Brill, S Nicol, I Senina, B Calmettes, HO Portner, L Bopp, T Ilyina, JD Bell and J Siebert. (2011). Vulnerability of oceanic fisheries in the tropical Pacific to climate change. In: Bell JD, Johnson JE, Hobday AJ (eds) Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change.  Secretariat of the Pacific Community, Noumea, New Caledonia, pp. 433–492.
  • McKechnie, S, G Pilling & J Hampton. 2017. Stock assessment of bigeye tuna in the western and central Pacific Ocean. Scientific Committee Thirteenth Regular Session, 9-17 August 2017. Western and Central Pacific Fisheries Commission: Rarotonga, Cook Islands. https://www.wcpfc.int/system/files/SC13-SA-WP-05%20%5Bbet-assessment%5D%20REV1.pdf
  • Miyake MP, P Guillotreau, CH Sun & G Ishimura. 2010. Recent developments in the tuna industry: stocks, fisheries, management, processing, trade and markets. FAO Fisheries and Aquaculture Technical Paper. No. 543. Rome, FAO. 125 p.
  • Polacheck T. 2012. Politics and independent scientific advice in RFMO processes: a case study of crossing boundaries. Marine Policy, 36: 132-141.
  • Restrepo VR, BB Collette & WW Fox. 2011. IUCN tuna assessments. 7 Jully 2011. Link
  • Restrepo V, L Dagorn, D Itano, A Justel-Rubio, F Forget and JD Filmalter. 2014 A summary of bycatch issues and ISSF mitigation initiatives to-date in purse seine fisheries, with emphasis on FADs. ISSF Technical Report 2014-1, International Seafood Sustainability Foundation, Washington DC, USA.
  • WCPFC (Western and Central Pacific Fisheries Commission). 2017. Summary report of the thirteenth regular session of the Scientific Committee. Rarotonga, Cook Islands, 9-17 August 2017. https://www.wcpfc.int/system/files/0_SC13%20Summary%20Report%20%28Adopted%20Version%20-%2017Nov2017%29.pdf
  • Williams, P, P Terawasi & C Reid. 2017. Overview of tuna fisheries in the Western and Central Pacific Ocean, including economic conditions – 2016. WCPFC-SC13-2017/GN WP-01. Western and Central Pacific Fisheries Commission: Rarotonga, Cook Islands. https://www.wcpfc.int/system/files/GN-WP-01%20Overview%20of%20WCPFC%20Fisheries_1.pdf 

Production

SPECIES IMPORTANCE

Bigeye tuna is of major commercial interest, caught primarily for sashimi (larger fish) and to a lesser extent, for canning (small fish).

Bigeye tuna occurs in the tropical and subtropical waters of the Atlantic, Indian and Pacific Oceans, but is absent from the Mediterranean Sea. Production is from all of these regions, Japan and the Republic of Korea being the major countries reporting catches.

In the Western and Central Pacific and Indian Oceans, bigeye tuna is targeted in the industrial and smaller scale tuna longlining fisheries and is taken also in non-targeted catches in the purse-seine and pole and line fisheries. Juvenile bigeye tuna caught in the purse seine fishery is either canned (although not invariably and may be diverted to fish meal, flakes etc. because of blood spots in the meat, and increasing traceability requirement for one species in the can as occasionally verified by DNA) and fresh in local markets; mature adults from the longline fishery generally are sold as sashimi or good quality steaks. Juvenile bigeye and yellowfin tuna are similar in appearance and as a result bigeye tuna is likely to be counted as yellowfin. Bigeye tuna catches, therefore, may be slightly underreported.

More than 80% of the world’s bigeye tuna is caught in the Indian and Pacific Oceans (Western and Central and Eastern areas). The catch was highest in the Western and Central Pacific Convention Area (around 150,000 t); followed by around 100,000 t in the Eastern Pacific Ocean area, and around 90,000 t in the Indian Ocean (recent five year averages).

FISHING METHODS

Bigeye tuna is caught predominately by longline and purse seine (both targeted and non-targeted). Other gears also used, but accounting for a significantly smaller proportion of the catch, are pole and line (limited), handline and troll, and gillnet.

Western and Central Pacific

Bigeye tuna of sashimi size and quality is the most valuable of the tropical tunas and is the principal target of large distant-water longliners which freeze catches, and of the smaller, locally-based fresh sashimi vessels (National Oceanic and Atmospheric Administration, 2007). Within the Pacific Ocean, bigeye tuna is distributed through the basin but the bulk of the catch is made towards the eastern and western ends of the ocean basin. Bigeye tuna fisheries in the Western and Central Pacific Ocean (WCPO) are diverse, ranging from small-scale artisanal operations in the coastal waters of Pacific states, Indonesia and Philippines, to industrial purse-seine, pole and line, and longline operations in the exclusive economic zones of Pacific states and in international waters.

The majority of the catch in the WCPO is taken in equatorial areas, by both purse-seine and longline. The longline catch is predominately taken in the central Pacific, contiguous with the important traditional bigeye tuna longline area in the eastern Pacific. Some of the longline catch is within sub-tropical areas, for example, east of Japan and off the east coast of Australia.

The domestic surface fisheries of the Philippines and Indonesia take large numbers of small bigeye in the range 20-50 cm. In addition, large numbers of 25-75 cm bigeye tuna are taken in purse seine fishing on Fish Aggregating Devices (FADs), which along with the fisheries of the Philippines and Indonesia account for the bulk of the catch by number.

Large bigeye tuna are rarely taken in the WCPO purse-seine fishery, and only a relatively small amount comes from the handline fishery in the Philippines. This contrasts with large yellowfin tuna, which, in addition to the longline catch, is also taken in significant amounts from unassociated schools in the purse-seine fishery and in the Philippines and Indonesian handline fishery.

By weight, the longline fishery accounts for most of the bigeye tuna catch. Bigeye tuna sampled in the longline fishery are predominantly adult fish, with a mean size of approximately 130 cm; most fish are between 80 and 160 cm. Bigeye tuna are generally caught in waters of about 10-15°C, at 100–400m depth, although substantial commercial catches are made where the temperature range is 13–27°C and at depths of at least 200-400m. The best fishing is usually a few days before, during and a few days after a full moon, taking advantage of the fact that large bigeye come close to the surface (50 to 100 m) to feed at night in equatorial waters.

The area fished is determined to some extent by access agreements and the cost of those agreements. The Japanese longline distant water fleet predominately catch bigeye tuna, the majority of which is taken in high seas areas (60% in 2015 and close to 60% on average 2011-2015). A large proportion of Japanese longline distant water fleet catch also occurs within Japan, FSM, Marshall Islands, Palau and Solomon Islands EEZs. Effort shifts seasonally tending north of 10oN and towards high seas areas and the Japan EEZ. Other distant water fleets, such as the Taiwanese large-scale tuna longline fleet also catch the majority of its tuna (mostly albacore and bigeye) in the high seas (average catch in 2011-2015 was 74%). Effort has also shifted between the high seas and within EEZs (and also between EPO and WCPO) for the Korean longline fleet reflecting changes in access arrangements.

Bigeye tuna are also caught by handlining, often around anchored FADs, or by longlining in domestic fisheries in some regions, such as Indonesia, Philippines, and operated by large artisanal fishing vessels. Their catches of quality bigeye tuna are exported as quality fresh chilled product.

Eastern Pacific Ocean

Despite little gene flow between populations of bigeye tuna in the Eastern and Western Pacific Ocean (Philippines and Ecuador), bigeye in the Pacific Ocean appear to comprise a single Pacific-wide population (see more in BIOLOGY). The majority of the bigeye tuna catch in the Eastern Pacific Ocean (EPO) was initially taken by longline vessels, however with the expansion of purse-seine fishing on fish-aggregating devices since 1993, the purse-seine fishery has taken an increasing component of the bigeye catch. Subsequently, fishing mortality of juvenile fish has increased alongside the expansion of the purse-seine fishery catching tuna associated with FADs, although the average size taken is relatively larger in the EPO than the WCPO relating to the shallower EPO thermocline.

Effort has shifted towards the EPO for the distant water Japanese longline fleet with the trend for fishing outside of PICs EEZs and a much higher quota in the EPO (32,372 mt cf. 16,860 mt in 2017).

Indian Ocean

In the Indian Ocean (IO), the distant-water longline fishery commenced operation during the early 1950s and reached a peak in the late 1990s–early 2000s. During the mid-2000s, the total annual bigeye tuna catch declined considerably, primarily due to a decline in the longline catch in the western equatorial region in response to the threat of piracy off the Somali coast. This has recovered somewhat over the following years.

Industrial fisheries account for the majority of catches of bigeye tuna including from vessels equipped with deep-freezers (-600C) and fresh longline and purse seine fisheries by Indonesian, Taiwanese, Chinese, Seychelles, and EU-Spanish fleets mainly in the Western Indian Ocean but also in the Eastern Indian Ocean. The fishery by deep-freezing longliners is dominated by Taiwanese fleets accounting for as much as 40-50% of the total longline catch in the IO. Bigeye tuna caught by purse seiners in the IO are dominated by the EU and Seychelles fleets and are mainly small juvenile bigeye tuna (around 5 kg).

The sizes exploited in the IO range from 30 cm to 180 cm fork length. Newly-recruited fish are primarily caught by the purse seine fishery on floating objects where they form mixed schools with skipjack tuna and juvenile yellowfin and are mainly limited to surface tropical waters, while larger fish are found in sub-surface waters.

Bigeye tuna are also caught by handlining, often around anchored FADs, or by longlining in domestic fisheries in some regions, such as Maldives, Sri Lanka and (presumably) other coastal IO States, and operated by large artisanal fishing vessels. Their catches of quality bigeye tuna are exported as quality fresh chilled product.

Gillnet fisheries also take a substantial catch but reporting is minimal.

INDUSTRIAL-SCALE FISHERIES

The industrial scale longline industry is characterised by two main vessel types – large-scale distant water vessels (supplying frozen tuna) and small-medium scale offshore vessels (supplying fresh tuna). Longline vessels targeting albacore or other species may also supply incidental bigeye catch to the fresh sashimi market.

Bigeye tuna caught in the longline fishery (and Japanese pole and line fishery) are placed in ultra-low temperature (ULT) freezers capable of reaching temperatures of -55oC to -60°C for storing catch, and after arriving at port, may be air-freighted to Japanese, European or US markets where they are sold as sashimi or fresh chilled fish or sold and transported to local markets.

SMALL-SCALE FISHERIES

Artisanal fisheries are defined as those undertaken by fishing boats having overall length (LOA) of less than 24 m and operated full-time within the EEZ of their flag States. In most coastal States such vessels engage in fully commercial fishing – notably in the 18 member States of the IOTC, and in Indonesia, the Philippines and Vietnam. Fishing fleets in developing countries are very diverse, some fleets are multipurpose and artisanal or traditional in nature. Unless hand-lining at night, truly subsistence fleets are less likely to catch bigeye tuna in commercial quantities.

The domestic Indonesian and Philippine fisheries employ various gears for catching bigeye (targeted and non-targeted) including ring net, pole and line, handline, longline, and purse seine. These fisheries, such as the Philippine domestic purse seine and ring net fisheries, are FAD-based fisheries and, within Philippine waters, mainly catching juvenile tunas. The domestic fisheries catch juvenile bigeye tuna from 15 to 78 cm in length (average 28 cm). Enhancements have been made to some small scale longline vessels to improve their freezing and fish hold capacity to access high-quality markets and increase autonomy at sea (e.g. Taiwanese longline fleet).

RECREATIONAL FISHING

Bigeye tuna is an excellent sport fish. Recreational fishing methods are: trolling deep with squid, mullet or other small baits, and artificial lure and live bait fishing in deep waters.

AQUACULTURE

Although approval had been given for a yellowfin and bigeye tuna farm off Hawaii, it never began commercial operations before closing down in 2017. The Research Institute for Mariculture in Gondol, Bali conducted research from 2003 to 2010 to analyse to develop techniques for tuna species resource enhancement however has since closed. Cage grow-out of bigeye tuna is not conducted. The life-cycle of bigeye tuna has not been closed.

GUIDE TO FURTHER READING

Note: Details of all sources are given in References below.

On species importance, see: FAO Species Fact Sheet for bigeye tuna http://www.fao.org/fishery/species/2498/en, and ISSF (2018).

On fishing methods, see for the WCPO, see: National Oceanic and Atmospheric Administration (2007), Brouwer and others (2017), Leroy and others (2013), Hanamoto (1987), Farley and others (2006), Lehodey and others (2011), Boggs (1992), Beverly and others (2003 in McCoy & Gillett, 2005), Campling and others (2017), Babaran (2006), and Harley and others (2009).

For the EPO, see IATTC (2016), and Campling and others (2017).

For the IO, see: IOTC (2016), IOTC (2017), and IOTC (2011).

For industrial-scale fishing, see: Hamilton and others (2011).

For small-scale fishing, see: Miyake and others (2010), USAID (2017), WCPFC (2017), and Campling and others (2017).

For recreational fishing, see: the International Gamefishing Association (www.igfa.org).

General descriptions of the main gear types used for the capture of bigeye tuna can be found at: http://www.fao.org/fishery/fishtech/1010/en.

REFERENCES

  • Babaran, RP. 2006. August. Payao fishing and its impacts to tuna stocks: A preliminary analysis. In Second regular scientific meeting. WCPFC. Manila (pp. 7-8).
  • Boggs, CH. 1992. Depth, capture time, and hooked longevity of longline-caught pelagic fish: timing bites of fish with chips. Fish. Bull., 90, pp.642-658.
  • Brouwer, S, G Pilling, J Hampton, P Williams, S McKechnie & L Tremblay-Boyer. 2017. The Western and Central Pacific tuna fishery: 2016 overview and status of stocks. Noumea, New Caledonia: Pacific Community. https://www.wcpfc.int/node/30158
  • Campling, L, A Lewis, & M McCoy. 2017. The Tuna Longline Industry in the Western and Central Pacific Ocean and its Market Dynamics. Honiara: Pacific Islands Forum Fisheries Agency. http://www.ffa.int/system/files/Campling-Lewis-McCoy%202017%20The%20Tuna%20%20Longline%20Industry.pdf
  • FAO (Food and Agriculture Organisation of the United Nations) Fisheries and Aquaculture Department. 2017. Species fact sheets: Thunnus obesus. http://www.fao.org/fishery/species/2498/en
  • Farley, JH, NP Clear, B Leroy, TL Davis, & G McPherson. 2006. Age, growth and preliminary estimates of maturity of bigeye tuna, Thunnus obesus, in the Australian region. Marine and freshwater Research, 57(7), pp.713-724.
  • Hamilton, A., A Lewis, M.A. McCoy, E Havice, & L Campling. 2011. Market and industry dynamics in the global tuna supply chain. Honiara, Solomon Islands: Pacific Islands Forum Fisheries Agency. https://www.ffa.int/system/files/Global%20Tuna%20Market%20%26%20Industry%20Dynamics_Part%201a.pdf
  • Hanamoto, E. 1987. Effect of oceanographic environment on bigeye tuna distribution. Bull. Japan. Soc. Fish. Oceanogr, 51:213-216.
  • Harley S, S Hoyle, A Langley, J Hampton & P Kleiber. 2009. Stock assessment of bigeye tuna in the Western and Central Pacific Ocean. Western and Central Pacific Fisheries Commission Scientific Committee Fifth Regular Session, 10-21 August 2009, Port Vila, Vanuatu. WCPFC-SC5-2009/SA-WP-4. 98 p.
  • IATTC (Inter-American Tropical Tuna Commission). 2016. Tunas, billfishes and other pelagic species in the Eastern Pacific Ocean in 2015. La Jolla, California: Inter-American Tropical Tuna Commission.https://www.wcpfc.int/system/files/GN-WP-02%20IATTC%20Tunas-billfishes-and-other-pelagic-species-in-the-EPO-2015.pdf
  • IOTC (Indian Ocean Tuna Commission). 2011. Executive Summary: status of the Indian Ocean bigeye tuna (Thunnus obesus) resource. IOTC-2011-SC14-09. 9 p.
  • IOTC (Indian Ocean Tuna Commission). (2017). Status summary for species of tuna and tuna-like species under the IOTC mandate, as well as other species impacted by IOTC fisheries. Victoria Mahé, Seychelles: Indian Ocean Tuna Commission. http://www.iotc.org/science/status-summary-species-tuna-and-tuna-species-under-iotc-mandate-well-other-species-impacted-iotc
  • IOTC (Indian Ocean Tuna Commission). (2016). Stock assessment of bigeye tuna in the Indian Ocean for 2016 — model development and evaluation IOTC-2016-WPTT18-20. Victoria Mahé, Seychelles: Indian Ocean Tuna Commission. http://www.iotc.org/documents/stock-assessment-bigeye-tuna-indian-ocean-2016
  • ISSF (International Seafood Sustainability Foundation). 2018. Status of the world fisheries for tuna. February 2018. ISSF Technical Report 2018-02. International Seafood Sustainability Foundation, Washington, D.C., USA.
  • Leroy, B, J Scutt Phillips, S Nicol, GM Pilling, S Harley, D Bromhead, S Hoyle, S Caillot, V Allain, & J Hampton. 2013. A critique of the ecosystem impacts of drifting and anchored FADs use by purse- seine tuna fisheries in the western and central Pacific Ocean. Aquat. Living Resour. 26, 49–61.
  • Lehodey P, J Hampton, RW Brill, S Nicol, I Senina, B Calmettes, HO Portner, L Bopp, T Ilyina, JD Bell & J Siebert. (2011). Vulnerability of oceanic fisheries in the tropical Pacific to climate change. In: Bell JD, Johnson JE, Hobday AJ (eds) Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change. Secretariat of the Pacific Community, Noumea, New Caledonia, pp. 433–492.
  • McCoy, MA & RD Gillett. 2005. Tuna Longlining by China in the Pacific Islands: a description and considerations for increasing benefits to FFA member countries. Pacific Islands Forum Fisheries Agency.
  • Miyake MP, P Guillotreau, CH Sun & G Ishimura. 2010. Recent developments in the tuna industry: stocks, fisheries, management, processing, trade and markets. FAO Fisheries and Aquaculture Technical Paper. No. 543. Rome, FAO. 125 p.
  • National Oceanic and Atmospheric Administration. 2007. Fishery Management Plan for U.S. West Coast Fisheries for Highly Migratory Species. As amended. Appendix A: Description of the fishery. Portland, Oregon: National Oceanic and Atmospheric Administration. http://www.pcouncil.org/wp-content/uploads/2017/03/HMS_AppA_pt1.pdf
  • USAID (United States Agency for International Development). (2017). Value Chain Assessment: General Santos City, Philippines. Manila, Philippines: United States Agency for International Development/Regional Development Mission for Asia. 
  • WCPFC (Western and Central Pacific Fisheries Commission). 2017. Western and Central Pacific Fisheries Commission Tuna Fishery Yearbook 2016. Noumea, New Caledonia: Oceanic Fisheries Programme Pacific Community. https://www.wcpfc.int/statistical-bulletins

Supply Chains

POST HARVEST

Bigeye tuna is one of the most valuable tuna species and is the most highly targeted species, followed by yellowfin tuna and, to a lesser extent, albacore. Bigeye tuna generally has less fat than bluefin tuna but is popular for its bright red flesh.

CANNING

Bigeye tuna is predominately used in the sushi and sashimi market, however, some bigeye tuna is canned by default. In 2007, approximately 2% of total canned tuna was bigeye tuna.

SASHIMI AND OTHER PRODUCTS

Japan is the major global market for sashimi quality tuna (around 80% of global consumption in 2010). In 2014, bigeye accounts for 38% of the total supply volume (imports and landings) of sashimi grade tuna. In 2015, over 90% of bigeye landings to Japan is frozen.

Longliners and some purse seiners, especially those from Japan, have ultra-low temperature (ULT) freezing capability at -60 or -35-40o freezing capacity (ULT commands a higher price premium) allowing for the production of sashimi-quality tuna. Most fish caught by purse seining is canned but larger fish such as bigeye tuna caught by Japanese purse seine vessels with ULT freezers is sold as a product termed ‘purse seine special’ on the lower-quality sashimi market, still fetching a higher value than that for canning. Fish that is unsuitable for top or export markets is sold on domestic markets.

Adult bigeye tuna is caught by coastal longlining, pole-and-line, and handline and is sold fresh chilled, generally as sashimi or as fresh steaks.

Eating fresh tuna has been popular in the large United States market since the late 1990s. The most popular tuna fresh is the so-called ‘ahi’, the Hawaiian name for bigeye tuna, but ‘ahi’ may be either yellowfin or bigeye tuna.

COMMON MARKET NAMES

The FAO names for bigeye tuna: bigeye tuna (English); Thon obese (French); and Patudo (Spanish). Bigeye tuna is known by many local common names (e.g., see FishBase – http://www.fishbase.org – for lists). In the USA, the Hawaiian word for both yellowfin and bigeye tuna, "ahi," has been used as a marketing tool irrespective of fish origin and has gained general acceptance at the wholesale and retail level.

NUTRITIONAL VALUE

Fat content in bigeye tuna is higher than in other tuna species, yet, relative to other animal-based foods, it remains a good choice for low-fat diets. The fish has firm, red-pink flesh and a mild flavour. A c.100 g. serving contains 108 calories, roughly 500 mg of omega-3 fatty acids and 1 g of fat.

Nutrition Facts, 1 serving, of weight 113g

CALORIES 130
PROTEIN 27g
FAT, TOTAL 2g
SATURATED FATTY ACIDS, TOTAL 0.5g
CARBOHYDRATE 0g
SUGARS, TOTAL 0g
FIBER, TOTAL DIETARY 0g
CHOLESTEROL 45mg
SELENIUM 160% daily value
SODIUM 70 mg

TRADE AND MARKETS

Japan is the world’s principal market for fresh-chilled and frozen sashimi-grade tuna accounting for around 80% of the global sashimi consumption in 2010. The USA is the second market in volume for sushi and sashimi with an estimated 8-10 percent of global sashimi consumption. Sushi consumption is now a global trend and consumers in more countries are eating it. Longline-caught bigeye tuna are exported fresh or frozen mainly to sashimi markets in Japan, the USA and Europe. Sashimi-grade portions of catches are offloaded in ports with good air-freight connections to Japan and other markets, while the non-sashimi grade portion is either sold in local markets, processed into export-grade value-added fresh and frozen tuna products, or frozen whole round for export or shipping back to home ports.

Indonesia has long been a major exporter of fresh-chilled sashimi grade tuna, mainly to U.S. markets. A large number of Taiwanese and Indonesian joint-venture vessels have been based in Jakarta and Benoa and mostly fish in the Indian Ocean. The Philippines, Vietnam and Fiji are other major bigeye exporters to the U.S.

Recent national and international management controls for longline vessels catching bigeye tuna and other species, such as yellowfin tuna, require registration and traceability certificates for import clearance to the market countries, especially Japan, the EU and the USA.

EMPLOYMENT, SOCIAL FACTORS AND GENDER

Much of the fishing for bigeye tuna takes place outside exclusive economic zones and so employment and social factors concern mainly those in countries of vessel owners, crews and markets. In the case of the longline fisheries, developing countries, such as those in the Pacific and Indian Ocean, have gained only small economic returns. Longline vessels are said to have low profit margins, including from rising operating costs such as from fuel that are not accompanied by rising tuna prices.

Men comprise the fishing crews on tuna fishing vessels. The majority of cannery production workers are women although men are engaged in heavy tasks. Men have a significant role in bigeye tuna production, simply because the adult fish are large, from catching, moving fish around at landing places and in processing facilities, and in some fresh chilled and sashimi markets (e.g. in Japan).

In the Philippines and Indonesia, small bigeye tuna are usually sold in local markets by women. Women have established niche spaces in the Fish Port Tambler Complex of General Santos City, Philippines.

Women are beginning to enter non-traditional areas of work, for example, as observers and tuna taggers on board fishing vessels – e.g. in the Solomon Islands and Fiji.

FISHING

Labour on fishing vessels has received much greater attention in recent years as labour and human rights groups have uncovered many instances of rights abuses, especially on those vessels that spend protracted periods at sea, such as longliners and even large purse seine vessels. The operating costs squeeze on such vessels has led to extensive hire of migrant crew, some quite young, from poor backgrounds in countries such as Cambodia, Indonesia, Myanmar, Philippines and Vietnam who are paid little and who work under bonded labour conditions. Some are trafficked as forced labour.

Large-scale distant water longline fishing vessels present the most challenging labour conditions as the vessels can be at sea for as long as 18 months and the work entails long hours under arduous conditions. Although nominally covered by the new ILO Work in Fishing Convention No. 188(2007) that came into force on 17 November 2017, more minimum requirements are needed: minimum age; medically fitness; conditions of service such as adequate crewing and rest periods, employment contracts, repatriation, recruitment and placement; accommodation and food; and, medical care, health protection and social security.

Socially responsible labour conditions are becoming recognised as reasons, alongside conservation issues, for restricting tuna imports, including of high value species such as bigeye tuna. Flag states and market ports, e.g., Taiwan, Hawaii (USA) have had to pass domestic laws addressing hiring of foreign crew and protecting the workers’ rights.

Social standards for supply chains free of forced and child labour are beginning to enter the requirements of the certifying bodies such as the Marine Stewardship Council (MSC), Pacifical (Parties to the Nauru Agreement MSC certified fisheries), and OPAGAC (the fishing association representing the Spanish purse seine tuna fleet). Major tuna retailers are now requesting social audits although, in the case of key bigeye tuna markets, Japanese and other Asian sashimi markets are not applying much pressure for longline social standards. In 2017, Thai Union Group introduced a fishing vessel improvement program and vessel code of conduct to provide guidance to vessels from which the company sources as well as improve labour and ethical performance in the fishing sector.

PROCESSING FACILITIES

In the bigeye tuna value chain, women are mostly engaged in fish processing (canneries) and trimming and preparing fish pouches and steaks for export; they also engage in domestic and non-commercial marketing of small fish. Women may join men as production managers and the like in processing operations.

GUIDE TO FURTHER READING

Note: Details of all sources are given References below.

For comprehensive post harvest information see Campling, Lewis & McCoy (2017).

For canning, see: Hamilton and others (2011).

For sashimi and other products, see: Campling and others (2017), Miyake and others (2010), and Hamilton and others (2011).

For common market names, see: FAO bigeye tuna Species Fact Sheet (http://www.fao.org/fishery/species/2498/en) and for many local common names, see FishBase for lists (http://www.fishbase.org).

For nutritional value, see FishChoice (2018) and Fishwatch (2017).

For trade and markets, see: Campling and others (2017), FAO (2017) and Hamilton and others (2011).

For employment, social factors see: Campling and others (2017).

For gender, see Tuara & Passfield (2011), Ram-Bidesi (2010), and Pavo & Digal (2017).

On labour in fishing, see: Campling and others (2017), de Coning (2011).

REFERENCES

Environment, Climate

All fishing gears have some level of environmental effect. Under the FAO Code of Conduct for Responsible Fishing, the fishing sector is expected to minimize its effects on the environment in order to sustain the resources and environment on which it relies. For bigeye tuna caught in surface and deep waters by a wide variety of fishing methods, bycatch is one of the most observable environmental effects, especially from fishing by longlines, gillnets and by purse seines on floating objects (including fish aggregating devices - FADs). In the case of purse seine vessels setting on FADs, bigeye tuna is not the target species and juvenile bigeye tuna are species are themselves regarded as bycatch (see - Sustainability).

Air and water pollution from fishing and fish processing are other environment concerns.

Ocean climate and global warming affect the distribution and catchability of bigeye stocks.

EFFECTS OF FISHING ON OTHER SPECIES

Bigeye tuna are caught by purse-seine, longline, pole-and-line and troll line in the Western and Central Pacific Ocean (WCPO), and by gill nets, longline, purse seine, pole and line, handline and troll line in the Indian Ocean (IO).

Fishing gear used to catch bigeye tuna does not come into contact with the seafloor and so does not directly affect the benthic environment.

Longline fishing targeting bigeye tuna (and albacore tuna) has a substantial bycatch of non-tuna species that can make up from more than half to two-thirds of the total catch, depending on the type of longline fishing. The main fish bycatch species in the WCPO include sharks, billfish, pelagic stingrays, and other finfish including moonfish (opah, Lampris guttatus), although their frequency in catches varies across the region.

Some longline vessels target sharks, especially when tunas are scarce. Sharks are targeted for their fins and meat. Longline crews often significantly top up their income from the sales of shark fins. Each year in the WCPO and IO, tens of thousands of individual sharks are caught and finned. In the WCPO, common bycatch sharks are: blue shark (Prionace glauca), silky shark (Carcharhinus falciformis), oceanic whitetip shark (Carcharhinus longimanus), mako sharks (Isurus spp), thresher sharks (Alopias spp), porbeagle shark (Lamna nasus), winghead hammerhead (Eusphyra blochii), scalloped hammerhead (Sphyrna corona), great hammerhead (Sphyrna mokarran) and smooth hammerhead (Sphyrna zygaena). Many shark species have experienced steep declines in catch in recent years, most likely due to high fishing mortality.

Conversely, sharks cause considerable damage to tuna on hooks in the longline fishery, and can reduce the value of the catch.

To reduce the catch and mortality of sharks, changes in longline gear are being used or investigated. These include changes in hook type and hook position in the water, replacing wire traces with nylon leaders and improving survival by better handling practices.

In the case of sea turtles, the loggerhead turtle is of most concern as bycatch in longline operations in the WCPO, although all species are at some risk. In the IO, all species of sea turtles are at risk of being caught by longlines.

Many species of seabirds are also caught by longlines in the WCPO, including especially large albatrosses in the higher latitudes. In the IO, breeding areas of species of albatross and petrel overlap extensively with the longline fishing grounds but records of bird catches are incomplete for many fleets. Mitigation methods are based on mapping the areas of greatest overlap of seabirds and fishing. Setting lines at night to avoid birds, weighting the lines for faster sinking and attaching streamers to keep the birds away are being encouraged to reduce bird mortality but more research is required to determine the most effective methods.

Marine mammal catches on longlines targeting bigeye tuna are not significant in most areas of the WCPO. In the IO, fishing for bigeye tuna in the northwest causes significant mortality of marine mammals.

Of the surface fisheries that catch juvenile bigeye, gill nets, used extensively in the IO, are of greatest concern for bycatch. This fishing is poorly monitored and traps a wide range of non-target species.

For purse-seine vessels targeting skipjack tuna, but which also catch juvenile bigeye tuna, the percentage of the catch comprised of non-tuna species is relatively low: 1.6% for nets set around FADs and 0.4% for sets on free-swimming schools not associated with FADs. In the WCPO purse seine fisheries, the bycatch of non-tuna species includes mainly silky shark, mackerel scad, mahi mahi (dolphin fish, Coryphaena hippurus), frigate mackerel, oceanic triggerfish and rainbow runner.

The bycatch from pole-and-line and troll fisheries is minimal. However, in the past when pole-and-line fishing was much more common than it is today, the stocks of the small pelagic fish species used as live bait were considered at risk of local depletion in some Pacific Island countries.

The Western and Central Pacific Fisheries Commission (WCPFC) and the Indian Ocean Tuna Commission (IOTC) have conservation and monitoring measures for bycatch mitigation and monitoring. Specific conservation and management measure address bycatch issues for sea turtles, sharks (including finning), sea birds, cetaceans, other finfish and reporting provisions to support bycatch research and monitoring. The International Seafood Sustainability Foundation (ISSF) conducts regionally specific by-catch mitigation training workshops for purse seine vessel skippers.

IMPACTS ON AIR AND WATER

All tuna fishing vessels rely on fossil fuel; their exhaust fumes and refrigerant gases contribute to greenhouse gases (GHG) emissions and thus global warming.

The estimated total carbon footprint of purse seine-caught tuna (all species) in 2009 was approximately 1,530 kg CO2 per tonne of tuna landed. The GHG emissions associated with catching tuna by purse-seine vessels, storing it on board and delivering whole fish to processing plants, are three times greater than the emissions stemming from the processing, packaging and transport of the resulting products.

The amount of fuel used to catch a tonne of tuna is greater for longline vessels than for purse-seine vessels. The carbon footprint of longline tuna products in increased further by the air freight required to deliver sashimi-grade tuna and other fresh tuna products to markets because GHG emissions are much higher for airfreight than for sea freight.

Bigeye tuna is a sought after species for sashimi and fresh rather than frozen product receives a premium price. Frozen and canned tuna transported by truck or container vessel have a lower carbon footprint than do fresh, chilled tuna transported by air.

For bigeye that are canned, the water, energy use and greenhouse gas emissions issues common to other canned tuna apply.

EFFECTS OF ENVIRONMENT ON BIGEYE

The life cycles of all tuna species depend on oceanic circulation: currents determine the location of spawning grounds, the dispersal and successful survival and growth of larvae, juveniles and adults, and the distribution of their prey. The availability of the nutrients in the tuna food web, and the location of water at suitable temperatures and levels of dissolved oxygen determine the tuna distribution and abundance.

In the WCPO, the El Niño Southern Oscillation (ENSO) is an oscillation between a warm (El Niño) and a cooler (La Niña) state. ENSO events have significant effects on bigeye tuna catches by surface and deep water fishing gears.

In the surface fisheries, catchability of bigeye tuna is lower during La Niña events when the thermocline is deeper and the surface layer of water is greater in volume, making bigeye less vulnerable to surface fishing gear. Bigeye tuna can tolerate lower levels of dissolved oxygen (O2) than other tunas and can feed at depths greater than 500 m. Longline catch rates of bigeye are also lower during La Nina events. The reverse occurs during El Niño events when the thermocline is shallower and surface temperatures higher. Surface fishery catch rates are higher during El Niño episodes and longline catch rates of bigeye tuna are also increased.

In the Eastern Indian Ocean off Java, ENSO events appear to have similar effects on bigeye tuna catch rates to those in the WCPO. In the IO, the Indian Ocean Index is a climate oscillation between a warmer and cooler state that better predicts warm and cold events in the Western Indian Ocean than do ENSO events. For bigeye longline catches in the IO, bigeye tuna catches tended to increase during warm events, although catch rates are affected by targeting practices.

EFFECTS OF CLIMATE CHANGE ON BIGEYE

Because of their mobility, bigeye tuna are likely to respond to increased sea surface temperatures and lower ambient O2 caused by the increased temperature by moving to areas within their preferred temperature ranges, both for spawning and feeding. Models that use projected changes in temperatures, currents, and food chains in the open ocean predict that future concentrations of bigeye are likely to be found further to the east than they are today. In the western equatorial Pacific, bigeye are likely to lose spawning grounds due to the projected high temperatures. The possible loss of equatorial spawning habitat may be compensated for by increased larval survival in the sub-tropics. Juvenile and adult fish, however, may have to contend with inferior habitat as sea surface temperatures rise and increase stratification of the water column, reducing availability of nutrients and prey, and as lower O2 concentrations occur near the surface.

Overall, by 2035, bigeye tuna catches are projected to decrease by a small amount (usually <5%), depending on the assumptions, in 17 of the 22 Pacific Island countries’ territories. By 2100, in some countries, larger declines of up to 30% are projected under some scenarios.


GUIDE TO FURTHER READING

Note: Details of all sources are given in References below

For tuna bycatch and discards in the IO tuna fisheries, see David Ardill and others (2011).

Shelley Clarke and others (2014) provided a global overview, by ocean, of longline bycatch and mitigation measures for sharks, sea turtles, seabirds, marine mammals and non-tuna finfish. For the WCPO, Shelton Harley and others (2014) reported on bycatch and non-tuna catch.

On shark catches in the WCPO tuna fisheries, see Shelley Clarke (2011), Shelley Clarke and others (2011) and Tim Lawson (2011). Mike McCoy & Bob Gillett (2005) provided insights into the shark targeting and importance of shark catches for crews on Chinese vessels. Makoto Peter Miyake and others (2010) reported on shark damage to tuna on longlines. The WCPFC’s Conservation and Management Measure (CMM) 2010-07 lists shark species of concern. For information on fishing gear modifications to reduce longline shark catch and bycatch see Don Bromhead and others (2013), Pew Marine Environment Group (2011), and Peter Ward and others (2007).

On baitfish for pole and line fishing in Solomon Islands and Fiji, see Steve Blaber and others (1993). For bycatch conservation and monitoring measures of the WCPFC, see https://www.wcpfc.int/conservation-and-management-measures, for IOTC see http://www.iotc.org/cmms; for a recent compendium of measures, see ISSF (2014).

Peter Tyedmers and Robert Parker (2011) provide a preliminary assessment of the impacts of bigeye tuna fishing and supply chain on air and water. The report from UNEP (2000) provided information on the environment impacts of tuna processing.

Effects of climate change on the foodwebs that support bigeye tuna and other species of tuna are reviewed by Robert Le Borgne and others (2011). For effects of climate change on bigeye tuna fish stocks see Patrick Lehodey and others (2011), who also projected catches under two future scenarios for greenhouse gas emissions. For ENSO effects on bigeye tuna catches in the EIO, see Mega Syamsuddin and others (2013), and for IO F. Ménard and colleagues.

REFERENCES

  • Ardill, D., D. Itano and R. Gillett. 2011. A Review of Bycatch and Discard Issues in Indian Ocean Tuna Fisheries. IOTC-2012-WPEB08-INF20. 44 p.
  • Blaber, SJM, DA Milton & NJF Rawlinson. 1993. Tuna Baitfish in Fiji and Solomon Islands, proceedings of a workshop, Suva, Fiji, 17-18 Aug. 1993. Canberra: Australian Council for International Agricultural Research (ACIAR) Proceedings 52.
  • Bromhead, D, J Rice, & S Harley. 2013. Analyses of the potential influence of four gear factors (leader type, hook type, “shark” lines and bait type) on shark catch rates in WCPO tuna longline fisheries. WCPFC-SC9-2013/EB-WP-02 rev 1.
  • Clarke SC. 2011. A status snapshot of key shark species in the Western and Central Pacific and potential mitigation options. Western and Central Pacific Fisheries Commission Scientific Committee Seventh Regular Session, 9-17 August 2011, Pohnpei, Federated States of Micronesia. WCPFC–SC7–2011/EB–WP–04. 37 p. /
  • Clarke S, S Harley, S Hoyle & J Rice. 2011. An indicator-based analysis of key shark species based on data held by SPC-OFP. Western and Central Pacific Fisheries Commission Scientific Committee Seventh Regular Session, 9-17 August 2011, Pohnpei, Federated States of Micronesia. WCPFC-SC7-2011/EB-WP-01 89 p.
  • Clarke, S, M Sato, C Small, B Sullivan, Y Inoue, & D Ochi. 2014. Bycatch in longline fisheries for tuna and tuna-like species: a global review of status and mitigation measures. FAO Fisheries and Aquaculture Technical Paper No. 588. Rome, FAO. 199 p.
  • Harley, S, P. Williams, S. Nicol and J. Hampton. 2014. The Western and Central Pacific Tuna Fishery: 2012 Overview and Status of Stocks. Secretariat to the Pacific Community, Oceanic Fisheries Programme. Tuna Fisheries Assessment Report 13, Noumea, New Caledonia. 31 p.
  • ISSF (International Seafood Sustainability Foundation). 2014. ISSF Tuna Stock Status Update, 2014: Status of the world fisheries for tuna. ISSF Technical Report 2014-09. International Seafood Sustainability Foundation, Washington, D.C., USA.
  • Lawson, T. 2011. Estimation of Catch Rates and Catches of Key Shark Species in Tuna Fisheries of the Western and Central Pacific Ocean Using Observer Data. Western and Central Pacific Fisheries Commission Scientific Committee Seventh Regular Session, 9-17 August 2011, Pohnpei, Federated States of Micronesia. WCPFC–SC7–2011 / EB–IP–02. 52 p.
  • Lehodey P, J Hampton, RW Bril, S Nicol, I Senina, B Calmettes,HO Pörtner, L Bopp, T Ilyina, JD Bell & J Sibert. 2011. Vulnerability of oceanic fisheries in the tropical Pacific to climate change. pp 433-492, in JD Bell, JE Johnson & AJ Hobday (eds), Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change. Secretariat of the Pacific Community, Noumea, New Caledonia.
  • Le Borgne, R., V Allain, SP Griffiths, RJ Matear, AD McKinnon, AJ Richardson & JW Young. 2011. Vulnerability of open ocean food webs in the tropical Pacific to climate change. pp 189-250, in JD Bell, JE Johnson & AJ Hobday (eds), Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change. Secretariat of the Pacific Community, Noumea, New Caledonia.
  • McCoy MA & RD Gillett. 2005. Tuna longlining by China in the Pacific Islands: a description and considerations for increasing benefits to FFA member countries. FFA Report 05/13. Gillett, Preston & Associates Inc. 80 p.
  • Ménard, F, F Marsac, E Bellier and B Cazelles. 2007. Climatic oscillations and tuna catch rates in the Indian Ocean: a wavelet approach to time series analysis. Fisheries Oceanography 16:95–104.
  • Miyake MP, Guillotreau P, Sun CH & Ishimura G. 2010. Recent developments in the tuna industry: stocks, fisheries, management, processing, trade and markets. FAO Fisheries and Aquaculture Technical Paper. No. 543. Rome, FAO. 125 p.
  • Pew Environment Group. 2011. Recommendations to Kobe III joint tuna RFMO meeting. http://www.pewtrusts.org/en/research-and-analysis/fact-sheets/2010/06/16/shark-bycatch-in-tuna-fisheries (accessed -5 February 2015).
  • Syamsuddin, ML, SI Saitoh, T Hirawake, S Bachri, AB Harto. 2013. Effects of El Niño–Southern Oscillation events on catches of bigeye tuna (Thunnus obesus) in the eastern Indian Ocean off Java. Fishery Bulletin 111:175-188.
  • Tyedmers, P. and R. Parker. 2012. Fuel consumption and greenhouse gas emissions from global tuna fisheries: preliminary assessment. ISSF Technical Report 2012-­‐03. International Seafood Sustainability Foundation, McLean, Virginia, USA.
  • UNEP (United Nations Environment Programme). 2000. Cleaner Production Assessment in Fish Processing. United Nations Environment Programme. www.unep.fr/shared/publications/pdf/2481-CPfish.pdf (accessed 7 February 2015)
  • Ward P, Lawrence E, Darbyshire R & Hindmarsh S. 2007. Large-scale experiment shows that nylon leaders reduce shark bycatch and benefit pelagic longline fishers. Fisheries Research, 90: 100-108.
  • WCPFC’s Conservation and Management Measure (CMM) 2010-07

Biology

DESCRIPTION

Bigeye is a large tuna with a long, robust, and tapered body. Its pectoral fins are moderately long (22-31% of fork length) in fish larger than 110 cm fork length, but very long (30% or more of fork length) in smaller fish. It differs from yellowfin tuna (Thunnus albacares), in its colour, and by: 1) 23-31 rakers on the first gill arch (26-34 in yellowfin), 2) striated ventral surface of the liver (not striated in yellowfin), and 3) approximately equal liver lobes (in yellowfin, the right lobe is much longer than the other lobes). The second dorsal and anal fins of bigeye tuna do not grow as long as those of yellowfin tuna.

At a comparable size, the swim bladder of a bigeye tuna is larger than that of a yellowfin tuna.

The back is dark metallic blue and the sides and belly are whitish; when the fish is alive, an iridescent blue band runs along the sides. The first dorsal fin is dark yellow and the second dorsal and anal fins are pale yellow. The finlets are bright yellow with a black edge. The tail is plain and does not have a white trailing edge (as has albacore, T. alalunga).

ECOSYSTEM ROLE

Together with the other species of tropical tuna, bigeye tuna is near the top of the pelagic food chain. Tunas typically follow the daily vertical movement of their preferred prey (micronekton), moving to deeper habitats during the day and to shallower habitats at night. The physiology of bigeye allows them to feed deeper in the water column and for longer periods than other tropical tunas. Bigeye tuna foraging behavior also changes as they grow, with larger individuals able to more frequently use deeper habitats.

Predators of bigeye include other tunas, sharks, dolphins, sailfish, marlins, and toothed whales.

HABITAT AND DISTRIBUTION

Bigeye tuna occur worldwide in tropical and subtropical waters but are absent from the Mediterranean Sea. In the Western and Central Pacific and Indian oceans, bigeye are found between Latitudes 40º N and 40 ºS.

They are found predominantly in tropical open ocean ecoregions, in waters extending from the surface to below the mixed layer and thermocline. In coastal waters, bigeye tuna are most commonly found in waters around the bottom of the mixed layer, which varies with place and season. [See gallery for bigeye tuna distribution map and diagram]. Bigeye are rarely found over shallow coastal shelves where the ocean depth is less than about 50 m.

Despite little gene flow between populations of bigeye in the eastern and western Pacific Ocean (Philippines and Ecuador), bigeye in the Pacific Ocean appear to comprise a single Pacific-wide population. Recent analyses of bigeye tagging studies supports these genetic observations, with little mixing observed between fish tagged in the extreme east and west of the Pacific. Higher rates of mixing were observed in the central Pacific. The bigeye tuna showed little dispersal by latitude (N-S), some regional retention and some large eastward longitudinal movements. From the tagging results, three possible Pacific stocks may be inferred but for management purposes, to the present, the bigeye tuna eastern and western Pacific fisheries are assessed separately.

During mark-recapture studies, bigeye tuna in the Pacific have been recovered up to 5,372 nautical miles from their release points, after periods at liberty from one to nearly five years. In the Pacific Ocean, three types of movement patterns are identified: (1) fish that reside within 1,000 nautical miles of their release location, (2) fish that are residents, yet undertake excursions outside the residence area, to which they return, and (3) fish that are nomadic and have other movement patterns. In the Indian Ocean, tagged juveniles moved 657 nautical miles, on average, between release and recapture. In general, however, the understanding of bigeye movement and its relationship with fish size is still poor.

The higher tolerance of bigeye tuna to variation in water temperature and O2 levels allows them to use a wide range of ocean habitats. As with other tuna, the blood circulation system of bigeye tuna has a heat exchanger that rapidly lessens heating and cooling rates. This enables these fish to maintain muscle temperatures significantly above those of the environment; increasing both their swimming efficiency and the range of temperatures in which they can live. Adult bigeye tuna (>100 cm FL (fish length)) can live in water with dissolved oxygen (O2) levels as low as 1.5 ml/L and in cool water (50C - 150C). However, bigeye tuna spend little time in water temperatures below 70C and oxygen levels less than about 2 ml/L.

The characteristic daily behavior of bigeye tuna is to feed above the thermocline in the mixed layer starting at dusk, and descend below the thermocline at dawn to feed at depth in cooler waters. Bigeye tuna appear to have flexible feeding strategies, enabling them to succeed in a patchy environment. Given this flexibility, the behavior of individual fish can vary considerably with location, season, moon phase and food availability. Juvenile bigeye can school at the surface underneath floating objects, along with yellowfin and skipjack tunas. Older bigeye tuna are less commonly found near floating surface objects.

GROWTH, REPRODUCTION AND DIET

Although much is known about bigeye tuna growth, variations in growth rates between fish in different stock assessment areas and across the full size range are still under study, using several methods and sometimes integrating these: growth increments on otoliths (ear bones), tag-recapture and length frequency analysis. In the WCPO, IO and other oceans, younger bigeye tuna are relatively fast-growing but growth slows in the second year of life, when the fish are between 40 and 70 cm FL.

In the WCPO, bigeye tuna growth appears to be faster than that in other oceans up to the size of the growth slow down and slower than that in other oceans for fish at sizes larger than about 100 cm. Except for the very early growth, in the Western Indian Ocean, bigeye tuna growth rates were similar to those of bigeye tuna in the Western Pacific Ocean. The bigeye tuna in the eastern Indian and south-west Pacific oceans display different growth rates from those in the Eastern Pacific Ocean.

In the WCPO, bigeye tuna mature after 2.5 years and begin spawning at 3-4 years of age (about 100-130 cm FL, 30 Kg). Indian Ocean bigeye tuna mature at three years of age at about 100 cm FL. Maximum size is 200 cm FL, commonly to 180 cm FL, and maximum weight is 210 kg.

In the Pacific Ocean, many fish survive until 8-16 years of age. The life span of bigeye in the Indian Ocean has been estimated at 15 years.

Bigeye tuna are batch spawners, capable of spawning daily and releasing batches of about 1 to nearly 10 million eggs. The eggs and larvae are pelagic.

Bigeye spawn year-round in warm surface waters (>24°C), although spawning is generally restricted to the summer months of December to January in the tropical western Pacific and Indian oceans. However, spawning also takes place in June in the eastern Indian Ocean, and mature females are found off north-eastern Australia in August. Spawning occurs between about 30°N and 20°S in the Western Pacific. Spawning is undertaken mainly at night, between about 1900 h and 0400 h.

Bigeye tuna forage successfully, during day and night, on a range of organisms. The diet of bigeye tuna includes shallow-water squid, crustaceans and fish (mullet, sardines, small mackerels), as well as deep water micronekton (squid, euphausiids and mesopelagic fish).


GUIDE TO FURTHER READING

Note: Details of all sources are given in References below.

For bigeye tuna descriptions, see Collette 2001, Schaefer (1999), Bertrand and Josse (2000), the Indian Ocean Tuna Commission (IOTC) species identification card (http://www.iotc.org/science/species-identification-cards) and the International Game Fish Association (http://www.igfa.org/).

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 the use of habitat, see Musyl et al. (2003) and Brill et al. (2005). Predators are given in FishBase (www.fishbase.org).

For descriptions of habitat and geographic distribution, see Reygondeau et al. (2012), Collette (2001) and Lee, et al. (2005). Grewe & Hampton (1998), IOTC (2011) and Schaefer et al. (2015) address stock structures, movement and dispersion.

For information on biology, physiology and distribution, see Musyl et al. (2003), Boye et al. (2009), Lehodey et al. (2011).

For daily behavior patterns and their variability, see Evans et al. (2008) and Schaefer and Fuller (2010). For juvenile schooling behavior, see Collette (2001) and IOTC (2011).

For growth see: Lehodey et al. (1999), Farley et al (2006) and Fonteneau and Hallier (2015) on growth rates of young fish. For comparative growth rates by ocean from tagging studies, see Fonteneau and Hallier (2015); for IO growth Stéquert & Conand (2004); for WCPO and EPO, Farley et al. (2006), Nicol et al. (2011), and Fonteneau and Hallier (2015).

For information on maximum size, see Lehodey et al. (1999), Collette (2001), and Fishbase (www.fishbase.org). For life span and age information, see Farley et al. (2006), Lehodey et al. (1999), Harley et al. (2009) and IOTC (2011).

On maturation and reproduction of bigeye tuna, see Schaefer et al. (2005); for WCPO, see Lehodey et al. (1999), Farley et al. (2006), SPC (2009), and Sun et al. (2013); and for IO, see IOTC (2011). For bigeye tuna diet, see Musyl et al. (2003), Evans et al. (2008), and Collette (2001).

REFERENCES

  • Bertrand, A, and E Josse. 2000. Tuna target-strength related to fish length and swimbladder volume. ICES Journal of Marine Science: Journal du Conseil 57:1143-1146.
  • Boye J, M Musyl, R Brill & H Malte. 2009. Transectional heat transfer in thermoregulating bigeye tuna (Thunnus obesus) - a 2D heat flux model. The Journal of Experimental Biology, 212:3708-3718.
  • Brill RW, KA Bigelow, MK Musyl, KA Fritsches & EJ Warrant. 2005. Bigeye tuna (Thunnus obesus) behaviour and physiology and their relevance to stock assessments and fishery biology. Collective Volume of Scientific Papers of the ICCAT, 57(2):142-161.
  • Collette BB. 2001. Tunas (also, albacore, bonitos, mackerels, seerfishes, and wahoo). pp 3721-3756, in K.E. Carpenter & V.H. Niem (eds), FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Vol. 6: Bony Fishes Part 4 (Labridae to Latimeriidae), Estuarine Crocodiles, Sea Turtles, Sea Snakes and Marine Mammals. Rome, FAO.
  • Evans K, A Langley, NP Clear, P Williams, T Patterson, J Sibert, J Hampton & JS Gunn. 2008. Behaviour and habitat preferences of bigeye tuna (Thunnus obesus) and their influence on longline fishery catches in the western Coral Sea. Canadian Journal of Fisheries & Aquatic Sciences, 65:2427-2443.
  • Farley J, NP Clear, B Leroy, TLO Davis TLO & G McPherson. 2006. Age, growth and preliminary estimates of maturity of bigeye tuna, Thunnus obesus, in the Australian region. Marine and Freshwater Research, 57: 713-724.
  • Fonteneau, A, and JP Hallier. 2015. Fifty years of dart tag recoveries for tropical tuna: A global comparison of results for the western Pacific, eastern Pacific, Atlantic, and Indian Oceans. Fisheries Research 163:7-22.
  • Grewe P & J Hampton. 1998. An assessment of bigeye (Thunnus obesus) population structure in the Pacific Ocean, based on mitochondrial DNA and DNA microsatellite analysis. Report, CSIRO Marine Research. 34 p.
  • Harley S, S Hoyle, A Langley, J Hampton & P Kleiber. 2009. Stock assessment of bigeye tuna in the Western and Central Pacific Ocean. Western and Central Pacific Fisheries Commission Scientific Committee Fifth Regular Session, 10-21 August 2009, Port Vila, Vanuatu. WCPFC-SC5-2009/SA-WP-4. 98 p.
  • IOTC (Indian Ocean Tuna Commission). 2011. Executive Summary: status of the Indian Ocean bigeye tuna (Thunnus obesus) resource. IOTC-2011-SC14-09. 9 p.
  • Lee PF, IC Chen IC & WN Tzeng. 2005. Spatial and temporal distribution patterns of bigeye tuna (Thunnus obesus) in the Indian Ocean. Zoological Studies, 44(2): 260-270.
  • Lehodey, P, J Hampton & B Leroy. 1999. Preliminary results on age and growth of bigeye tuna (Thunnus obesus) from the western and central pacific ocean as indicated by daily growth increments and tagging data. Standing Committee on Tuna and Billfish 12 16-23 June 1999, Tahiti. Working Paper BET-2, 18 p.
  • Lehodey P, J Hampton, RW Bril, S Nicol, I Senina, B Calmettes, HO Pörtner, L Bopp, T Ilyina, JD Bell & J Sibert. 2011. Vulnerability of oceanic fisheries in the tropical Pacific to climate change. pp 433-492, in JD Bell, JE Johnson & AJ Hobday (eds), Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change. Secretariat of the Pacific Community, Noumea, New Caledonia.
  • Musyl MK, RW Brill, CH Boggs, DC Curran, TK Kazama & MP Seki. 2003. Vertical movements of bigeye tuna (Thunnus obesus) associated with islands, buoys, and seamounts near the main Hawaiian Islands from archival tagging data. Fisheries and Oceanography, 12: 152-169. [abstract]
  • Nicol, S, S Hoyle, J Farley, B Muller, S Retalmai, K Sisior, & A Williams. 2011. Bigeye tuna age, growth and reproductive biology (Project 35). WCPFC-SC7-2011/SA- WP -01, Revision 1 (3 August 2011).
  • Reygondeau, G, O Maury, G Beaugrand, JM Fromentin, A Fonteneau & P Cury. 2012. Biogeography of tuna and billfish communities. Journal of Biogeography, 39:114-129.
  • Schaefer, KM. 1999. Comparative study of some morphological features of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tunas. Bulletin/Inter.-American Tropical Tuna Commission, 21:491-525.
  • Schaefer, KM, DW Fuller, & N Miyabe. 2005. Reproductive biology of bigeye tuna (Thunnus obesus) in the eastern and central Pacific Ocean. Inter-American Tropical Tuna Commission. Bulletin 23:3-31.
  • Schaefer, K & D. Fuller. 2010. Vertical movements, behavior, and habitat of bigeye tuna (Thunnus obesus) in the equatorial eastern Pacific Ocean, ascertained from archival tag data. Marine Biology 157:2625-2642.
  • Schaefer, K, D Fuller, J Hampton, S Caillot, B Leroy, & D Itano. 2015. Movements, dispersion, and mixing of bigeye tuna (Thunnus obesus) tagged and released in the equatorial Central Pacific Ocean, with conventional and archival tags. Fisheries Research 161:336-355.
  • SPC, OFP (Secretariat of the Pacific Community’s Oceanic Fisheries Programme). 2009. Tuna fisheries in the western and central Pacific: an update. SPC Fisheries Newsletter #129 - May/August 2009: 8-9.
  • Stéquert B & F Conand F. 2004. Age and growth of bigeye tuna (Thunnus obesus) in the Western Indian Ocean. Cybium, 28:163-170.
  • Sun, CL, SZ Yeh, YJ Chang, HY Chang & SL Chu. 2013. Reproductive biology of female bigeye tuna Thunnus obesus in the western Pacific Ocean. Journal of Fish Biology, 83: 250-271.

Links

Contributors, Reviewers

Compilers

The information on albacore tuna compiled and edited by the following people.

  • Quick Facts: Patricia Kailola, Tarlochan Singh, Victoria Jollands
  • Sustainability: Patricia Kailola, Victoria Jollands, and Tarlochan Singh
  • Production: Victoria Jollands, Patricia Kailola, and Tarlochan Singh
  • Supply Chains & Markets: Victoria Jollands, Patricia Kailola, and Tarlochan Singh
  • Environment & Climate: Patricia Kailola, Tarlochan Singh, and Victoria Jollands
  • Biology: Patricia Kailola, Tarlochan Singh

Editing, all pages: Meryl Williams

Information Provided by the Following

  • John Hampton (Secretariat for the Pacific Community - SPC)
  • Johann D. Bell, SPC (Pacific Island consumption patterns, climate change)
  • Lindsay Chapman, SPC (Pacific Island consumption patterns)
  • Simon Hoyle – SPC
  • Peter Williams – SPC
  • Peter Nichols (CSIRO, Australia) nutritional value
  • David Wilson IOTC – Indian Ocean material in Sustainability, Environment and Climate, and Biology profiles
  • FAO – for use of figures
  • Fishbase team, Philippines

Reviewers

Drafts of the presentation were reviewed by the following:

  • David Wilson (IOTC) – Indian Ocean: Sustainability, Environment and Climate, Biology
  • John Hampton (SPC) – Western and Central Pacific Ocean: Sustainability
  • Simon Nicol, (SPC): Environment and Climate, Biology
  • Johann Bell – Sustainability, Environment and Climate, Biology
  • Tony Lewis – Production, Supply Chains & Markets

Photographs and Graphics

  • Gabriel Reygondeau - Institut de Recherche pour le De´veloppement (IRD) – use of figure
  • Secretariat for the Pacific Community
  • Johann Bell (SPC)
  • International Seafood Sustainability Foundation
  • David Itano
  • Food and Agriculture Organization
  • Media Commons

Funding and Support

Funding to prepare the skipjack information was provided by the International Seafood Sustainability Foundation (iss-foundation.org) and the Asian Fisheries Society (www.asianfisheriessociety.org).

In-kind support has been provided by the host organizations of those who provided information and reviewed drafts.