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Tuna and tuna-like species are very important economically and a significant source of food, with the so-called principal market tuna species - skipjack, yellowfin, bigeye, albacore, Atlantic bluefin, Pacific bluefin (those two species previously considered belonging to the same species referred as northern bluefin) and southern bluefin tuna - being the most significant in terms of catch weight and trade. These pages are a collection of Fact Sheets providing detailed information on tuna and tuna-like species.

 

Table of Contents

 

Taxonomy and classification

[ Family: Scombridae ] :  Scombrids

[ Family: Istiophoridae  Family: Xiphiidae ] :  Billfishes

Upper systematics of tunas and tuna-like species
Scombrids and billfishes belong to the suborder of the Scombroidei which position is shown below:

Phylum : Chordata
  └─ Subphylum Vertebrata
           └─ Superclass Gnathostomata
                    └─ Class Osteichthyes
                              └─ Subclass Actinopterygii
                                        └─ Infraclass Teleostei
                                                  └─ Superorder Acanthopterygii
                                                            └─ Order Perciformes
                                                                      ├─ Suborder Scombroidei
                                                                       |        └─ Family Scombridae
                                                                      └─ Suborder Xiphioidei 
                                                                                ├─ Family Istiophoridae
                                                                                └─ Family Xiphiidae

Scombrids

The scombrids belong to the family of the Scombridae which is comprised of 15 genera and 51 species. These species are assigned to 2 sub-families:
the Gasterochismatinae with only 1 species and the Scombrinae divided into 4 tribes:
the mackerels (Scombrini)
the seerfishes or Spanish mackerels (Scomberomorini)
the bonitos (Sardini)
the tunas (Thunnini)

The tribe Thunnini (tunas for ichthylogists) contains 14 species in 4 genera:
Thunnus (8 species)
Katsuwonus (1 species)
Euthynnus (3 species)
Auxis (2 species)

However, in several languages, the word "tuna" is used for members of both the tribe Thunnini and the tribe Sardini (8 species).

Origin of the word "tuna"

The word "tuna" is applied to certain members of the family Scombridae, a group of marine fishes including tunas, bonitos, mackerels, seerfishes and the butterfly kingfish. However, for ichthyologists, tuna refers to any of the 14 species of the tribe Thunnini within the family Scombridae (Klawe, 1977). The word "tuna" seems to have come into use in the second half of the last century, but it is not clear why it replaced the older name "tunny". It may have been brought to southern California by fishermen originated from Europe, either from the Dalmatian coast of the former Yugoslavia or from the Iberian Peninsula (Klawe, 1976). The European names of tuna (thon in French, atún in Spanish, tonno in Italian, …) find their origin in the latin name thunnus itself issued from the Greek name θύννος, (thýnnos) derived from the verb “thynno” which means “to rush”.

Principal market tuna species

Among the 14 species of tuna, skipjack, yellowfin, bigeye and albacore constitute more than 80% of the world catch since 1950. Three other species, Atlantic bluefin, Pacific bluefin and southern bluefin tuna, are also commercially important due to the high prices paid for them. These above-mentioned species are often referred as "principal market tuna species".



Billfishes

The billfishes include 2 families: the Xiphiidae with one species, the swordfish (Xiphias gladius) and the Istiophoridae with 12 species within 4 genera.

The systematics of billfishes was recently revised by Orell et al. (2006) and Collette et al. (2006) using molecular analyses of nuclear DNA and mitochondrial DNA cytochrome b, leading to the distinction of billfishes from scombroids in a separate suborder, Xiphioidei and to the revision of billfish genera. Moreover, the lack of justification for separating the Atlantic sailfish (Istiophorus albicans) from the Indo-Pacific sailfish (I. platypterus) leads the author to gather them both under the latter genus. Similarily, Atlantic blue marlin (Makaira nigricans) and Indo-Pacific blue marlin (M. mazara) are regrouped in the single genus Makaira nigricans.



Scientific and common names in English, French and Spanish of tunas and tuna-like species

   Tunas and bonitos
Scientific name
Common names, acknowleged by FAO, in: English  French  Spanish;     3-alpha code

Thunnini
Thunnus alalunga
Thunnus albacares
Thunnus atlanticus
Thunnus maccoyii
Thunnus obesus
Thunnus thynnus
Thunnus orientalis
Thunnus tonggol
Katsuwonus pelamis
Euthynnus affinis
Euthynnus alleteratus
Euthynnus lineatus
Auxis rochei
Auxis thazard

Tunas
Albacore
Yellowfin tuna
Blackfin tuna
Southern bluefin tuna
Bigeye tuna
Atlantic bluefin tuna
Pacific bluefin tuna
Longtail tuna
Skipjack
Kawakawa
Little tunny
Black skipjack
Bullet tuna
Frigate tuna

Thons
Germon
Albacore
Thon à nageoires noires
Thon rouge du Sud
Thon obèse
Thon rouge de l’Atlantique
Thon rouge du Pacifique
Thon mignon
Listao
Thonine orientale
Thonine commune
Thonine noire
Bonitou
Auxide
Atún
Atún blanco
Rabil
Atún aleta negra
Atún del Sur
Patudo
Atún rojo del Atlantico
Atún aleta azul del Pacifico
Atún tongol
Listado
Bacoreta oriental
Bacoreta
Barrilete negro
Melvera
Melva
 
ALB
YFT
BLF
SBF
BET
BFT
PBF
LOT
SKJ
KAW
LTA
BKJ
BLT
FRI
Sardini
Allothunnus fallai
Cybiosarda elegans
Gymnosarda unicolor
Orcynopsis unicolor
Sarda australis
Sarda chiliensis
Sarda orientalis
Sarda sarda

Bonitos
Slender tuna
Leaping bonito
Dogtooth tuna
Plain bonito
Australian bonito
Eastern Pacific bonito
Indo-Pacific bonito
Atlantic bonito
Bonites
Thon élégant
Bonite à dos tacheté
Bonite à gros yeux
Palomette
Bonite bagnard
Bonite du Pac. oriental
Bonite orientale
Bonite à dos rayé
Bonitos
Atún lanzón
Bonito saltador
Tasarte ojón
Tasarte
Bonito austral
Bonito del Pac. oriental
Bonito mono
Bonito atlántico
 
SLT
LEB
DOT
BOP
BAU
BEP
BIP
BON


    Seerfishes and mackerels
Scientific name
Common names, acknowleged by FAO, in: English French  Spanish;  3-alpha code

Grammatorcynus bicarinatus
Grammatorcynus bilineatus

Shark mackerel
Double-lined mackerel
Thazard requin
Thazard-kusara
Carite cazón
Carite cazón pintado
SHM
DBM
Scomberomorini
Acanthocybium solandri
Scomberomorus brasiliensis
Scomberomorus cavalla
Scomberomorus commerson
Scomberomorus concolor
Scomberomorus guttatus
Scomberomorus koreanus
Scomberomorus lineolatus
Scomberomorus maculatus
Scomberomorus multiradius
Scomberomorus munroi
Scomberomorus niphonius
Scomberomorus plurilineatus
Scomberomorus queenslandicus
Scomberomorus regalis
Scomberomorus semifasciatus
Scomberomorus sierra
Scomberomorus sinensis
Scomberomorus tritor

Seerfishes
Wahoo
Serra Spanish mackerel
King mackerel
Narrow-barred king mack.
Monterey Spanish mackerel
Indo-Pacific king mackerel
Korean seerfish
Streaked seerfish
Atlantic Spanish mackerel
Papuan seerfish
Australian spotted mackerel
Japanese Spanish mackerel
Kanadi kingfish
Queensland school mackerel
Cero
Broad-barred king mackerel
Pacific sierra
Chinese seerfish
West African Spanish mackerel
Thazards
Thazard-bâtard
Thazard serra
Thazard barre
Thazard rayé
Thazard Monterey
Thazard ponctué
Thazard coréen
Thazard cirrus
Thazard atlantique
Thazard papou
Thazard australien
Thazard oriental
Thazard Kanadi
Thazard de Queensland
Thazard franc
Thazard tigre
Thazard sierra
Thazard nébuleux
Thazard blanc
Carites
Peto
Serra
Carite lucio
Carite estriado
Carite de Monterey
Carite del Indo-Pacifico
Carite coreano
Carite rayado
Carite atlántico
Carite papuense
Carite australiano
Carite oriental
Carite canadí
Carite de Queensland
Carite chinigua
Carite tigre
Carite sierra
Carite indochino
Carite lusitánico
 
WAH
BRS
KGM
COM
MOS
GUT
KOS
STS
SSM
PAP
ASM
NPH
KAK
QUM
CER
BBM
SIE
CHY
MAW
Scombrini
Rastrelliger brachysoma
Rastrelliger faughni
Rastrelliger kanagurta
Scomber australasicus
Scomber colias
Scomber japonicus
Scomber scombrus

Mackerel
Short mackerel
Island mackerel
Indian mackerel
Spotted chub mackerel
Atlantic chub mackerel
Indo-Pacific Chub mackerel
Atlantic mackerel
Maquereaux
Maquereau trapu
Maquereau des îles
Maquereau des Indes
Maquereau tacheté
Maquereau espagnol de l’Atlantico
Maquereau espagnol indo-Pacífico
Maquereau commun
Caballa
Caballa rechoncha
Caballa isleña
Caballa de la India
Caballa pintoja
Estorino del Atlántico
Estorino del Indo-Pacífico
Caballa del Atlántico
 
RAB
RAF
RAG
MAA
MAS
MAS
MAC
Gasterochismatinae
Gasterochisma melampus


Butterfly kingfish

Thon papillon

Atún chauchera

BUK


    Billfishes
Scientific name
Common names, acknowleged by FAO, in: English  French  Spanish;         3-alpha code

Xiphias gladius
Istiophorus albicans
Istiophorus platypterus
Istiompax indica
Makaira mazara
Makaira nigricans
Kajikia albida
Kajikia audax
Tetrapterus angustirostris
Tetrapterus audax
Tetrapterus belone
Tetrapterus georgei
Tetrapterus pfluegeri

Swordfish
Sailfish
Indo-Pacific sailfish
Black marlin
Indo-Pacific blue marlin
Blue marlin
Atlantic white marlin
Striped marlin
Shortbill spearfish
Striped marlin
Mediterranean spearfish
Roundscale spearfish
Longbill spearfish
Espadon
Voilier de l'Atantique
Voilier de l'Indo-Pacifique
Makaire noir
Makaire bleu de l'Indo-Pacifique
Makaire bleu de l'Atlantique
Makaire blanc de l'Atlantique
Marlin rayé
Makaire à rostre court
Marlin rayé
Marlin de la Méditerranée
Makaire épée
Makaire bécune
Pez espada
Pez vela del Atlántico
Pez vela del Indo-Pacífico
Aguja negra
Aguja azul del Indo-Pacífico
Aguja azul del Atlántico
Aguja blanca del Atlántico
Marlín rayado
Marlín trompa corta
Marlín rayado
Marlín del Mediterráneo
Marlín peto
Aguja picuda
SWO
SAI
SFA
BLM
BLZ
BUM
WHM
SSP
MLS
MSP
RSP
SPF


Fossil records
The first fossil records of Scombridae are dated from the beginning of the lower Eocene epoch (60-40 million years ago) during the lower Tertiary period. As for the Istiophoridae, the oldest fossils are dated from the upper Cretaceous epoch (70-90 million years ago) during the Secondary period. For the Xiphiidae, the oldest fossil records are dated from the Paleocene epoch of the lower Tertiary period, i.e. 57-65 million years ago (Berg, 1958).

 

Morphological characteristics

Morphology of larvae

It is often difficult or impossible to identify larvae and, in some cases, early juveniles by anatomical characteristics or colour patterns. Biochemical or genetic methods can be used to distinguished the larvae of the various species (Elliott and Ward, 1995, Chow et al., 2003). Diagnostic keys are available for larvae between 3 and 12 mm standard length. Larvae smaller than 3 mm are virtually indistinguishable (Nishikawa and Rimmer, 1987).

Morphology of juveniles and adults

Characteristics common to both scombrids and billfishes

Both scombrids and billfishes have two distinct dorsal fins, generally separated, the first one supported by spines and the second only by soft rays. The pelvic fins are inserted below the base of the pectoral fins. The caudal fin is deeply notched.

Tuna and tuna-like fins

All scombrids and billfishes except swordfish have a pair of caudal keels on the middle of the caudal peduncle at the base of the caudal fin. The swordfish has only a large median caudal keel. The more advanced members of the Scombridae family also have a large median keel anterior to the pair of caudal keels. The bodies of all the Scombroidei are robust, elongate and streamlined. The first dorsal and first anal fins of all scombrids and billfishes, except swordfish, can fold down into grooves and the pectoral and pelvic fins into depressions when the fish is swimming rapidly.

Grooves

The scombrids and billfishes, all have four gill arches on each side. The gill filaments are ossified as "Gill rays".

Scombrids

The scombrids are characterised by the presence of at least four finlets behind the dorsal and the anal fins. The pelvic fins are smaller than the pectoral fins or of equal size. Except for the primitive butterfly kingfish, which body is covered by large cycloid scales, the body of all the scombrids is naked or covered with small to moderate-sized scales. The bonitos (Sardini) are intermediate between the seerfishes and the tunas. As is the case for the tunas, they have a well-developed corselet of scales, but they lack the two longitudinal ridges on the upper surface of the tongue. The most primitive Scombrinae are the mackerels (Scombrini), the seerfishes (Scomberomorini) and the two-line mackerels (Grammatorcynus spp.). The mackerels have only two caudal keels, whereas the seerfishes and the two-line mackerels have a larger median keel in front of the pair of keels.

The tunas are the most highly evolved of the scombrids. They are unique among bony fish in having heat exchanger systems that allow them to regulate their body temperature, as can birds and mammals (see the thermoregulation).



Billfishes

The billfishes are characterised by their rostrum, an extension of the upper jaw, which extends much beyond the lower jaw.

Billfishes rostrum
Billfishes rostrum


The rostrum has a flat, sword-like cross section for the swordfish and a rounded, spear-like cross section for the Istiophoridae.
The swordfish is also characterised by the absence of pelvic fins and scales. Its dorsal fins are well separated, and has only one large median caudal keel. The Istiophoridae have long, rigid, tapering pelvic fins. Their bodies are covered with small, elongate, bony scales. Their first dorsal fin has a long base and terminates close to the origin of the second dorsal fin.



Geographical distribution

Tropical and temperate tunas

Because of different distributions due to their specific thermal tolerances and because of exploitation by different fisheries, a distinction is made between tropical and temperate tunas. Tropical tunas are found in waters with temperatures greater than 18° C (although they can dive in colder waters) whereas temperate tuna are found in waters as cold as 10°C, but can also be found in tropical waters (Brill, 1994).

   Tropical tunas: skipjack and yellowfin
   Intermediate tunas: bigeye
   Temperate tunas: albacore, Pacific bluefin, Atlantic bluefin and southern bluefin

 

Tropical and temperate tunas Tropical and temperate tunas
Tropical tunas Tropical tunas  Temperate tunas Temperate tunas

Scombrids

Tunas prefer oceanic waters, and 3 of the 8 species of Thunnus are found worldwide except in the Arctic Ocean. Most bonitos and little tunas (Euthynnus spp.) are primarily neretic, ie coastal fishes, but the distribution of individual species is often widespread. The frigate and bullet tunas (Auxis spp.) are probably both oceanic and coastal (Olson and Boggs, 1986). The slender tuna and the butterfly kingfish have circum-global distributions in the Southern Ocean. Most mackerels and seerfishes have restricted ranges of distribution. Exceptions are the Spanish mackerel and the wahoo which are found worldwide.


Oceanic and neritic tunas

Oceanic and neritic tunas
Oceanic tunas Oceanic tunas  Neritic tunas Neritic tunas

Billfishes

Billfishes are widely distributed, at least, throughout the oceans in which they occur. The exception are the Mediterranean spearfish, which occurs only in the Mediterranean Sea, and perhaps the roundscale spearfish, which occur in the northeastern Atlantic Ocean around the Canary and Madeira Islands and in the western Mediterranean Sea. However, only the swordfish is cosmopolitan. All other Istiophoridae are being confined to the Atlantic Ocean or to the Indian and Pacific Oceans.

Occurrence of the tuna, bonito and billfish species in the different oceans

Common names Scientific name Areas of occurrence
   Tunas and bonitos 
Skipjack  Katsuwonus pelamis  worldwide 
Yellowfin tuna  Thunnus albacares  worldwide 
Bigeye tuna  Thunnus obesus  worldwide 
Albacore tuna  Thunnus alalunga  worldwide 
Atlantic bluefin tuna  Thunnus thynnus  Atlantic Ocean 
Pacific bluefin tuna  Thunnus orientalis  Pacific Ocean 
Southern bluefin tuna  Thunnus maccoyii  southern parts of Atlantic, Indian and Pacific Ocean 
Longtail tuna  Thunnus tonggol  Indian Ocean, western Pacific Ocean 
Blackfin tuna  Thunnus atlanticus  western Atlantic Ocean 
Kawakawa  Euthynnus affinis  Indian, western and central Pacific Oceans 
Black skipjack  Euthynnus lineatus  eastern Pacific Ocean 
Little tunny  Euthynnus alleteratus  Atlantic Ocean 
Bullet tuna  Auxis rochei  worldwide 
Frigate tuna  Auxis thazard  Indian and Pacific Oceans 
Slender tuna  Allothunnus fallai  Southern Ocean 
   Billfishes 
Swordfish  Xiphias gladius  worldwide 
Atlantic sailfish  Istiophorus albicans  Atlantic Ocean 
Indo-Pacific sailfish  Istiophorus platypterus  Indian and Pacific Oceans 
Black marlin  Makaira indica  Indian and Pacific Oceans 
Indo-Pacific blue marlin  Makaira mazara  Indian and Pacific Oceans 
Atlantic blue marlin  Makaira nigricans  Atlantic Ocean 
Atlantic white marlin  Tetrapterus albidus  Indian and Pacific Oceans 
Striped marlin  Tetrapterus audax  Indian and Pacific Oceans 

 

Habitat and biology

Ecological niche

Tunas are pelagic marine fish, spending their entire lives relatively near the surface of tropical, subtropical and temperate oceans and seas. Scombrids and billfishes live primarily in the water layers above the thermocline, but are able to dive to depth of several hundred meters (see the Vertical distribution section). Tuna species attaining only small sizes and juveniles of those attaining large sizes are encountered in epipelagic waters (from the surface to the thermocline) whereas large tunas tend to be mesopelagic and are found also in deeper and cooler waters.

   Epipelagic tunas: skipjack and bonitos, juveniles of large tunas, billfishes
   Mesopelagic tunas (adults): albacore, bigeye and bluefin
   Tunas that are found at both depth ranges: yellowfin, swordfish


Some tunas are found in both offshore and coastal waters and others entirely, or almost entirely, in coastal waters.

   Mid-ocean species: yellowfin and bigeye, swordfish
   Coastal species: Thunnus tonggol, other bonitos than Auxis spp., little tunas (Euthynnus spp.)
   Species found in both waters: skipjack, albacore, Pacific bluefin, Atlantic bluefin and southern bluefin, Auxis spp.

Seerfishes are generally restricted to coastal waters and enter estuaries to feed. One species, the Chinese seerfish moves long distances in freshwater up the Mekong River in China.

Distribution of tunas and tuna-like in the water Distribution of tunas and tuna-like in the water

Tuna and their environment

Important environmental parameters for tuna are the sea surface temperature, the quantity of dissolved oxygen in the water and the salinity. Lower thermal boundaries vary between 10°C for temperate tunas and 18°C for tropical tunas (see above; Brill, 1994). The minimum oxygen requirement is estimated between 2 to 2.7 ml/l for principal market tuna species except for bigeye tuna which can tolerate oxygen concentrations as low as 0.6 ml/l (Sharp, 1978 ; Lowe, 2000). Most tunas tend to concentrate along thermal discontinuities such as oceanic fronts (Sund, 1981).

Vertical distribution constraints and diving behavior

The vertical distribution of most species of tunas is influenced by the thermal and oxygen structure of the water column. Tuna species attaining only small sizes and juveniles of those attaining large sizes tend to live near the surface, whereas adults of large species are found in deeper waters. The use of deep longlines showed that bigeye can be found at depths as great as 300 m (Suzuki et al., 1977). Albacore are also caught under FADs at depths to about 200 m (Bard et al., 1998). Acoustic telemetry has shown that billfishes are found near to the surface during the day, descending more frequently to greater depths at night (Block et al., 1992a).
Yellowfin, Bigeye, Bluefin and Swordfish show deeper dives than other species of tuna and billfish (Fromentin & Fonteneau, 2001; Sund, Blackburn & Williams, 1981):
- Yellowfin tuna has been observed to dive at more than 1100 m (record of 1200 m, L. Dagorn et al., 2006).
- Bigeye tuna are capable of diving to depths of more than 1200 m (record of 1800 m, Schaefer, Comm. pers.).
- Atlantic bluefin tuna are able to dive to depths in excess of 1000 m, encountering an exceptionally wide range of temperatures (Block et al., 2005).
- Swordfish make large vertical excursions, coming close to the surface at night and diving as deep as 600 m during the day ((Carey and Robison, 1981); Sedberry and Loefer, 2001), even 900 m (Takahashi et al., 2003).
Other tunas show lesser diving capabilities, as, for example, Euthynnus affinis which have been observed at 400 m depth (Lee, 1982).

Schooling behavior

Tunas use schooling to their advantage when they forage. Some tunas form parabolic-shaped schools to encircle their prey. Most tunas school according to size. Juveniles of tunas attaining large sizes are, therefore, often associated with tunas attaining only small sizes, such as skipjack or bonito. Schools of large adults consist of a few scattered individuals. Schooling offers protection for juvenile tunas by confusing predators and reducing the likelihood that any single fish will become a victim to a predator. Atlantic bluefin tuna can form giant schools spread over several nautical miles when migrating into the Mediterranean Sea to spawn during the summer. As is the case with the other fishes, the structure of tuna schools is maintained by the lateral line. Schools can gathered over 5000 individuals.

Migration and other movements

All tunas and tuna-like fishes move constantly to search for food and to keep water passing over their gills. Migrations are seasonal movements, often over long distances, for the purpose of feeding or reproduction. Temperate tunas, i.e. albacore, Atlantic bluefin and Pacific bluefin, migrate long distances between temperate waters, where they feed, and tropical waters, where they spawn without moving among different oceans. Southern bluefin tuna migrates among the southern parts of Atlantic, Indian and Pacific Oceans. Although, the distribution of the three species of bluefin is quite extended, their spawning is restricted to relative small areas of tropical waters. Tropical tunas, i.e. skipjack and yellowfin, are less migratory in terms of long-distance directional movements, although several tagged yellowfin released in the western Atlantic have been recaptured in the eastern Atlantic. Bigeye have some of the characteristics of both temperate and tropical tunas. They apparently do not make trans-oceanic migrations, but like the temperate tunas, they migrate back and forth between feeding grounds in temperate waters and their spawning grounds in tropical waters. When they are not making directional migration, tunas move nearly all the time in search of areas where the food is most abundant. Fishermen are sometimes able to predict on the basis of oceanic conditions where the fish are likely to appear and then, they can transfer their operations to those areas. Less is known of the movements of billfishes, but apparently, they make seasonal migrations between temperate waters, where they feed, and tropical waters, where they spawn. For instance, blue marlin display extensive trans-equatorial and inter-oceanic movements from the Atlantic into the Indian Ocean (Ortiz et al., 2003).

Swimming

Tunas are excellent swimmers, and their bodies are designed for high performance at both sustainable and burst swimming speeds (Dickson, 1995). Tunas must swim constantly to satisfy their oxygen requirements and consequently stay alive. The direction of movements of some species, such as skipjack, seem to be dictated solely by the availability of food. The movement of other species, such as the three species of bluefin, seem to be influenced by both the distribution of food and the need to return to their ancestral spawning grounds at the proper time. Tunas can move up to 15 km per night in order to forage on organisms that swim upward from deeper waters at that time.


Tunas have higher cruising speeds than do other active fishes, including other scombroids (Beamish, 1978; Block et al., 1992b). The morphology of the body and caudal fin of tunas is optimal for prolonged, high-speed swimming. Similar body designs are found also in cetaceans, carangids, certain sharks and even the extinct reptilian ichthyosaurs. Webb (1984) lists the following morphological adaptations:
a lunate tail of large span, but relatively small chord to maximize the thrust
a narrow caudal peduncle to provide for locally-large amplitude displacements and to control the angle of attack
a large anterior body depth and mass to reduce recoil energy losses
a relatively-rigid streamlined body to both minimize the drag and maximize the thrust

Long-range swimming

The net distances travelled by tunas and billfishes (shortest distances between the locations of release and recapture) exceed those of any other fish, as shown by the following records obtained from tagging studies (from Joseph et al., 1988 for tunas and Orbesen et al., 2008 for billfishes):

10,790 km for a Pacific bluefin tuna (from southeast of Japan to off Baja California)
10,680 km for a black marlin (from off Baja California to Norfolk Island in the South Pacific Ocean)
9,500 km for a skipjack tuna (from off Baja California to the Marshall Islands)
8,500 km for an albacore tuna (from off California to off Japan)
7,700 km for an Atlantic bluefin tuna (accross the Atlantic Ocean)
15,744 km for a blue marlin (accross the Atlantic Ocean)
14,556 km for a black marlin (across the Pacific Ocean, comm.. pers.)
6,523 km for a white marlin (across the Atlantic Ocean)
3,845 km for a sailfish (across the Atlantic Ocean)


In addition, net movements of more than 5,000 km have been recorded for yellowfin tuna, bigeye tuna, blue marlin, striped marlin and sailfish.

Short-range, fast swimming

Scombrids and billfishes are adapted to fast swimming. The champions are, of course, the most highly evolved scombrids, the bonitos (Sardini) and the tuna (Thunnini) and the billfishes. They are able to exhibit startling bursts of speed, often exceeding one body length per second.The record (for all bony fishes) belongs to the black marlin (Makaira indica), which has been clocked at over 130 km/h.

Estimated maximun swimming speed of some tunas and billfishes

Species Sustained in m/s Burst in m/s
   Scombrids 
Thunnus albacares(1)  0.64  20.46 
Thunnus obesus (1)  0.6 
Thunnus thynnus (1)  3.49 
Katsuwonus pelamis (1)  0.84  9.41 
Euthynnus affinis (1)  0.76 
Auxis rochei (1)  0.68 
Sarda chiliensis (1)  0.88  3.70 
Sarda sarda (1)  0.35  1.2 
Acanthocybium solandri (1)  0.4  21.23 
Scomber japonicus (1)  0.92  2.25 
Scomber scombrus (2)  0.98  5.4  
   Billfishes 
Tetrapterus audax (3)  1.8 
Makaira indica (3)  36.1 
Makaira nigricans (3)  2.25 
Xiphias gladius (2)  24.86 

References
(1): Magnuson (1978)
(2): Wardle and He (1988)
(3): Block et al. (1992b)

Physiological aspects of swimming

In order to swim at high speeds for long periods, tunas are capable of taking in and utilizing large amounts of oxygen.

In contrast to other fishes that contract their jaws and opercular muscles to pump water over their gills, tunas and billfishes (and some species of sharks) ram ventilate, that is they swim through the water with their mouths open, which forces water over their gills. This is an efficient way to get a large amount of water flowing through the gills at a low energetic cost, but it has an important drawback: tunas cannot stop swimming, or they will suffocate! They must swim at a speed of at least 0.65 m/s to provide sufficient flow of water over their gills.

The amount of gill surface of tunas is up to 30 times those of other fish, and for some tunas the absorptive surface approaches those of the lungs of mammals of comparable weight (Joseph et al., 1988). This large surface enables the tunas to extract about half of the oxygen present in the water flowing over their gills.

To transfer oxygen from the gills to the other tissues, tunas have hearts that are about 10 times the size, relative to the weight of the entire body, of those of other fish. The blood pressure of tunas is about three times those of other fishes, and their hearts pump blood at a rate about three times those of other fish. The blood of tuna has a hematocrit of 40%, a value usually associated with diving mammals.

Scombrids and billfishes, like most fish, have two types of muscle, white and red. The white muscles function during short bursts of activity, while the red muscles, which have a relatively large mass, allow the fish to swim at high speeds (up to 45 km/h) for long periods without fatigue, as demonstrated by tagging studies with conventional and sonic tags (Joseph et al., 1988 ; Bushnell and Holland, 1997).

The proportion of red muscle is much greater for tunas than for other fish (Dickson, 1995) and their white muscles are capable of working in both aerobic and anaerobic conditions. Therefore, the increase in swimming speed can be portrayed as follows :

  sustained speed  high speed   burst speed  
red muscle in action  yes     
white muscle in action 
   aerobic condition yes  yes   
   anaerobic condition yes   yes  yes 


The red muscles are located deep within the body, and appear to be more important at the anterior part of the fish. They extend from the vertebral column to a lateral subcutaneous position. In contrast to other fishes, the proportion of red muscle does not seem to increase with the size of the tuna, probably because of greater muscle efficiency and labor sharing between red and white muscles, to which both endothermy and thermoregulation could contribute (Graham et al., 1983).

Muscle
Muscle

Heart and white muscle aerobic capacities are significantly greater in tunas than in billfishes and other scombrids.

Recovery from intense activities

Furthermore, tunas and billfishes are capable of recovering more quickly than other fish after intense activities, such as that involved in capture of prey. For some tunas, the rates of removal of lactate from the blood and white muscle tissue approximate the rates measured in mammals, which allows the tuna to recover within two hours (Dickson, 1995).

Thermoregulation in tuna

As a consequence of swimming constantly to maintain hydrostatic equilibrium (Magnuson, 1973) and oxygenate the blood (Roberts,  1978), muscular metabolism continuously generates heat as a byproduct. Tunas get rid of this excess, but, on the other hand, the heat can be used by the tuna to enable them to forage in cold waters.

Metabolic mechanism for thermoregulation

Among all bony fish, the Thunnini are unique in their ability to regulate their body temperatures, due to a complex counter-current heat exhanger system, also called the rete mirabile (miraculous network) (Stevens and Neil, 1978). The only other fishes with this system are some sharks of the family Lamnidae (Collette, 1978).

Rete mirabile
Rete mirabile (from Weinheimer, 2003)

The tuna maintain their body temperatures above that of the ambient water by passing arterial blood through vascular countercurrent heat exchangers. All species of tuna have a lateral rete, consisting of small arteries branching from the lateral subcutaneous arteries and small veins emptying into the lateral veins (Graham et al., 1983). In addition, many species of tuna also have a central rete within the vertebral haemal canal, consisting of arteries from the dorsal aorta and veins to the posterior cardinal veins (Stevens and Neil, 1978). The arterial blood is, then, warmed by the venous blood that flows through the red swimming muscles (Holland et al., 1992).

The rete mirabile retains between 70 and 99 % of the heat produced by the red muscle fibers, and provide a barrier between the red muscle and the environment (Graham et al., 1983). However, when excessive temperatures have been generated by heavy exercise, tunas appear to be able to control the efficiency of the heat exchangers by closing down some blood vessels of the rete mirabile, allowing heat to dissipate into the colder ambient water (Bushnell and Holland, 1997).

Measurements of body temperatures and ambient temperatures with histological analyses of the rete mirabile show that tunas as small as 207 mm in length can maintain their body temperatures more than 3°C above the ambient temperature, and thus can be considered to be endotherms (Graham et al., 1983). Tuna body temperatures are often 10°C greater than those of ambient water. The maximum temperature difference was recorded for an Atlantic bluefin tuna, for which the body temperature was 21.5°C greater than the surrounding water (Graham et al., 1983).

The thermoregulatory system cannot conserve heat indefinitely, and when a fish has been foraging in deep, cold water for an extended period, its body temperature decreases. When this happens, it can ascend to warmer water and disengage its thermoregulatory system to allow rapid warming of the tissues (Holland et al., 1992).

Behavioural mechanisms for thermoregulation

Combined with the physiological mechanisms, movements into cooler water will facilitate heat dissipation (Bushnell and Holland, 1997).

Advantages of thermoregulation

Thermoregulation allows the tunas to sustain high swimming speeds for long periods and to recover quickly after prolonged exertion (Carey et al., 1971), because most biochemical reactions proceed more rapidly at higher temperatures. Therefore, according to Bushnell and Holland, 1997, elevated body temperatures allow:

red muscle to contract more quickly, approaching the contraction rate of white muscle and consequently, contributing to high-speed swimming resulting from white muscle contractions
more rapid transfer of oxygen from blood to muscle cells
more rapid recovery, by enhancing the breakdown of lactic acid


In addition, being "warm bodied" allows the tunas to have a good vision at significant depths by maintaining their brains and eyes at greater than ambient temperatures (Bushnell and Holland, 1997). It also allows the tuna to be more sensitive to thermal gradients (Sharp and Dizon, 1978).
Also, because of that, the tuna can forage beneath the thermocline, in deep water, without suffering radical decreases in their core temperature. For example, a bigeye tuna was observed to dive 250 meters in one minute, going from 24°C to 9°C water (Holland et al., 1992).

 

Trophic relations and growth

Growth stages

The following three stages can be distinguished:

larvae (recently hatched individuals which are considerably different in appearance from juveniles or adults)
juveniles (similar in appearance to adults, but sexually immature)
adults (sexually mature fish)

Trophic position of larvae

Larvae of tunas and tuna-like fishes live in warm surface waters and feed primarily on the zooplankton including small crustaceans and larvae of crustaceans, fishes, molluscs and jelly-fish. Larvae of tunas and tuna-like species are preyed upon by zooplankton foragers, such as larger larvae and early juveniles of pelagic fishes. Cannibalism is, therefore, an important cause of mortality for tuna larvae.

Trophic position of juveniles and adults

Tunas and tuna-like fishes in the oceanic food web

Tunas and billfishes prey on fish, squid and crustaceans. The larger individuals (wahoo, bonitos, tunas and billfishes), which feed on pelagic fishes, are positioned at the top of the trophic web. The smaller individuals (juvenile tunas and billfishes, mackerels and seerfishes) prey on zooplankton (mainly crustaceans) and constitute part of the ration of large scombroids, sharks, cetaceans and seabirds. Analyses of stomach contents of yellowfin and skipjack tuna indicate that they feed on small epipelagic fishes between 1 and 10 cm in length (Roger, 1994). Since these preys of yellowfin and skipjack feed directly on zooplankton (mainly copepods), it seems that the tunas are at the top of a short food web, which is probably very efficient from the point of view of energetics.

Position of tunas and tuna-like fishes in the oceanic food web
Position of tunas and tuna-like fishes in the oceanic food web

Food items

Tunas and billfishes are opportunistic feeders. At the species level, they do not have strong preferences for certain types of prey. However, on a regional scale and at a given time, a few species may represent almost all of the food of fish of a specific age group (Cayré et al., 1988). Tunas and billfishes prey on pelagic or epipelagic fishes (including juveniles of tunas), crustaceans and cephalopods (squids). Yellowfin and bigeye tunas as well as swordfish feed on mesopelagic fishes (Ménard et al., 2000, Allain, 2005). Coastal tunas feed on neritic and epipelagic prey (Olson and Boggs, 1986). Larger tunas feed on small pelagic fishes such as mackerels, small tunas, carangids or flying fishes.

Example of preys that are often found in the stomach of tunas
Example of preys that are often found in the stomach of tunas

Foraging behavior of juveniles and adults

Tunas and billfishes are predators that locate their prey visually. To satisfy their food requirements tunas and billfishes have to swim long distances. Their type of locomotion is, therefore, particularly adapted to the search for prey in a large volume of water with the least expenditure of energy. However, they appear less effective than transient predators, such as esocids, in actually capturing the prey (Webb, 1984). To compensate for this, tunas tend to break up schools of prey, producing disorientation and straggling, and/or search for prey in schools (Webb, 1984; Partridge, 1982). Tunas can detect minute traces of scents of oils, proteins and amino-acids of the mucus layer produced by their prey. When prey is detected, some tunas show changes in their behavior consisting of a general increase of activity (also called frenzy): increase in swimming speed, change in swimming pattern, jaw snapping and display of dark stripes on the flanks. Tropical tunas and swordfish often dive down at significant depths below the thermocline (commonly at 500 m) to feed on mesopelagic fishes (Holland et al., 1992). It is commonly believed that tunas feed during the day. However, sonic tracking experiments show that some tunas feed also at dusk, when mesopelagic micronecton migrate toward the surface (Bard et al., 1998).

Growth of juveniles and adults

Growth rates

Most scombrids grow rapidly and reach their adult sizes in a few years. Average growth rates vary according to the species, the age and the location. In general, larger tunas grow to about 40 to 55 cm the first year, then the annual growth rate ranges between 20 to 30 cm per year decreasing with age. Tuna species attaining only small sizes grow to 20 to 35 cm in the first year and their annual length increments rapidly decrease to less than 10 cm. In the Atlantic and Indian Oceans, several studies have shown that yellowfin grow rapidly during the first year, slowing their growth during the next one or two years and then having again a fast growth before gradually slowing down as the maximum size is approached. Seerfishes and mackerels have also a fast growth during their first years of life. Sizes of 35 to 45 cm at age 1 year are common.

Billfishes can grow to more than 80 cm during their first year of life. After this very fast juvenile growth, adult growth rates are comparable to those of tunas.

Weights and lengths ranges

The maximum weights attained by tunas range from about 1 to 2 kg for bullet and frigate tunas to more than 600 kg for Atlantic bluefin tuna. The maximum lengths attained by tunas range from about 50 cm for bullet and frigate tunas to more than 300 cm for Atlantic bluefin tuna.

Seerfishes, mackerels and bonitos are relatively small (less than 1 meter in length), except for some species of seerfishes such as the king mackerel or the narrow-barred king mackerel which grow to more than 240 cm, for 70 kg.

The smallest billfish is the Mediterranean spearfish, which reaches a maximum length of a little more than 180 cm. The largest billfishes are the black marlin and the Indo-Pacific blue marlin, which reach lengths of more than 4 m and weights of more than 600 kg.

Relative sizes of tuna main market species
Relative sizes of tuna main market species

Size

Common and maximum sizes of tunas and billfishes

Tunas (1)

Scientific name Common size (in cm) Maximum size (in cm) Maximum weight (in kg)
Auxis rochei  15-35  50 
Auxis thazard  25-40  58 
Euthynnus lineatus  30-65  70 
Euthynnus alleteratus  30-80  100  12 
Euthynnus affinis  30-60  100  13 
Katsuwonus pelamis  40-80  108  33 
Thunnus atlanticus  40-70  100  19 
Thunnus alalunga  40-100  127  40 
Thunnus tonggol  40-70  130  35 
Thunnus albacares  60-150  200  175 
Thunnus maccoyii  160-200  225  160 
Thunnus obesus  70-180  230  200 
Thunnus thynnus  80-200  300  650 


Bonitos (1)

Scientific name Common size (in cm) Maximum size (in cm) Maximum weight (in kg)
Cybiosarda elegans  35-45  50 
Sarda sarda  30-50  85  7.5 
other Sarda 30-50  100 
Allothunnus fallai  65-95  96  10 
Orcynopsis unicolor  40-90  130  13 
Gymnosarda unicolor  65-150  200  131 

* Sarda australis, S. chiliensis, S. orientalis, S. sarda

Seerfishes and mackerels (1)

Scientific name Common size (in cm) Maximum size (in cm) Maximum weight (in kg)
Rastrelliger faughni  20  0.75 
Rastrelliger brachysoma  15-25  35 
Rastrelliger kanagurta  15-25  35 
Grammatorcynus spp.  60  3.5 
Scomber spp.  15-30  40-50 
Scomberomorus multiradius  35  0.5 
Scomberomorus concolor  75-80 
Scomberomorus guttatus  75-80 
Scomberomorus niphonius  100  4.5 
Scomberomorus cavalla  20-70  170 
Scomberomorus commerson  30-90  220  45 
Gasterochisma melampus  74-164  164 
Acanthocybium solandri  100-170  210  80 


Billfishes (2)

Scientific name Common size (in cm) Maximum size (in cm) Maximum weight (in kg)
Tetrapterus georgei  160 BL  21 
Tetrapterus pfluegeri  200 BL  45 
Tetrapterus angustirostris  200 TL  52 
Tetrapterus belone  240 BL  70 
Tetrapterus albidus  130-210 BL  280 TL  82 
Tetrapterus audax  140-280 BL  350 TL  200 
Istiophorus albicans  125-210 BL  315 TL  58 
Istiophorus platypterus  140-240 BL  340 TL  100 
Xiphias gladius  115-190 BL  445 TL  540 
Makaira nigricans  230-345 TL  375 TL  580 
Makaira indica  170-210 BL  448 TL  700 
Makaira mazara  200-300 BL  447 TL  900 

Notes for billfishes: BL = Body Length, TL = Total Length

References:
(1): Collette and Nauen (1983)
(2): Nakamura (1985)

International Game Fish Association (IGFA) records

Tunas and bonitos

Common name Record size (in cm) Record weight (in kg) Location and year of capture
Sarda chiliensis  6.3  off Baja California, 1980 
Euthynnus lineatus  11.8  off Baja California, 1991 
Euthynnus alleteratus  92.7  12.2  off Florida, 1976 
Katsuwonus pelamis  99  18.9  off Mauritius island, 1982 
Thunnus alalunga  123  40  off Canary Islands, 1972 
Acanthocybium solandri  72  off Baja California, 1996 
Thunnus albacares  208  176.4  west coast of Mexico, 1977 
Thunnus obesus  236  197.3  off Peru, 1957 
Thunnus thynnus  304  679  off Nova Scotia, 1979 


Seerfishes and mackerels

Common name Record size (in cm) Record weight (in kg) Location and year of capture
Scomber japonicus  1.9  off Baja California, 1986 


Swordfish and billfishes

Common name Record size (in cm) Record weight (in kg) Location and year of capture
Istiophorus albicans  61.4  off Nigeria, 1991 
Tetrapterus albidus  82.5  off Brazil, 1979 
Istiophorus platypterus  327.7  100.2  off Galapagos, 1947 
Tetrapterus audax  224.0  off New Zealand, 1986 
Xiphias gladius  445  536.1  off Chile, 1953 
Makaira mazara  624.1  off Hawaii, 1982 
Makaira nigricans  636.0  off Brazil, 1992 
Makaira indica  442  707.6  off Peru, 1953 


Source: IGFA (1995), note that IGFA records are not anymore on public domains and records might have changed since 1995.

Sexual dimorphism

Sexual dimorphism is observed with billfishes. For example, Atlantic Blue marlin exhibits sexually dimorphic growth patterns: somatic growth of male slows at about 100 kg round weight and males do not exceed 150 kg, while females can reach up to 910 kg (Wilson et al., 1991). Similarly, swordfish exhibit a sexual dimorphism of growth: males grow more slowly and reach a lower asymptotic length than females.

Longevity

Longevities of tunas vary from a few years for the smaller tunas to 12 to 15 years for the larger tunas. The longevity record for tunas is about 20 years for the Atlantic bluefin tuna (Cort, 1990) or 25 years for the southern bluefin tuna (Gunn et al., 2008). Longevities of 15 to 27 years (Pacific blue marlin) or 28 years (Indo-Pacific blue marlin) have been estimated for billfishes and for swordfish. Longevities of seerfishes and mackerels are moderate with some records at 16 years for the Spanish mackerel.

Natural mortality

For larger tunas and billfishes, adult natural mortalities range from 0.2 to 0.6. Juvenile natural mortalities are higher. Little is known on natural mortalities of seerfishes and mackerels.

 

Reproduction

Spawning

Spawning behavior

Tuna spawn in open water close to the surface. Eggs are released by females in several batches. For example, yellowfin tuna in the Pacific spawn nearly every day. However, for some species like the bluefin species, spawning is more seasonal.

Spawning areas and seasons

Tunas spawn in areas where the survival of their larvae is greatest. Most species of tunas spawn only in waters where the surface temperatures are greater than 24°C. Tropical tunas appear to spawn in equatorial areas all year around and at higher latitudes during the warm seasons. Albacore and bigeye appear to migrate annually from temperate feeding areas to tropical spawning areas. Bigeye larvae are less abundant than those of other tropical tunas, and are found mainly in equatorial waters in which the temperatures are greater than 28°C (Collette and Nauen, 1983). Atlantic bluefin, Pacific bluefin and southern bluefin tuna exhibit a homing behavior when they mature, and return to restricted areas in the Atlantic, Pacific and Indian Oceans to spawn. It is commonly accepted that there is a homing behavior, but to a lesser extent, in yellowfin in the Atlantic Ocean. Billfishes appear to spawn seasonally in warm tropical and subtropical waters.

Maturity and fecundity

Maturity

With the exception of bluefin tunas (Thunnus thynnus, T. orientalis and T. maccoyii), most tunas, seerfishes, mackerels and billfishes reach their age of maturity between 2 and 5 years of age. Due to their sexual dimorphism of growth, male billfishes are mature at a smaller size than female billfishes.

 

Maturity of tunas and billfishes

Tunas

Scientific name

Age

Size

Weight

Auxis rochei 

 

35 cm

 

Auxis thazard 

 

~30 cm

 

Euthynnus alleteratus 

 

40-50 cm

 

Euthynnus affinis 

 

45-50 cm

 

Katsuwonus pelamis 

2 years

Female: 42-50 cm
Male: 45-52 cm

 

Thunnus alalunga 

5 years

90 cm

15 kg

Thunnus albacares 

2.5-3 years

100-110 cm

20-30 kg

Thunnus maccoyii 

11 years

 

 

Thunnus obesus 

3-3.5 years

100-110 cm

 

Thunnus thynnus (East Atl.)

4 years

115 cm

30 kg

Thunnus thynnus (West Atl.)

8 years

190 cm

120 kg



Bonitos

Scientific name

Age

Size

Weight

Sarda sarda 

 

~40 cm

 



Seerfishes and mackerels

Scientific name

Age

Size

Weight

Scomberomorus guttatus 

1-2 years

40-50 cm

 

Scomberomorus maculatus 

2 years

25-35 cm

 

Scomberomorus cavalla 

4 years

60-70 cm

 

Scomberomorus commerson 

 

70-90 cm

 

Acanthocybium solandri 

2 years

90 cm

 



Billfishes

Scientific name

Age

Size (LJFL)

Weight

Tetrapterus pfluegeri 

 

150 cm

17-19 kg

Tetrapterus albidus 

 

Female: ~150 cm
Male: ~140 cm

 

Istiophorus albicans 

 

Female: 160-180 cm
Male: ~140 cm

Female: 18-20 kg
Male: 10 kg

Xiphias gladius 

3.5 years

150-160 cm

 

Makaira nigricans 

 

Female: ~250 cm

120 kg

Makaira indica 

 

Female: ~180 cm
Male: 130-160 cm

Female: ~200 kg
Male: 60-80 kg

Makaira mazara 

2-4 years

130-140 cm

Female: 60-80 kg
Male: 40-50 kg

Fecundity

The batch fecundities of most species of tunas range from 2 to 70 million eggs, the lowest fecundity being for albacore and the highest for skipjack tuna and other small-sized tunas. Known batch fecundities of mackerels range from 300 000 to 1 500 000 eggs. Little is known on fecundities of seerfishes. Fecundity of wahoo has been estimated to 6 million eggs. Less is known on the reproductive biology of billfishes, but batch fecundity is estimated to range between 1 and 7 millions of ovocytes. Swordfish batch fecundity was estimated to 3.9 millions eggs in the Atlantic.

Maturity and fecundity parameters of the principal market species of tunas

Scientific name

Size and age at maturity

Annual batch fecundity

Katsuwonus pelamis 

about 3 years and 42 to 45 cm  

7 to 76 million eggs 

Thunnus alalunga 

about 5 years and 90 cm  

2 to 3 million eggs 

Thunnus albacares 

about 3 years and 100 cm  

4 to 60 million eggs 

Thunnus obesus  

about 3 years and 100 cm  

4 to 60 million eggs  

Thunnus thynnus 

about 4 years and 105 to 120 cm 

5 to 30 million eggs 

Sex ratio

It has been shown that for yellowfin, bigeye and albacore, the sex-ratio changes with the age of the fish with a predominance of males for the larger sizes. A predominance of females has also been observed for medium-sized Atlantic bluefin tuna. For skipjack, differences in the numbers of males and females have been observed locally. Predominance of females at older ages is observed for several species of billfishes.

 

Acknowledgment

Michel Goujon and Jacek Majkowski, who compiled the information contained in this presentation, are grateful to:
- Aureliano Gentile for editing and incorporating information into FIGIS and
- Ignacio de Leiva, Marcella Pesce, Yves Jaques and A. Gentile for their contribution to the former version of this document.

 

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