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Scombroidei (Barracudas, Tunas, Marlins, and Relatives)

Scombroidei

(Barracudas, tunas, marlins, and relatives)

Class Actinopterygeii

Order Perciformes

Suborder Scomboidei

Number of families 6


Evolution and systematics

The first modern definition of the scombroid fishes as a suborder was by Regan in 1909. He clearly separated scombroids from percoid families, such as the jacks (Carangidae) and dolphinfishes (Coryphaenidae). Regan recognized four divisions within the Scombroidei: Trichiuriformes (Gempylidae and Trichiuridae), Scombriformes (Scombridae), Luvariformes (Luvaridae), and Xiphiiformes (Xiphiidae, Istiophoridae, and three fossil families). The suborder was redefined by Collette et al. (1984), and the Luvaridae were shown to be a highly specialized oceanic member of the typically reef-associated surgeonfishes (Acanthuroidei) by Tyler et al. (1989). Collette et al. (1984) included the Scombrolabricidae in the Scombroidei as its most primitive member. An alternative definition of the Scombroidei proposed by Johnson in 1986 excludes the Scombrolabracoidei but includes the barracudas (Sphyraenidae) as the most primitive member of the Scombroidei.

The 6 families are Sphyraenidae (1 genus, 20 species), Trichiuridae (9 genera, 32 species), Gempylidae (16 genera, 23 species), Scombridae (15 genera, 53 species), Xiphiidae (1 genus, 1 species), and Istiophoridae (3 genera, 9 species).

Physical characteristics

Perciform fishes with epiotic bones of the skull separated from each other by the supraoccipital bone; gill membranes

free from the isthmus; premaxillae beak like, upper jaw not protrusile, predorsal bones lost (except for a small one in Ruvettus, Thyrsites, and Tongaichthys, and three well-developed ones in Gasterochisma); second epibranchial bone of pharyngeal arch extending over top of the third infrapharyngobranchial bone (except in Gasterochisma); 24 or more vertebrae; interorbital commissure of the supraorbital lateral line canals incomplete or absent

Distribution

These fishes are found in marine and estuarine waters of tropical and temperate oceans of the world. One species of Spanish mackerel moves long distances up the Mekong River.

Habitat

Most scombroid fishes are epipelagic; some are mesopelagic.

Behavior

Some scombroids (such as mackerels) form very large schools while others (such as wahoo and snake mackerels) are essentially solitary.

Feeding ecology and diet

Most scombroids are active predators, feeding on a wide variety of fishes, squids, and crustaceans, but some (such as the mackerels) filter small planktonic organisms out of the water with their long gillrakers.

Smaller species of scombroids, such as mackerels, fall prey to all larger predacious sea animals. Whales, porpoises, sharks, tunas, bonito, bluefish, and striped bass take a heavy toll. Cod often eat small mackerel; squids destroy great numbers of young fish; and seabirds of various kinds follow and prey upon the schools when these are at the surface.

Medium-sized scombroids such as bonitos and skipjack are preyed upon by tunas, billfishes, and sharks. Predators of large tunas like the bluefin include killer whales and such sharks as the white shark and the mako shark. Large billfishes are so active and powerful that they have few enemies but are preyed upon by killer and sperm whales and mako sharks.

Reproductive biology

Scombroids are dioecious (separate sexes) and most display little or no sexual dimorphism in structure or color pattern. Batch spawning of most species takes place in tropical and subtropical waters, frequently inshore. The eggs are pelagic and hatch into planktonic larvae.

Conservation status

Populations of three species, swordfish (Xiphias gladius), Atlantic bluefin tuna (Thunnus thynnus), and Atlantic albacore (Thunnus alalunga), have been greatly reduced by fishing. All three are listed by the IUCN as Data Deficient. In addition, the IUCN categorizes the Monterrey Spanish mackerel (Scomberomorus concolor) as Endangered, the southern bluefin tuna (Thunnus maccoyii) as Critically Endangered, and the bigeye tuna (Thunnus obesus) as Vulnerable.

Significance to humans

Many species of scombroid fishes are of great importance as food fishes—mackerel, Spanish mackerel, bonito, and tuna—and as sport fishes—Spanish mackerel, tuna, swordfish, and marlin.

Species accounts

List of Species

Snake mackerel
Sailfish
Blue marlin
Wahoo
Skipjack tuna
Atlantic mackerel
King mackerel
Albacore
Atlantic bluefin tuna
Great barracuda
Largehead hairtail
Swordfish

Snake mackerel

Gempylus serpens

family

Gempylidae

taxonomy

Gempylus serpens Cuvier, 1829, Tropic of Cancer.

other common names

French: Escolier serpent; Spanish: Escolar de canal.

physical characteristics

Maximum length approximately 40 in (1 m), commonly to 24 in (60 cm). Body greatly elongate and strongly compressed. Tips of upper and lower jaws with cartilaginous processes. Three immovable and zero to three movable fangs anteriorly in upper jaw. First dorsal fin long with 26–32 spines, second dorsal fin with 11–14 soft rays followed by five or six finlets. Caudal fin well developed. Scales absent except on posterior part of body.

distribution

Worldwide in tropical and subtropical seas; adults also caught in temperate waters.

habitat

Strictly oceanic, epipelagic and mesopelagic from the surface to depths of 656 ft (200 m).

behavior

Usually solitary. Adults migrate to the surface at night; larvae and juveniles stay near the surface only during the day.

feeding ecology and diet

Feed on fishes such as lanternfishes, flyingfishes, sauries, and scombrids and on squids and crustaceans.

reproductive biology

Males mature at approximately 17 in (43 cm) standard length, females at 20 in (50 cm). Spawn in tropical waters throughout the year. Fecundity is estimated at 300,000 to one million eggs.

conservation status

Not threatened.

significance to humans

There is no directed fishery for snake mackerel, but it sometimes appears as bycatch in the tuna long-line fishery.


Sailfish

Istiophorus platypterus

family

Istiophoridae

taxonomy

Istiophorus platypterus (Shaw, 1792), Indian Ocean. Some authors, such as Nakamura (1985), differentiate the Atlantic sailfish, I. albicans (Latreille, 1804), as a separate species.

other common names

French: Voilier; Spanish: Pez vela.

physical characteristics

Sailfishes reach a maximum size of approximately 11 ft (3.5 m) total length and 220 lb (100 kg). Body fairly compressed. Two dorsal and two anal fins, the first dorsal fin sail-like and remarkably higher than greatest body depth, with 42–49 rays. Second dorsal fin with six or seven rays, slightly posterior to second anal fin which also has six or seven rays. Pectoral fins moderate, 18–20 rays. Pelvic fins extremely long, almost reaching the anus, depressable into a groove, with one spine and several rays tightly fused together. Jaws and palatine bones with small, file-like teeth. Gill rakers absent. Left and right branchiostegal membranes broadly united. Vertebrae, 24. Swim bladder made up of many small bubble-shaped chambers.

distribution

Most researchers consider the sailfish to be a single pantropical species occurring in all three major oceans.

habitat

An epipelagic and oceanic species, usually found above the thermocline. Sailfishes have a strong tendency to approach continental coasts, islands, and reefs.

behavior

Sailfishes occasionally form schools or smaller groups of 3–30 individuals, but more often occur in loose aggregations over a wide area.

feeding ecology and diet

Feeding behavior has been observed by fishermen: One or several sailfish locate a school of prey fish (such as sardines, anchovies, mackerel, or jack mackerel) and pursue the school at half speed with their fins half-folded back into the grooves. They then drive at the prey at full speed with fins completely folded back and make sharp turns with fins expanded to confront part of the school and strike the prey with their bills. They feed on the killed or stunned fish, usually head first as well as on a variety of fishes, crustaceans, and squid.

reproductive biology

Spawning occurs with males and females swimming in pairs or with two or three males chasing one female. Sailfishes spawn throughout the year in tropical and subtropical waters with peak spawning in local summer seasons. Ripe ovarian eggs are approximately 0.03 in (0.85 mm) in diameter and have a single oil globule. Eggs shed from a captured female averaged 0.05 in (1.30 mm) in diameter.

conservation status

Not threatened.

significance to humans

Sailfishes are often taken as bycatch by the commercial surface tuna long liners. United Nations Food and Agriculture Organization (FAO) catch statistics for 1991–2000 show catches of 11.1–23.7 thousand tons (10.1–21.5 thousand metric tons) per year by 42 countries. Sailfishes are primarily important as a sportsfish taken by trolling at the surface. The all-tackle gamefish record is a 221-lb (100.2-kg) fish taken off Santa Cruz Island, Ecuador.


Blue marlin

Makaira nigricans

family

Istiophoridae

taxonomy

Makaira nigricans Lacepede, 1802, Bay of Biscay. Some authors, such as Nakamura (1985), differentiate the Indo-Pacific blue marlin, M. mazara (Jordan and Snyder, 1901), as a separate species.

other common names

French: Makaire bleu; Spanish: Aguja azul.

physical characteristics

Blue marlin reach approximately 16 ft (5 m) in total length and weigh more than 1,984 lb (900 kg). Body not very compressed, nape highly elevated, body deepest at level of pectoral fins. Two dorsal and two anal fins. First dorsal fin with 39–43 rays; height of anterior lobe less than greatest body depth, not sail-like. Second dorsal fin with six or seven rays, slightly posterior to second anal fin. Pectoral fins with 20–23 rays, depressible against sides of the body. Pelvic fins shorter than pectoral fins with one spine and two rays. Lateral line looped. Body covered with densely imbedded scales, each with one or two long, acute spines. Left and right branchiostegal membranes broadly united. Vertebrae, 24. Swim bladder made up of many small bubble-shaped chambers. Body blue dorsally, silvery white ventrally, first dorsal fin membrane blue-black, unspotted; body has approximately 15 obscure vertical light bars.

distribution

Most researchers consider the blue marlin to be a single pantropical species occurring in all three major oceans. Blue marlin are the most tropical of the billfishes, chiefly distributed in equatorial areas.

habitat

Epipelagic zone of oceans, usually waters with surface temperatures of 71.6–87.8°F (22–31°C).

behavior

Observations suggest that marlins use their bills to stun their prey.

feeding ecology and diet

Feed mostly in near-surface waters but sometimes make trips to relatively deep waters for feeding. Prey includes dolphin-fishes, tuna-like fishes, particularly frigate tunas, and squids.

reproductive biology

Little is known about spawning grounds or seasons. The eggs are very small, approximately 0.04 in (1 mm) in diameter, and pelagic, hatching into planktonic larvae.

conservation status

Not threatened.

significance to humans

Being excellent foodfishes, all species of marlin are of some importance to fisheries, particularly in Japan. They are mostly caught on long lines incidental to the target tuna species. FAO catch statistics for 1991–2000 show catches of 26.7–37.3 thousand tons (24.2–33.8 thousand metric tons) per year by 34 countries. Blue marlin are especially important to sportfishermen and are much sought after off Cuba and on the Bahamas side of the Straits of Florida. The all-tackle gamefish record is a 1,402-lb (636-kg) fish taken off Vitória, Brazil.


Wahoo

Acanthocybium solandri

family

Scombridae

taxonomy

Acanthocybium solandri (Cuvier, 1832), type locality unknown.

other common names

French: Thazard-bâtard; Spanish: Peto.

physical characteristics

Maximum size 83 in (210 cm) fork length weighing 183 lb (83 kg) or more. Body very elongate, fusiform, and only slightly compressed. Mouth large with strong, triangular, compressed, and finely serrate teeth closely set in a single series. Snout approximately as long as rest of head. Gill rakers absent. Two dorsal fins, the first consisting of 23–27 spines, the second with 12–16 rays followed by eight or nine finlets. Anal fin of 12–14 rays followed by nine finlets. Body covered with small scales. Swim bladder present. Vertebrae, 62–64. Back iridescent bluish green, sides silvery with 24–30 cobalt-blue vertical bars.

distribution

Tropical and subtropical waters of the Atlantic, Pacific, and Indian oceans including the Caribbean and Mediterranean seas.

habitat

Epipelagic zone ocean.

behavior

Frequently solitary or forming small, loose aggregations rather than compact schools.

feeding ecology and diet

Piscivorous, preying on pelagic fishes such as scombrids, porcupinefishes, flyingfishes, herrings, scads, and lanternfishes and on squids.

reproductive biology

Spawning seems to extend over a long period. Fish in different maturity stages are frequently caught at the same time. Fecundity is believed to be quite high; 6 million eggs were estimated for a 52-in (131-cm) female.

conservation status

Not threatened.

significance to humans

There do not appear to be any organized fisheries for wahoo, but it is greatly appreciated when caught. FAO catch statistics for 1991–2000 show catches of 2,121–3,460 tons (1,924–3,139 metric tons) per year by 30 countries. In many areas (Caribbean, Hawaii, Great Barrier Reef), wahoo is more important as a gamefish taken on light to heavy tackle through surface trolling with spoons, feather lures, or strip bait. The all-tackle gamefish record is a 159-lb (71.9-kg) fish taken off Baja California.


Skipjack tuna

Katsuwonus pelamis

family

Scombridae

taxonomy

Katsuwonus pelamis (Linnaeus, 1758), "pelagic, between the tropics."

other common names

French: Bonite à ventre rayé; Spanish: Listado.

physical characteristics

Maximum fork length approximately 43 in (108 cm) corresponding to a weight of 72–76 lb (32.5–34.5 kg), commonly to 31 in (80 cm) and 18–22 lb (8–10 kg). Body fusiform, elongate, and rounded. Two dorsal fins separated by a narrow interspace, the first with 14–16 spines, the second dorsal and anal fins followed by seven to nine finlets. Pectoral fins short, with 26 or 27 rays. Body naked except for anterior corselet and lateral line. Caudal peduncle very slender with a strong lateral keel between two smaller keels. Swim bladder absent. Gill rakers numerous, 53–63 on first gill arch. Back dark purplish blue, lower sides and belly silvery, with four to six very conspicuous longitudinal dark bands.

distribution

Cosmopolitan in tropical and warm-temperate seas but absent from the Black Sea.

habitat

An epipelagic oceanic species with adults distributed within the 59°F (15°C) isotherm. Aggregations of this species tend to be associated with convergences, boundaries between cold and warm water masses. Depth distribution ranges from the surface to about 853 ft (260 m) during the day.

behavior

Skipjack show a strong tendency to school in surface waters. Schools are associated with birds, drifting objects, sharks, whales, and other tuna species.

feeding ecology and diet

Skipjack are opportunistic feeders preying on any forage available. Feeding activity peaks in early morning and late afternoon. Food items include fishes, crustaceans, and mollusks.

reproductive biology

Skipjack spawn in batches throughout the year in equatorial waters and from spring to early fall in subtropical waters. The spawning season becomes shorter as distance from the equator increases. Fecundity increases with size but is highly variable. The number of eggs per season in females 16–24 in (41–87 cm) fork length ranges from 80,000 to two million.

conservation status

Not threatened.

significance to humans

Skipjack make up approximately 40% of the world's total tuna catch and have come to replace yellowfin as the dominant commercial species of tuna. Catches of skipjack were reported to FAO by 94 countries for 1991–2000, 1,584– 2,191 thousand tons (1,437–1,988 thousand metric tons) per year. The highest catches reported for 2000 were by Japan, 376 thousand tons (341 thousand metric tons), and Indonesia, 298 thousand tons (270 thousand metric tons). Skipjack are taken at the surface, mostly with purse seines and pole-and-line gear, occasionally with long lines. They are marketed fresh, frozen, and canned (as light-meat tuna). They are also a game fish, the all-tackle gamefish record is a 45-lb (20.5-kg) fish caught on Flathead Bank, Baja California.


Atlantic mackerel

Scomber scombrus

family

Scombridae

taxonomy

Scomber scombrus Linnaeus, 1758, Atlantic Ocean.

other common names

French: Maquereau commun; Spanish: Caballa del Atlantico.

physical characteristics

Maximum fork length is 22 in (56 cm), commonly to 19 in (30 cm). Body fusiform, tapering rearward to a very slim caudal peduncle and anteriorly to a pointed snout. Eyes large with socalled adipose eyelids covering front and hind margins of the eye except for a slit over the pupil. Mouth large, filled with small, sharp, conical teeth in upper and lower jaws. Gill rakers, 30–36 on lower limb of first gill arch. Two widely separated dorsal fins, the first with 11–13 spines, the second with 11 or 12 rays. Both second dorsal and anal fins followed by five finlets. Entire body covered with small scales. Swim bladder usually absent. Vertebrae, 31. Upper surface dark steely to greenish blue. Body barred with 23–33 dark transverse bands; belly unmarked.

distribution

North Atlantic Ocean, including the Baltic, Mediterranean, and Black seas. Replaced by other species of Scomber in other oceans.

habitat

An epipelagic and mesodemersal species, most abundant in cold and temperate shelf areas.

behavior

Mackerel are swift-moving, swimming with very short sidewise movements of the rear part of the body and the powerful caudal fin. They need so much oxygen that they must swim constantly to bring sufficient water across their gill filaments. Mackerel gather in dense schools of fish that are approximately the same size and age. They overwinter in moderately deep water along the continental shelf and move inshore and northward in the spring.

feeding ecology and diet

Atlantic mackerel are opportunistic carnivores that swallow their food whole. Food is captured by active pursuit or by passive filtration with the gill rakers. Juveniles feed on zooplankton. Adults also eat crustaceans but add squids and small fishes to their diet.

reproductive biology

In the western North Atlantic, spawning takes place from Chesapeake Bay to Newfoundland, beginning in the south in spring and progressively extending northward into the summer. Most spawning occurs within 10–30 mi (16–48 km) of shore. Mackerel do not begin spawning until the water has warmed to approximately 46.4°F (8°C). The chief production of eggs takes place at temperatures of 48.2–57.2°F (9–14°C). Maturity is attained at 2–3 years of age. Estimates of fecundity range from 285,000 to 1.98 million eggs for females 12–17 in (307–438 mm) fork length. The eggs are 0.04–0.05 in (1.09–1.39 mm) in diameter, have one oil globule, and generally float in the surface water layer above the thermocline.

conservation status

Not threatened.

significance to humans

Mackerel are delicious fish but do not keep as well as fishes that have less oil in their tissues. There are important fisheries in the northwest Atlantic, northeast Atlantic, and Mediterranean and Black seas. FAO catch statistics for 1991–2000 show catches of 6.16–9.42 thousand tons (5.59–8.55 thousand metric tons) per year by 36 countries. Atlantic mackerel are caught mainly with purse seines. Mackerel also are taken by anglers; the all-tackle world record is a 3-lb (1.2-kg) fish taken off Norway.


King mackerel

Scomberomorus cavalla

family

Scombridae

taxonomy

Scomberomorus cavalla (Cuvier, 1829). Based on Marcgrave's guarapucu, Brazil.

other common names

French: Thazard barre; Spanish: Carite lucio.

physical characteristics

Maximum size 98 in (250 cm) fork length and 79–99 lb (36–45 kg), commonly to 28 in (70 cm). Body elongate, strongly compressed. Snout much shorter than rest of head. Posterior portion of maxilla exposed, reaching to a vertical with hind margin of eye. Gill rakers on first arch few, 6–11, usually 8–10. Two dorsal fins, scarcely separated, the first with 14–16 spines. Eight or nine dorsal finlets; 9 or 10 anal finlets. Lateral line abruptly curving downward below second dorsal fin. Body completely covered with small scales; no anterior corselet developed. Vertebrae, 41–43. Back iridescent bluish green, sides silvery, adults do not have bars or spots, but juveniles may have spots on sides. Unlike many other species of Spanish mackerels, adults have no black area in the first dorsal fin.

distribution

Confined to the western Atlantic Ocean from Massachusetts to Rio de Janeiro.

habitat

Epipelagic and neritic, often found in outer reef areas.

behavior

King mackerel are present throughout the year off Louisiana in the Gulf of Mexico, southern Florida, and the state of Ceará in northeastern Brazil. Large schools of king mackerel migrate north along the coast of the United States in spring and return south during the fall.

feeding ecology and diet

As for other members of the genus, food consists largely of fishes and small quantities of penaeid shrimps and squids. Various herring-like fishes are particularly important components of the diet.

reproductive biology

Spawning takes place from May through September in the western Gulf of Mexico, particularly in September at depths between 115 and 591 ft (35 and 180 m) over the middle and outer continental shelf. In Brazil, fecundity of females 25–48 in (63–123 cm) fork length ranges from 345,000 to 2,280,000 eggs.

conservation status

Not threatened.

significance to humans

King mackerel is an important species for recreational, commercial, and artisanal fisheries throughout their range. Eight nations reported to FAO catches of 6.0–13.1 thousand tons (5.4–11.9 thousand metric tons) per year from 1991 to 2000, but several other countries combine king mackerel with other species of Spanish mackerel, so the total catch and the number of countries fishing for this species is higher. Commercial fisheries in the southeastern United States use hook-and-line, snapper hooks, gill nets, and trolled lure or small cut bait. In Brazil, gill nets and trolling are major ways of catching king mackerel. In the United States, sport fishing with hook-and-line is practiced in North Carolina, Florida, Mississippi, and Louisiana. The all-tackle world game fish record is a 94-lb (42.18-kg) fish caught off San Juan, Puerto Rico.


Albacore

Thunnus alalunga

family

Scombridae

taxonomy

Thunnus alalunga (Bonnaterre, 1788), Sardinia.

other common names

French: Germon; Spanish: Atún blanco.

physical characteristics

Maximum fork length 50 in (127 cm). A large tuna, deepest at a more posterior point than in other tuna species, at or only slightly anterior to second dorsal fin. Two dorsal fins, separated by only a narrow interspace, the first with 11–14 spines, the second with 12–16 rays; anal fin with 11–16 rays; both second dorsal and anal fins followed by seven to nine finlets. Pectoral fins remarkably long, usually 30% of fork length or longer, reaching posteriorly well beyond origin of second dorsal fin. Teeth small and conical, in a single series. Gill rakers, 25–31. Caudal peduncle very slender with a strong lateral keel between two smaller keels. Corselet of large scales anteriorly; rest of body covered with small scales. Swim bladder present. Ventral surface of liver striated. Back metallic dark blue; lower sides and belly silvery white; second dorsal and anal fins yellow; anal finlets dark; white margin on posterior margin of caudal fin.

distribution

Cosmopolitan in tropical and temperate waters of all oceans and Mediterranean Sea, north to 45–50°N, south to 30–40°S. Offshore often extend into cooler waters.

habitat

Epipelagic and mesopelagic zones of ocean; abundant in surface waters of 60.1–66.9°F (15.6–19.4°C). Deeper-swimming large albacore are found in waters of 55.9–59.4°F (13.3–15.2°C).

behavior

Throughout their range, albacore migrate over great distances and appear to form separate groups at different stages of the life cycle. At least two stocks, northern and southern, are believed to exist in both the Atlantic and Pacific oceans.

feeding ecology and diet

Feeds on crustaceans, fishes, and squids.

reproductive biology

Albacore tend to spawn in subtropical waters, although they do spawn in tropical waters in some places. Albacore mature at approximately 5 years of age and 35 in (90 cm) fork length in the Atlantic Ocean. Fecundity increases with size generally. A 44-lb (20-kg) female may produce 2–3 million eggs per season released in at least two batches.

conservation status

Listed as Data Deficient by IUCN.

significance to humans

There are important fisheries for albacore in the Atlantic and Pacific oceans. FAO catch statistics for 1991–2000 show catches of 185–280 thousand tons (168–254 thousand metric tons) per year by 59 countries. The highest landings reported for 2000 were by Japan, 69 thousand tons (62.6 thousand metric tons), and Taiwan, 57.0 thousand tons (51.7 thousand metric tons). With increasing effort in surface fisheries, the world catch has been gradually declining, particularly in the Atlantic Ocean. Albacore are caught by four types of fishing operations: long lining, live-bait fishing, trolling, and purse seining. Albacore is packed as "white-meat" tuna. The all-tackle game fish record is an 88-lb (40.0-kg) fish caught in the Canary Islands.


Atlantic bluefin tuna

Thunnus thynnus

family

Scombridae

taxonomy

Thunnus thynnus (Linnaeus, 1758). Pacific bluefin were considered a subspecies of T. thynnus for many years but have recently been raised to species level (Collette et al., 2001) as T. orientalis Temminck and Schlegel, 1844.

other common names

English: Northern bluefin tuna; French: Thon rouge; Spanish: Atún.

physical characteristics

Maximum fork length more than 118 in (300 cm), commonly to 79 in (200 cm). A very large tuna, deepest near middle of first dorsal fin base. Two dorsal fins, separated by only a narrow interspace, the first with 11–14 spines, the second with 12–16 rays; anal fin with 11–16 rays, both second dorsal and anal fins followed by 7–10 finlets. Pectoral fins very short, less than 80% of head length, never reaching the interspace between the dorsal fins. Teeth small and conical in a single series. Gill rakers, 34–41. Caudal peduncle very slender with a strong lateral keel between two smaller keels. Corselet of large scales anteriorly; rest of body covered with small scales. Swim bladder large. Ventral surface of liver striated. Back metallic dark blue, lower sides and belly silvery white; first dorsal fin yellow or bluish, second dorsal reddish brown, anal fin silvery gray, anal finlets dusky yellow edged with black; no white margin on posterior margin of caudal fin.

distribution

North Atlantic Ocean from Labrador and Newfoundland south into Gulf of Mexico and Caribbean Sea. Replaced by the closely related Pacific bluefin tuna in the north Pacific.

habitat

Epipelagic, usually oceanic but seasonally coming very close to shore. Bluefin are found in moderately warm seas but are more tolerant of cold water than are most of their relatives. Offshore in the northwest Atlantic, large bluefin are taken at surface temperatures of 43.5–83.8°F (6.4–28.8°C). Tunas have evolved elaborate rete mirabilia, "wonder nets," of capillaries that act as countercurrent heat exchangers. These heat exchangers form thermal barriers that prevent metabolic heat loss and enable bluefin to maintain a high internal temperature, as high as 83.8°F (28.8°C) for a bluefin taken in 45.1°F (7.3°C) water.

behavior

Atlantic bluefin migrate long distances from their spawning grounds off Florida in the western Atlantic and in the Mediterranean Sea in the eastern Atlantic. Tag returns show there is some mixing between eastern and western Atlantic but there is ongoing debate about the proportion of individuals that cross the ocean.

feeding ecology and diet

Feed on a variety of fishes, crustaceans, and squids.

reproductive biology

Onset of maturity is at approximately 4–5 years. Large adults (10 years and older) spawn in the Gulf of Mexico and in the Mediterranean Sea. Females weighing 592–661 lb (270–300 kg) may produce as many as 10 million eggs per spawning season.

conservation status

Listed by IUCN as Data Deficient. Western Atlantic bluefin were fished intensively in the 1960s by purse seiners targeting small fish for canneries (Safina, 2001). Obvious depletion led to reduction in the east coast purse seine fleet. Western Atlantic bluefin catches averaged approximately 8,818 tons (8,000 metric tons) during the 1960s and 6,062 tons (5,500 metric tons) during the 1970s. During the 1970s, commercial targeting switched to large fish for export to Japan for sashimi. The offer to buy giant bluefin at $1.45 per pound (0.5 kg) (instead of the previous $0.20 to $0.50 per pound in autumn 1972) greatly increased U.S. fishing pressure on giant bluefin.

significance to humans

Important as both a food fish and a sport fish. FAO catch statistics for 1991–2000 show catches of 29.7–60.2 thousand tons (26.9–54.6 thousand metric tons) per year by 44 countries. The belly meat of bluefin, when containing much fat, reaches astronomical prices in the Japanese market for sashimi. Individual bluefin in prime condition have sold for as much as $68,000, approximately $45 per pound (0.5 kg), but a new record price of $173,600 (¥20 million) was reached for a 444-lb (201-kg) bluefin sold in Tokyo's Tsukiji Central Fish Market in January 2001. The all-tackle game fish record for a "giant" bluefin is a 1,497-lb (679-kg) fish taken off Nova Scotia.


Great barracuda

Sphyraena barracuda

family

Sphyraenidae

taxonomy

Sphyraena barracuda (Walbaum, 1792), West Indies.

other common names

French: Barracuda; Spanish: Picuda barracuda.

physical characteristics

Twenty-four vertebrae. Reaches 79 in (200 cm), commonly to 51 (130 cm). Body elongate and slightly compressed. Head large with a long, pointed snout. Mouth large, tip of maxilla reaching to or extending beyond anterior margin of the eye in adults. Lower jaw projecting beyond upper jaw without a fleshy tip. Strong, pointed vertical teeth of unequal sizes in both jaws and in roof of mouth. Two dorsal fins, far apart, the first with five strong spines, its origin slightly behind pelvic fin origin. Tip of adpressed pectoral fin reaching to or extending beyond pelvic fin origin. Gill rakers are absent. Lateral line well developed, straight, with 80–90 scales. Deep green to steel gray above, sides silvery, abruptly becoming white on ventral surface. Adults have several oblique dark bars, usually 18–22, on upper sides and usually have several to many scattered inky blotches on posterior part of lower sides.

distribution

Worldwide in tropical and subtropical waters except eastern Pacific Ocean.

habitat

Small individuals are mostly found in shallow waters over sandy and weedy bottoms, often forming schools. Adults usually are solitary dwellers of reef areas and offshore areas.

behavior

The fearsome appearance of barracudas combined with voracious feeding behavior and a notable curiosity toward divers has made them one of the most familiar families of marine fishes.

feeding ecology and diet

Voracious predators of small fishes, squid, and crustaceans.

reproductive biology

Most males mature at two years and all are mature by three years. Some females mature at three years and all are mature at four. The spawning season is from April through October off southern Florida. Females contain 500,000 to 700,000 mature eggs at one time but spawn several times in a season.

conservation status

Not threatened.

significance to humans

Unprovoked attacks on humans have been documented, but they are very rare, and most have occurred because the swimmer was carrying or wearing a silvery, bright object, which a barracuda misidentifies as prey. Human consumption of large individuals may cause ciguatera, a kind of fish poisoning. The toxicity of barracuda flesh is related to the food habits of larger barracuda, which accumulate in their flesh toxin from their prey. There is good evidence that the source of the toxin is a dinoflagellate. Barracuda are not targets of a directed fishery but are caught with hand lines, trolling gear, bottom trawls, gill nets, and trammel nets. Catch data are not reported to the FAO by species; all species of the genus are combined. Marketed fresh and salted. There is a tie for all-tackle game fish record between an 85-lb (38.5-kg) fish from Christmas Island, Kiribati, and one from the Philippines.


Largehead hairtail

Trichiurus lepturus

family

Trichiuridae

taxonomy

Trichiurus lepturus Linnaeus, 1758, South Carolina.

other common names

English: Atlantic cutlassfish; French: Poisson sabre commun; Spanish: Pez sable.

physical characteristics

Maximum length 47 in (120 cm) total length, commonly 20–39 in (50–100 cm). Body extremely elongate and strongly compressed, ribbon-like tapering to a point. No caudal fin. Eye large, contained 5–7 times in head length (head length divided by eye diameter equals 5–7). Mouth large with a cartilaginous process at tip of upper and lower jaws. Two or three pairs of enlarged fangs with barbs near tip of upper jaw and another pair near tip of lower jaw. Dorsal fin high and long, no notch between spinous and soft portions, three spines and 130–135 soft rays. Anal fin reduced to 100–105 minute spinules, usually embedded in the skin. Pectoral fins short; pelvic fins absent. Vertebrae numerous, 162–168. Fresh specimens steel blue with silvery reflection, color becoming silvery gray after death.

distribution

Tropical and temperate marine waters of the world if the eastern Pacific Trichiurus nitens is regarded as a synonym of T. lepturus Nakamura and Parin, 1993.

habitat

Benthopelagic, continental shelf to 1,148 ft (350 m), occasionally in shallow waters and at the surface at night.

behavior

Juveniles and small adults form schools about 100 m above the bottom during the daytime and form loose feeding aggregations at night-time near the surface. Large adults feed on pelagic prey near the surface during the daytime and migrate to the bottom at night.

feeding ecology and diet

Young and immature fish feed mostly on krill, small planktonic crustaceans, and small fishes. Adults become more piscivorous and feed on a wide variety of fishes plus squids and crustaceans.

reproductive biology

In the Gulf of Mexico, spawning occurs offshore at depths greater than 151 ft (46 m). The fish mature at 2 years of age and a size of approximately 12 in (30 cm) preanal length for females and 11 in (28 cm) for males. Adult females produce 33,000–85,000 eggs. Eggs are pelagic with a diameter of 0.067–0.074 in (1.7–1.9 mm) and hatch in 3–6 days.

conservation status

Not threatened.

significance to humans

An important food fish in many parts of the world. FAO catch statistics for 1991–2000 show catches of 867,145–1,631,253 tons (786,661–1,479,848 metric tons) per year by 44 countries in 11 FAO fishing areas. Caught with a variety of nets. Also taken by anglers; the all-tackle world record is an 8-lb (3.7-kg) fish taken off Rio de Janeiro.


Swordfish

Xiphias gladius

family

Xiphiidae

taxonomy

Xiphias gladius Linnaeus, 1758, European seas.

other common names

French: Espadon; Spanish: Pez espada.

physical characteristics

Reaches a maximum size of 175 in (445 cm) total length and approximately 1,190 lb (540 kg). The body is elongate and cylindrical. Two widely separated dorsal fins in adults, the first much larger than the second, the first with 34–49 rays, the second with four to six rays. Two separate anal fins in adults, the first with 12–16 rays, the second with three or four rays. Pectoral fins falcate, located low on body sides, with 17–19 rays. Caudal fin large and lunate, with a deep notch on upper and lower profiles of caudal peduncle. Fine file-like teeth and scales with small spines are present in juveniles but become embedded in the skin with growth at approximately 3 ft (1 m) in length. Left and right branchiostegal membranes separated distally. Vertebrae, 26. Back and sides of body blackish brown, gradually fading to light brown on ventral side.

distribution

Cosmopolitan in tropical, temperate, and sometimes cold waters of all oceans, including the Mediterranean, Black, and Caribbean seas.

habitat

This is an epipelagic and mesopelagic, oceanic species, usually found in surface waters warmer than 55.4°F (13°C), the optimum temperature range being 64.4–71.6°F (18–22°C). Swordfishes have been acoustically tracked and directly observed from submersibles in the western Atlantic and eastern Pacific to depths of 2,024 ft (617 m).

behavior

It is likely that swordfishes use the sword to stun or kill some prey, as shown by slashes on the bodies of squid and fishes found in swordfish stomachs. The brain and eyes of swordfish are warmer than the water in which they live. The tissue that heats the brain is developed from the superior rectus muscle of the eye. The brain heater protects the central nervous system from rapid cooling during vertical excursions of as much as 984 ft (300 m) that these fish may make through a temperature range as great as 34.2°F (19°C) in 2 hours.

feeding ecology and diet

Adult swordfishes are opportunistic feeders, known to forage for their food from the surface to the bottom over a wide depth range. Over deep water, they feed primarily on pelagic fishes including tuna, dolphinfishes, lancetfishes, flyingfishes, and pelagic squids. In shallow waters swordfishes often take neritic pelagic fishes such as mackerel, herring, anchovies, sardines, and sauries. Large adults may make feeding trips to the bottom for demersal fishes.

reproductive biology

In the western Atlantic, spawning apparently occurs throughout the year in the Caribbean, the Gulf of Mexico, and waters off Florida. Swordfishes spawn in the upper water layers at depths of 0–246 ft (0–75 m) and temperatures of approximately 73.4°F (23°C). Swordfishes first spawn at 5 or 6 years of age and 59–67 in (150–170 cm) eye-fork length and lay 2–5 million eggs.

conservation status

Listed by IUCN as Data Deficient. Populations of swordfish have been greatly reduced by fishing, particularly in the Atlantic Ocean. A consumer boycott of Atlantic swordfish organized by the United States–based Natural Resources Defense Council and Sea Web affected prices enough to gather crucial momentum toward a recovery plan for depleted swordfish in the Atlantic (Safina, 2001).

significance to humans

Appreciation of swordfish as a food fish is recent. Swordfishes brought only approximately $0.24 per pound (0.5 kg) in 1919 and $0.60 in 1946. There are important fisheries for swordfish in all three major oceans. Swordfishes are caught by long line, harpoon, drift gill net, set nets, and other fishing gear. FAO catch statistics for 1991–2000 show catches of 76–116 thousand tons (69–105 thousand metric tons) per year by 77 countries. Restrictions on the sale of swordfish containing levels of mercury greater than 0.5 ppm in Canada and the United States in the early 1970s caused collapse of the Canadian fishery and severely restricted landings in the United States. The mercury guidelines were raised to 1.0 ppm in 1979, and by 1980 catch and effort had reached a new high in the northwest Atlantic. Swordfishes are important sport fishes. The all-tackle game fish record is a 1,182-lb (536.2-kg) fish taken off Chile.


Resources

Books

Collette, B. B., C. Reeb, and B. A. Block. "Systematics of the Tunas and Mackerels (Scombridae)." In Tuna: Physiology, Ecology, and Evolution, edited by Barbara A. Block and E. Donald Stevens. Vol. 19, Fish Physiology. San Diego: Academic Press, 2001, 1–33.

Safina, C. "Tuna Conservation." In Tuna: Physiology, Ecology, and Evolution, edited by Barbara A. Block and E. Donald Stevens. Vol. 19, Fish Physiology. San Diego: Academic Press, 2001, 413–466.

Periodicals

Collette, B. B., and C. E. Nauen. "FAO Species Catalogue: Scombrids of the World: An Annotated and Illustrated Catalogue of Tunas, Mackerels, Bonitos, and Related Species Known to Date." FAO Fisheries Synopsis 2, no. 125(1983).

Collette, B. B., T. Potthoff, W. J. Richards, S. Ueyangi, J. L. Russo, and Y. Nishikawa. "Scombroidei: Development and Relationships." In American Society of Ichthyologists and Herpetologists Special Publication No. 1., edited by H. G. Moser, W. J. Richards, D. M. Cohen, M. P. Fahy, A. W Kendall Jr., and S. L. Richardson, 591–620. Lawrence, KS: Allen Press, 1984.

de Sylva, D. P. "Systematics and Life History of the Great Barracuda, Sphyraena barracuda (Walbaum)." Studies in Tropical Oceanography 1 (1963): 1–179.

Johnson, G. D. "Scombroid Phylogeny: An Alternative Hypothesis." Bulletin of Marine Science 39 (1986): 1–41.

Nakamura, I. "FAO Species Catalogue: Billfishes of the World: An Annotated and Illustrated Catalogue of Marlins, Sailfishes, Spearfishes and Swordfishes Known to Date." FAO Fisheries Synopsis 5, no. 125 (1985).

Nakamura, I., and N. V. Parin. "FAO Species Catalogue: Snake Mackerels and Cutlassfishes of the World Families Gempylidae and Trichiuridae: An Annotated and Illustrated Catalogue of the Snake Mackerels, Snoeks, Escolars, Gemfishes, Sackfishes, Domine, Oilfish, Cutlassfishes, Scabbardfishes, Hairtails and Frostfishes Known to Date." FAO Fisheries Synopsis 15, no. 125 (1993).

Regan, C. T. "On the Anatomy and Classification of the Scombroid Fishes." Annual Magazine of Natural History, Series 8 3 (1909): 66–75.

Tyler, J. C., G. D. Johnson, I. Nakamura, and B. B. Collette. "Morphology of Luvarus imperialis (Luvaridae), with a phylogenetic analysis of the Acanthuroidei (Pisces)." Smithsonian Contributions to Zoology 1989, no. 485: 1–78.

Organizations

Inter-American Tropical Tuna Commisssion. 8604 La Jolla Shores Drive, La Jolla, CA 92037-1508 USA. Phone: (858) 546-7100. Fax: (858) 546-7133. Web site: <http://www.iattc.org>

International Commission for the Conservation of Atlantic Tunas. Calle Corazón de Maria, 8, 6th floor, Madrid, E-28002 Spain.

Bruce B. Collette, PhD

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