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Thunnus orientalis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA ACTINOPTERYGII PERCIFORMES SCOMBRIDAE

Scientific Name: Thunnus orientalis
Species Authority: (Temminck & Schlegel, 1844)
Common Name/s:
English Pacific Bluefin Tuna
French Thon Rouge, Thon Bleu du Pacifique
Spanish Atún Aleta Azul del Pacífico, Atún Cimarrón
Synonym/s:
Orcynus schlegelii Steindachner, 1884
Thunnus saliens Jordan & Evermann, 1926
Thunnus thynnus subspecies orientalis Temminck & Schlegel, 1844
Thynnus orientalis Temminck & Schlegel, 1844
Taxonomic Notes: The Pacific (Thunnus orientalis) and Atlantic (Thunnus thynnus) populations are now recognized as separate species (Collette 1999).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2011-02-18
Assessor/s: Collette, B., Acero, A., Boustany, A., Canales Ramirez, C., Cardenas, G., Carpenter, K.E., Chang, S.-K., Chiang, W., Di Natale, A., Die, D., Fox, W., Graves, J., Hinton, M., Juan Jorda, M., Minte Vera, C., Miyabe, N., Montano Cruz, R., Nelson, R., Restrepo, V., Schaefer, K., Schratwieser, J., Serra, R., Sun, C., Uozumi, Y. & Yanez, E.
Reviewer/s: Russell, B. & Polidoro, B.
Justification:
This a is highly commercial and valuable species. The stock is considered fully exploited, with catches being relatively stable in the past five to 10 years. Estimates of spawning stock biomass (SSB) have shown an increasing trend over the past 21–27 years (three generation lengths). It is listed as Least Concern. However, given the conflicting management advice from different RMFO's, it is recommended that one management body take responsibility for this species.
For further information about this species, see TUNAS_SkiJumpEffect.pdf.
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Geographic Range [top]

Range Description: This species is present throughout the Indo-Pacific. It is a temperate species that also extends into tropical waters. There are records of this species in New Zealand and French Polynesia. More information is needed to confirm this species distribution to these areas, and there is no evidence of spawning in these areas.
Countries:
Native:
Australia; Canada; China; Ecuador; Guam; India; Japan; Korea, Republic of; Marshall Islands; Mexico; Northern Mariana Islands; Papua New Guinea; Philippines; Russian Federation; Taiwan, Province of China; United States
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – eastern central; Pacific – northeast; Pacific – northwest; Pacific – southeast; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: FAO worldwide reported landings show a increase from 1,452 tonnes in 1950 to 31,542 tonnes in 1961, then gradually decreasing to less 8,049 tonnes in 1984. Landings from 1985 to present have fluctuated, but are relatively stable between 5,800–10,000 tonnes from 1985–2006 (FAO 2009). In the Pacific, the catch from 2000–2004 is reported as 16,000–29,000 tonnes/year, and the status of the stock is Fully Exploited (Majikowski 2007). In April 2011, the Southwest Fisheries Science Center of the US National Marine Fisheries Service found that overfishing is occurring on Pacific Bluefin Tuna but that the stock was not in an overfished condition (Menashes 2011).

For the entire Pacific, half of the stock is caught in the Eastern Pacific Ocean, and the other half in the Western Pacific Ocean. The Eastern Pacific is likely half of the Pacific catch, but no good stock assessment exists. Based on FAO data, there is an apparent decrease in total landings for the Eastern Pacific between 1994–2004 from approximately 9,000 mt to approximately 3,000 mt, but data from the Inter-American Tropical Tuna Commission (IATTC) over the same time period is relatively constant at around 2,000–3,000 mt with some peaks of 8,000 mts and 9,000 mts in 2004 and 2006 (IATTC 2008). The majority of the catch is off of Baja California. Catch numbers have naturally fluctuated based on population migration. This species spawns in the Sea of Japan, and an unknown proportion migrates to the Eastern Pacific, stays a few years, and then migrates back to the Western Pacific. Fluctuations in catch in the Eastern Pacific are thus results of the proportion of migrants that come to the Eastern Pacific. Similarly, the consecutive years of above average catches in the Eastern Pacific (mid-1950s to mid-1960s) and below-average catches (early 1980s to early 1990s) could be due to consecutive years of above-average and below-average recruitments (IATTC 2010).

Based on a 2008 stock assessment (ISC 2008), evaluation of the stock is not straightforward. From the late 1980s, spawning stock biomass (SSB) has recovered to about 30,000 t by the mid-1990s, and then declined again to 20,000 t. At this level, SSB in 2005 was near the median level over the assessment period (1952–2004). Total catch fluctuated widely in the range of 9,000–40,000 t during the assessment time period, while recent catches have been near the average for the assessment period (~22,000 t). Over the entire catch history, annual catch has never attained the equilibrium catch at FMSY (45,000 t).

Based on updates to this assessment that were conducted in 2009 (ISC 2009) and 2010 (ISC 2010), the estimated spawning biomass in 2008 declined from the last estimate of 2006 and is in the range of 40–60% of the historically observed spawning biomasses. Average fishing mortality from 2004–2006 (F2004-2006) has increased for all age classes, and 30-year projections predict that at F2004-2006 median spawning biomass is likely to decline to levels around the 25th percentile of historical spawning biomass with approximately 5% of the projections declining to or below the lowest previously observed spawning biomass. At F2002-2004 median spawning biomass is likely to decline in subsequent years but recover to levels near the median of the historically observed levels. In contrast to F2004-2006, F2002-2004 had no projections (0%) declining to the lowest observed spawning biomass (ISC 2010).

Based on linear regression of estimated SSB (ISC 2008, ISC 2009), the stock shows an increasing trend over the past 21–27 years (from 1984–2006 and from 1986–2006).
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: This is an epipelagic and usually oceanic species, but seasonally comes close to the shore. It tolerates wide temperature ranges and forms schools by size, sometimes with other Scombrids. It migrates between June and September in a northward direction along the coast of Baja California, Mexico and California. A model of migration is presented by Bayliff (1994). It is found to 550 m depth. It is a voracious predator that feeds on a wide variety of small schooling fishes or squid, and also eats crabs and less sessile organisms (Collette and Nauen 1983).

Longevity may be as long as 15 years (Hsu 2000) or 26 years (Shimose 2009). Spawning occurs between Japan and the Philippines in April, May, and June, off southern Honshu in July, and in the Sea of Japan in August.  The sex ratio is about 1:1. Size at first maturity is 150 cm FL and 60 kg at an age of approximately five years. Batch fecundity increases with length, from about five million eggs at 190 cm FL to about 25 million eggs at 240 cm FL (Collette 2010, Schaefer 2001, Sawada et al. 2005, Chen et al. 2006).

Based on maturity and longevity studies (Collette et al. 2011), the generation length of this species is estimated to be between 7–9 years.

The all-tackle game fish record is of a 325 kg fish caught off Westport, New Zealand in 2007 (IGFA 2011).
Systems: Marine

Threats [top]

Major Threat(s): In the Northern Pacific, this species is fished with set net, trolling, and purse seines. Most of the catch in the Eastern Pacific is taken by purse seines. A considerable portion of the purse seine catch is transported to holding pens for fattening and later sale as sashimi grade fish (IATTC 2008).

Conservation Actions [top]

Conservation Actions: Mexico has quotas in place to limit the amount of fish that can be caught for fish farms. There is no longer any US catch for this species, and historically high catches for the U.S. are likely due to U.S. fishing in Mexican waters.
Citation: Collette, B., Acero, A., Boustany, A., Canales Ramirez, C., Cardenas, G., Carpenter, K.E., Chang, S.-K., Chiang, W., Di Natale, A., Die, D., Fox, W., Graves, J., Hinton, M., Juan Jorda, M., Minte Vera, C., Miyabe, N., Montano Cruz, R., Nelson, R., Restrepo, V., Schaefer, K., Schratwieser, J., Serra, R., Sun, C., Uozumi, Y. & Yanez, E. 2011. Thunnus orientalis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 17 April 2014.
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