Habitat and Biology
Climatic zone: Temperate; Tropical.
Information on the habitat and biology of tunas and tuna like species is further described in the factsheet on the Biological characteristics of tunas and tuna-like species
and in Goujon
and Majkowski (2010). Global aspects of tuna resources, fishing, fisheries management,
processing and trade can be found in Allen (2010), Joseph (1998, 2000, 2003), Miyake,
Miyabe and Nakano (2004) and Miyake et. al. (2010). Information references at regional
scale are given in the respective sections on resource status.
Jurisdictional distribution: Highly migratory
The 1982 UNCLOS classifies the principal market tunas, billfishes, blackfin tuna,
bullet and frigate tuna, little tunny and kawakawa as highly migratory. This is despite
little tunny and kawakawa being mostly confined to the continental shelf and upper
slope. Black skipjack is not classified as highly migratory, but it is probably more
oceanic than little tunny and kawakawa.
Considered a single stock: No
The suborder Scombroidei is usually referred to as tuna and tuna-like species (Klawe,
1977; Collette and Nauen, 1983; Nakamura, 1985). It is composed of tunas (sometimes
referred to as true tunas), billfishes and other tuna-like species. They include some of
the largest and fastest fishes in the sea. The tunas are classified into 5 genera (Thunnus
) with 15 species all together.
The most economically important tuna species on the global scale are referred to as
principal market tunas. From the genus Thunnus
, they include albacore (T. alalunga
Atlantic bluefin tuna (T. thynnus
), bigeye tuna (T. obesus
), Pacific bluefin tuna
), southern bluefin tuna (T. maccoyii
) and yellowfin tuna (T. albacares
Skipjack tuna (Katsuwonus pelamis
) is the seventh principal market tuna species. They
are subject to intensive international trade for canning and sashimi (raw fish regarded as
a delicacy in Japan and, increasingly, in many other countries).
The efficient physiology of principal market tunas allows them to retain or dissipate
heat as required for peak biological performance and efficiency. They are all oceanic
(Figure C1.1), capable of long migrations or movements, but not necessarily all species
re-distribute or mix well within the areas of their stocks’ distribution. Most species
constitute one or two stocks in each ocean, although the albacore in the Atlantic consists
of three stocks (including that in the Mediterranean Sea). The exceptions are Atlantic
and Pacific bluefins, which occur only in their eponymous oceans. Southern bluefin
constitute a single stock extending in the Atlantic, Indian and Pacific Oceans.
The tunas other than the principal market species are more neritic (living in water
masses over the continental shelf). They include longtail tuna, blackfin tuna (T. atlanticus
black skipjack (E. lineatus
), kawakawa (E. affinis
), little tunny (E. alleteratus
tuna (A. rochei
) and frigate tuna (A. thazard
The billfishes (Istiophoridae) are composed of marlins (Makaira
spp.), spearfish (Tetrapturus
spp.) and swordfish (Xiphias gladius
species in the genus). With the exception of two species (Mediterranean and roundscale
spearfish), all billfishes have very wide geographical distributions, but not all species
occur in all oceans. Billfishes are mostly caught by longlines as bycatch. The exceptions
are swordfish, which are targeted in certain regions with longlines and harpoons.
Billfishes are also taken in sport fisheries, where they are greatly valued. They are all
considered excellent eating.
Other important tuna-like species include slender tuna (Allothunnus fallai
kingfish (Gasterochisma melampus
), wahoo (Acanthocybium solandri
), Spanish and king mackerels, seerfish and sierra
spp.). They and other tuna-like species are all the object of fishing.
They have a significant fishery potential, especially for developing countries where
mostly artisanal and recreational fisheries are now catching them. Slender tuna and
butterfly kingfish (with a circumpolar distribution in the Southern Ocean) are now
caught mostly as bycatch of the Japanese longline fishery targeting southern bluefin
|Figure C1.1 Distribution of principal market tunas and fishing areas |
Information on fishery are available at the following link: World oceans Global Tuna fisheries
Biological State and Trend
PRINCIPAL MARKET TUNAS
The following classification of the status of stocks is used throughout this document.
- U Non-fully exploited.
- F Fully exploited.
- O Overexploited.
For Further clarifications on the criteria for the classification of fish stock status, see the Source Report (Appendix - Assessment methodology, Table 1)
A summary on the status of various stocks of tuna and tuna-like species is given in
Table D19. It was obtained by interpreting results of stock assessments according to the
classification procedure adopted by FAO in this review. Those assessments available
at the time of preparation of this review (end of March 2011) were taken mostly from
Web pages of:
Commission for the Conservation of Southern Bluefin Tuna (CCSBT );
Inter-American Tropical Tuna Commission (IATTC ) for the
International Commission for the Conservation of Atlantic Tunas (ICCAT );
Indian Ocean Tuna Commission (IOTC );
Western Central Pacific Fishery Commission (WCPFC ).
The knowledge and data on the principal market tunas are generally much better than
those for other species of tuna and tuna-like species. They have been studied for many
years and more research effort is devoted to them. However, even for these species,
significant uncertainties exist in the basic biological knowledge and data. For example,
relatively recent research indicates that the life span of southern bluefin tuna, one of
the best studied tuna, may be considerably longer than previously believed. Moreover,
for this species, as compared with trade statistics, the catches were substantially
under reported for a number of years. For Atlantic bluefin tuna, another well-studied
species, officially reported catches might be significantly smaller in the past than those
actually taken. This conclusion is based on information from a trade-based statistical
programme introduced by ICCAT (Miyake, 1998) as well as from capacity estimates
(ICCAT, 2009). When considering the information on the stock status, uncertainties in
stock assessment need to be taken into account.
Most tuna stocks are fully exploited, some are overexploited. Generally, some
temperate tuna species (i.e. Atlantic and southern bluefins [most desired for sashimi])
are much more overexploited (depleted) than any of the tropical tuna species. For the
Pacific bluefin (also used for sushimi), the yield-per-recruit could be increased if the
number of small bluefin caught by trolling and purse seining can be reduced.
The stocks of albacore (temperate species) used mostly for canning are not fully
exploited in the South Pacific but they are fully exploited in the Indian Ocean and the
South Atlantic and overexploited in the North Atlantic and the North Pacific. The
status of albacore in the Mediterranean Sea is unknown.
Generally, most tropical principal market tunas have reacted well to exploitation
owing to their very high reproductive potential, wide geographical distribution,
opportunistic behaviour and other population dynamics characteristics that make them
highly productive. With proper management, they are capable of sustaining high yields.
There may still be potential for increasing catches of skipjack in the western and
central Pacific with lower potential in the other oceans. However, skipjack are caught
together with tuna species that are fully exploited or overexploited. Therefore, until
more selective fishing methods are developed, it is not desirable to increase the catches
Most other stocks of tropical tunas have become fully exploited and a few are
overexploited. Generally, a possibility of further deterioration in the status of tropical
tunas should not be underestimated. Concerns are increasing over the exploitation of
bigeye in all oceans. This is another species that is highly desired for sashimi and has a
shorter life span than bluefin. In addition to possibly causing overfishing in the future,
the increasing purse seine catches of small bigeye may negatively affect the yield per
The status of many tuna and tuna-like species other than the principal tunas is highly
uncertain or simply unknown. Therefore, the intensification of their exploitation
raises concerns. Significant uncertainties in the status of many billfishes represent a
serious conservation problem. Some stocks are overexploited in the Atlantic and
the Pacific, while their status is mainly unknown in the Indian Ocean. Because of
commercial exploitation, there is more known about swordfish than other billfishes. In
the Mediterranean Sea, the swordfish stock seems to be overexploited, but the overall
situation in the remainder of the Atlantic and Pacific is more optimistic. However, in
the Indian Ocean, there are concerns about the intensification of swordfish fishing
owing to the risk of potential local overexploitation.
Table D19: State of exploitation and annual nominal catches of tuna and tuna-like species in all Oceans, 1950–2009.
Source of information
Marine and Inland Fisheries Service, Fisheries and Aquaculture Resources Use and Conservation Division. FAO Fisheries and Aquaculture Department “Review of the state of world marine fishery resources”
FAO FISHERIES AND AQUACULTURE TECHNICAL PAPER.
No. 569. Rome, FAO. 2011.
The bibliographic references are available through the hyperlink displayed in "Source of Information".ACKNOWLEDGEMENTS
The authors are grateful to Dr Peter Miyake and his colleagues for their help with
the provision of information for the preparation of the section ob Fisheries and Table
C1.1. They also appreciate the assistance of the Secretariats and tuna scientists of FFA,
t-RFMOs and SPC with obtaining information for this review and their cooperation and
collaboration with FAO. Drs Robin Allen and Victor Restrepo have kindly provided
helpful suggestions for improving an earlier version of this review.