Fisheries and aquaculture are confronted with continuing problems such as climate change, growing human populations, low income of small scale fishers and fish farmers, and competitive production and trading conditions. People should be confronting and discussing the challenges in order to come up with solutions on how we can respond; and the community should be resilient and adaptive in combatting the challenges. We cannot immediately solve some problems, such as overfishing, illegal fishing, depletion of marine resources, as they have deep root causes, but we are learning how to address them. Governments do their best to manage fishery resources to meet these challenges. Decision makers and the public also need to continually listen to new information so that they are equipped with knowledge for sustaining marine and aquaculture resources and protecting people who depend on them for nutrition, livelihood and business. Research is an important information gathering tool that contributes to policy and decision-making. The Asian Fisheries Society and its partners are taking a lead in making new information accessible through its platform AsiaPacific-FishWatch providing essential information on fish harvested or farmed for food in Asia-Pacific. I am pleased that AsiaPacific-FishWatch gives attention in its profiles and posts to the critical social, economic and market character of the value chains. The Asian Fisheries Society emphasises equally social and economic knowledge and biological, physical and technical knowledge.

Prof. Alice Joan G. Ferrer, PhD, President, Asian Fisheries Society

 
 
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ASIAPACIFIC-FISHWATCH

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.

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