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

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

 

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.

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.

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.

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.

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 :

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).

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).

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.

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.

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.

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	9
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	5
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	1
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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]]> Michel Goujon and Jacek Majkowski, 2000 Aquatic Species - fact sheets Espèces aquatiques - fiches d'informations Especies acuáticas - hojas informativas Виды гидробионтов. Информационные бюллетени صحائف وقائع الانواع المائية 水生种类情况说明 search interface http://www.fao.org/fishery/species/search 413 153075 12251 Tuna resources Les ressources en thonidés Recursos atuneros 2295 Capture fisheries topics and activities 156463 16917 Tuna fisheries and utilization Pêcheries thonières et utilisation du poisson Pesquerías y utilización del atún 2295 Capture fisheries topics and activities 156462 16916 FAO activities on tuna Activités de la FAO portant sur le thon Actividades de la FAO sobre el atún 2295 Capture fisheries topics and activities