Euthynnus affinis 

Scope: Persian Gulf
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Perciformes Scombridae

Scientific Name: Euthynnus affinis (Cantor, 1849)
Regional Assessments:
Common Name(s):
English Kawakawa, Black Skipjack, Bonito, Eastern Little Tuna, Mackerel Tuna, Oceanic Bonito
French Bonite, Bonite à Dos Rayé, Bonite D'Inde, Petit Thon, Thonine, Thonine Orientale
Spanish Bacoreta, Bacoreta Oriental, Bonito
Euthynnus yaito Kishinouye, 1915
Thynnus affinis Cantor, 1849
Wanderer wallisi Whitley, 1937

Assessment Information [top]

Red List Category & Criteria: Least Concern (Regional assessment) ver 3.1
Year Published: 2015
Date Assessed: 2013-11-03
Assessor(s): Collette, B.B., Smith-Vaniz, W.F., Hartmann, S., Alam, S., Alghawzi, Q., Abdulqader, E., Bishop, J. & Kaymaram, F.
Reviewer(s): Buchanan, J.
Facilitator/Compiler(s): Linardich, C. & Buchanan, J.
Euthynnus affinis is widespread throughout the Persian Gulf. It is an important commercial species with increasing regional landings. Euthynnus affinis is included as bycatch in the gill net fisheries for Scomberomorus commerson and Thunnus tonggol. However, it is not directly targeted by any fishery, but is considered fully exploited in the southern waters off of Iran. Overall, this not considered a major threat in all parts of the Persian Gulf. Euthynnus affinis is listed as a migratory species in Annex I of the 1982 Convention on the Law of the Sea. Oceanographic data suggests that a rescue effect through the Strait of Hormuz is negligible. Euthynnus affinis is listed as Least Concern, but it is recommended that the population requires monitoring.

Geographic Range [top]

Range Description:Euthynnus affinis occurs throughout the Persian Gulf (Collette 1984).
Countries occurrence:
Bahrain; Iran, Islamic Republic of; Iraq; Kuwait; Qatar; Saudi Arabia; United Arab Emirates
FAO Marine Fishing Areas:
Indian Ocean – western
Additional data:
Lower depth limit (metres):50
Range Map:170336-26

Population [top]


Euthynnus affinis is common throughout the Persian Gulf and is similar to Scomberomorus commerson, catch off of Iran is not declining in the gill net fishery (F. Kaymaram pers. comm. 2013). Off Saudi Arabia, E. affinis is captured as bycatch in the directed gill net fishery for S. commerson (Q. Alghawzi pers. comm. 2013).

Motlagh et al. (2010) estimated the total, fishing and natural mortality rates for Euthynnus affinis in the southern Iranian waters of the Gulf to be 2.37 year-1, 1.72 year-1, and 0.65 year-1, respectively. The exploitation rate of E. affinis was estimated to be 0.72 year-1. Estimates of the annual stock at the beginning of the year and annual average standing stock were estimated to be 7,924 and 2,994 tonnes, respectively. Motlagh et al. (2010) determined that the E. affinis stock in Hormozgan waters is severely overexploited, since fishing mortality (1.72 year-1) is substantially greater than the target (Fopt = 0.33 year-1) and limit (Flimit = 0.43 year-1) biological reference points. The fishing mortality rate was also greater than the maximum yield per recruit (1.6 year-1), which suggests that growth over fishing is occurring. Size at first capture was estimated to be 46.9 cm FL, which is smaller than the maximum yield per recruit recommended (61 cm FL). Motlagh et al. (2010) suggests that that an increase of the mesh size in nets be considered. 

Kaymaram and Darvishi (2012) estimated the total, fishing and natural mortality rates for Euthynnus affinis in the northern part of the Persian Gulf and Gulf of Oman to be 2.58 year-1, 1.82 year-1, and 0.76 year-1, respectively. The exploitation rate of E. affinis was estimated to be 0.7 year-1. Growth parameters K and Lwere estimated to be 0.67 year-1 and 95.06 cm, respectively. Growth performance index (ǿ) of E. affinis was estimated to be 8.7. Farhad and Darvishi (2012) determined that E. affinis was highly exploited in the northern Persian Gulf and Gulf of Oman during the course of their study period and concluded that it is necessary to impose fishing regulations on this species stock, which can be done so with gradual increase in mesh size of gill nets, through the restriction of fishing during certain seasons, or by declaring fish sanctuaries in certain areas, such as spawning grounds.

Hosseini et al. (2012) determined Euthynnus affinis occurred in 3.3% of the total bycatch collected in the cutlassfish trawl fishery in Hormozgan waters (off Iran).

Aggregate FAO RECOFI landings of Euthynnus affinis show an overall increasing trend with 1,994 tonnes in 1986 to 19,499 tonnes in 2011, with a peak of 21,285 tonnes collected in 2008 (FAO 2013).

Oceanographic data suggests that a rescue effect through the Strait of Hormuz is negligible.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Euthynnus affinis is pelagic and oceanodromous occurring in open waters, but it always remains close to the shoreline. It is found to 50 m depth. The young may enter bays and harbours. It forms multi-species schools by size with other scombrid species, comprising from 100 to over 5,000 individuals. It is a highly opportunistic predator feeding indiscriminately on small fishes, especially on clupeoids and atherinids (e.g., 78% by weight, 71% frequency in eastern Australia (Griffiths et al. 2009). It also feeds on squids, crustaceans and zooplankton (Collette 2001).
Yesaki and Arce (1994) and Muthias (1985) report the apparent length at 50% maturity for this species off India to be 43 cm. A study conducted in Taiwan found the age at first maturity to be two years (Chiou et al. 2004). Longevity has been estimated at six years (Landau 1965).

This species spawns extensively, both geographically and temporally, throughout its range (Schaefer 2001). Although spawning distributions of all three Euthynnus species have been reported to be restricted primarily to peripheral areas and around islands (Yoshida 1979, Nishikawa et al. 1985), spawning in the eastern tropical Pacific has been shown to be widely distributed from coastal to oceanic waters (Schaefer 1987).

Maximum Size is 100 cm fork length (FL), about 13.6 kg. The all-tackle game fish record is of a 13.15 kg fish caught off Isla Clarion, Revillagigedo Islands, Mexico, in the eastern Pacific outside the usual range of this Indo-West Pacific species (IGFA 2015).
Movement patterns:Full Migrant

Use and Trade [top]

Use and Trade: Euthynnus affinis is important in highly commercial fisheries and is generally marketed canned and frozen. It is utilized dried, salted, smoked (Collette 2001) and fresh. This species is also used in pet food for dogs and cats.

Threats [top]

Major Threat(s): Euthynnus affinis is an important commercial species of the Persian Gulf. Motlagh et al. (2010) determined that the Iranian stock of Euthynnus affinis was overexploited and being growth over-fished. Euthynnus affinis is also collected as bycatch (Hosseini et al. 2012, Q. Alghawzi pers. comm. 2013).

Conservation Actions [top]

Conservation Actions: There are no known species-specific conservation measures in place for Euthynnus affinis. However, there are several marine protected areas within its distribution, including the Jubail Marine Wildlife Sanctuary, where Euthynnus affinis has been recorded (Krupp and Muller 1994, Krupp and Almarri 1996). Euthynnus affinis is listed as a highly migratory species in Annex I of the 1982 Convention on the Law of the Sea (Garcia 1994). More information is needed on this species population and the impact of fisheries, especially as it seems that many catches are not being reported.

Citation: Collette, B.B., Smith-Vaniz, W.F., Hartmann, S., Alam, S., Alghawzi, Q., Abdulqader, E., Bishop, J. & Kaymaram, F. 2015. Euthynnus affinis. The IUCN Red List of Threatened Species 2015: e.T170336A57236612. . Downloaded on 20 September 2018.
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