Animal Diversity Web

Di­ver­sity

The fam­ily Scom­bri­dae, the mack­erels, tunas, and boni­tos, in­cludes some of the world’s most pop­u­lar food and sport fishes. The fam­ily also boasts the fastest-swim­ming fishes in the world, and bluefin tunas are prob­a­bly the largest of all bony fishes. Scom­brids’ size, speed, and pop­u­lar­ity are re­lated to their high de­gree of adap­ta­tion to a pelagic, no­madic ex­is­tence. Their bod­ies are formed to max­i­mize swim­ming ef­fi­ciency, and tunas even have a vas­cu­lar heat ex­change sys­tem that al­lows for pro­longed swim­ming in colder water (see Phys­i­cal De­scrip­tion). Smaller mack­erels often live closer to shore, but other mack­erels, tunas, and boni­tos roam deeper wa­ters, often in wide mi­gra­tory pat­terns (see Habi­tat). Due to their great range and ex­ten­sive use as food fish, scom­brids bear many com­mon names and have long been fa­mil­iar to hu­mans. Boni­tos, for ex­am­ple, ap­pear in Cap­tain Cook’s jour­nals. Human in­flu­ence, how­ever, has ren­dered at least five species en­dan­gered or vul­ner­a­ble to ex­tinc­tion. The fam­ily Scom­bri­dae is com­prised of two tribes, sub­di­vided into 15 gen­era and 49 species. (Helf­man, et al., 1997; John­son and Gill, 1998; Nel­son, 1994; The World Con­ser­va­tion Union, 2002; Wheeler, 1985)

Ge­o­graphic Range

Tunas, mack­erels, and boni­tos can be found world­wide in trop­i­cal and sub­trop­i­cal seas, with many species trav­el­ing pe­ri­od­i­cally into cool tem­per­ate wa­ters. (John­son and Gill, 1998; Nel­son, 1994)

• Biogeographic Regions
• nearctic
  • native
• palearctic
  • native
• oriental
  • native
• ethiopian
  • native
• neotropical
  • native
• australian
  • native
• oceanic islands
  • native
• indian ocean
  • native
• atlantic ocean
  • native
• pacific ocean
  • native
• mediterranean sea
  • native

• Other Geographic Terms
• cosmopolitan

Habi­tat

Scom­brids are, for the most part, pelagic (open-ocean) fishes liv­ing in trop­i­cal and sub­trop­i­cal seas. Some species make sea­sonal for­ays into cool tem­per­ate or cold wa­ters. Some, es­pe­cially the smaller mack­erels, re­main near coast­lines, while many oth­ers roam deeper wa­ters. They are a ma­rine fam­ily, al­though some groups occur in brack­ish water, and one nor­mally ma­rine species, Scombero­morus sinen­sis, has been found in fresh water 300 km up the Mekong River. Many groups within Scom­bri­dae tend to re­main near the sur­face and over the con­ti­nen­tal shelf. (Helf­man, et al., 1997; John­son and Gill, 1998; Nel­son, 1994; Wheeler, 1985)

• Habitat Regions
• temperate
• tropical
• saltwater or marine
• freshwater

• Aquatic Biomes
• pelagic
• coastal
• brackish water

Phys­i­cal De­scrip­tion

Scom­brids (tunas, mack­erels, and boni­tos) have stream­lined bod­ies that taper on ei­ther end, mod­er­ately large mouths, and well-de­vel­oped teeth. Gill mem­branes are not at­tached to the isth­mus. Scales are cy­cloid and usu­ally tiny, and body col­oration is metal­lic, often blue and sil­ver. Span­ish mack­erels have yel­low to bronze spots and boni­tos and tunas may have dusky bands and fins. The dor­sal fin is com­posed of nine to 27 densely packed rays, and the pelvic fins have six rays. One mem­ber of the fam­ily, bluefin tuna, can reach 4.2 m and are prob­a­bly the world’s largest bony fishes. Scom­brids are highly adapted to con­tin­u­ous swim­ming in the open ocean. Their bod­ies are an ideal stream­lined shape, with the thick­est part of the body oc­cur­ring two-fifths of the way back from the head. Their dor­sal fins can slot into grooves to re­duce drag, and the cau­dal fin is stiff and sickle-shaped for pow­er­ful propul­sion. The five to 12 sep­a­rate fin­lets be­hind the anal and sec­ond dor­sal fins may allow the tail to push against less tur­bu­lence by pre­vent­ing vor­tices from form­ing in water flow­ing to­ward the tail. The slen­der cau­dal pe­dun­cle bears at least two keels that re­duce drag and may ac­cel­er­ate water flow­ing over the tail. (Click here to see a fish di­a­gram). (Allen and Robert­son, 1994; Böhlke and Chap­lin, 1968; Helf­man, et al., 1997; John­son and Gill, 1998; Nel­son, 1994; Wheeler, 1985)

Tunas are neg­a­tively buoy­ant and must swim con­tin­u­ously to avoid sink­ing. In ad­di­tion, they re­quire con­stant move­ment to ven­ti­late the gills. Through a process called ram gill ven­ti­la­tion, swim­ming (at speeds no less than 65 cm per sec­ond) forces water over the gills. Tunas have nu­mer­ous lamel­lae (gill mem­branes) and very thin lamel­lar walls, and are able to ex­tract more oxy­gen from the water than any other fish. Tunas have large hearts and blood vol­umes. They also have a high pro­por­tion of the red mus­cle that per­mits sus­tained swim­ming, buried cen­trally along the spinal col­umn to con­serve heat. Other mem­bers of the fam­ily, such as the mack­erels, also have red mus­cle, but lo­cated nearer the out­side of the fish. (Helf­man, et al., 1997; John­son and Gill, 1998)

One of the most strik­ing fea­tures of the scom­brids is that some groups are en­dother­mic, able to main­tain a body tem­per­a­ture higher than that of the sur­round­ing water. Tunas (tribe Thun­nini) con­serve heat pro­duced by swim­ming mus­cles through an arrange­ment of blood ves­sels called a rete mirabile (“won­der­ful net”). These blood ves­sels act as a coun­ter­cur­rent heat-ex­changer. In any fish, when blood cy­cles through the gills to re­ceive oxy­gen, it also cools to the tem­per­a­ture of the sur­round­ing water. In tunas, this blood is di­verted to ves­sels near the out­side of the body in­stead of trav­el­ing di­rectly through the fish’s core. Be­fore flow­ing in­ward, the cool, oxy­genated blood passes through a net­work of small ves­sels, coun­ter­cur­rent to warm blood leav­ing the swim­ming mus­cles, and heat is trans­ferred to the en­ter­ing blood. In this way much of the heat gen­er­ated by swim­ming mus­cles is con­served. In wa­ters rang­ing from 7 to 30˚ C, bluefin tuna main­tain mus­cle tem­per­a­tures be­tween 28 and 33 C. Oth­ers keep body tem­per­a­tures 3 to 7 de­grees C warmer than the sur­round­ing water. Some species, such as big­eye tuna, uti­lize the heat ex­changer only when they enter colder water. En­dothermy also helps warm parts of the cen­tral ner­vous sys­tem, which sta­bi­lizes ner­vous sys­tem func­tion in cold water. But­ter­fly mack­erels keep brain and eye tem­per­a­tures el­e­vated using ther­mo­genic (heat-pro­duc­ing) tis­sue. (Click here to see a di­a­gram of tuna ther­moreg­u­la­tion). (Allen and Robert­son, 1994; Helf­man, et al., 1997; John­son and Gill, 1998; Moyle and Cech, 2000; Nel­son, 1994; Wheeler, 1985)

• Other Physical Features
• endothermic
• heterothermic
• bilateral symmetry

De­vel­op­ment

Car­ried by the same cur­rent sys­tem as adults, scom­brid lar­vae and ju­ve­niles grow and feed along with ma­ture in­di­vid­u­als. In at least one species, At­lantic mack­erel, eggs hatch in two to five days de­pend­ing on the tem­per­a­ture. Mack­erel grow quickly and can reach 24 cm in a year. (Helf­man, et al., 1997; Wheeler, 1985)

Re­pro­duc­tion

No in­for­ma­tion was found re­gard­ing mat­ing sys­tems in Scom­bri­dae.

Scom­brids, with the ex­cep­tion of bluefin tunas, spawn re­peat­edly. Some, like Scomber scom­brus (At­lantic mack­erel), spawn all sum­mer long. Fe­male mack­erels pro­duce, on av­er­age, about half a mil­lion eggs, which float near the sur­face. Bluefin tunas spawn in trop­i­cal wa­ters of the Gulf of Mex­ico, and spend the rest of the year feed­ing in tem­per­ate re­gions. (Helf­man, et al., 1997; Wheeler, 1985)

• Key Reproductive Features
• iteroparous
• seasonal breeding

No in­for­ma­tion was found re­gard­ing parental care in Scom­bri­dae.

Lifes­pan/Longevity

No in­for­ma­tion was found re­gard­ing lifes­pan of fishes in Scom­bri­dae.

Be­hav­ior

Most scom­brids are school­ing fishes, but some can be found singly. They fol­low a no­madic lifestyle, some­times mak­ing mi­gra­tions of huge dis­tances. For some groups, mi­gra­tions are sea­sonal and may be de­ter­mined by water tem­per­a­ture. Scom­brids are con­tin­u­ous swim­mers, and tunas in par­tic­u­lar have a unique, ef­fi­cient swim­ming style (called thun­ni­form), in which the body re­mains stiff while the thin tail os­cil­lates quickly. Some species of bonito (in the genus Sarda) ha­bit­u­ally leap clear of the water when pur­su­ing prey. (Helf­man, et al., 1997; Wheeler, 1985)

• Key Behaviors
• natatorial
• motile
• nomadic
• migratory
• social

Com­mu­ni­ca­tion and Per­cep­tion

No in­for­ma­tion was found re­gard­ing com­mu­ni­ca­tion in Scom­bri­dae.

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Scom­brids are ac­tive preda­tors that feed on a wide range of or­gan­isms. The diet of a sin­gle species may in­clude crabs, shrimps, squids, crus­taceans, the lar­vae of fishes and in­ver­te­brates, and fishes sev­eral feet long. Some smaller species strain zoo­plank­ton through their gill rak­ers. Tunas feed on a va­ri­ety of mid-wa­ter and sur­face fishes, with mack­erel pro­vid­ing a fa­vorite meal. Tunas’ abil­ity to main­tain el­e­vated body tem­per­a­tures en­ables them to swiftly pur­sue prey in the cold wa­ters of deeper depths and higher lat­i­tudes. Mi­gra­tory tunas have the fastest di­ges­tion rates and high­est meta­bolic rates of any fish. (Böhlke and Chap­lin, 1968; Froese, et al., 2003; Helf­man, et al., 1997; Wheeler, 1985)

• Primary Diet
• carnivore
  • piscivore
  • eats non-insect arthropods

Pre­da­tion

Some of the smaller species, such as Scomber japon­i­cus, are food for a large num­ber of preda­tors, from fishes and por­poises to seals and seabirds. Mack­erels are fed upon by large tunas, other large fishes, and sharks. Tunas, even large ones, must watch out for the tem­per­ate and warm tem­per­ate sword­fish Xiphias gla­d­ius and other trop­i­cal sail­fishes, spearfishes and mar­lins (Is­tio­pho­rus, Tetrap­turus, Makaira). Hu­mans are a preda­tor shared by all the scom­brids. (Helf­man, et al., 1997; Wheeler, 1985)

• Known Predators

  • tuna (Scombridae)
  • swordfishes (Xiphias)
  • spearfishes (Istiophoridae)
  • marlins (Istiophoridae)
  • sharks (Chondrichthyes)
  • porpoises (Phocoenidae)
  • seals (Phocidae)
  • seabirds (Aves)
  • humans (Homo sapiens)

Ecosys­tem Roles

Scom­brids are major preda­tors in pelagic habi­tats. As such they im­pact the pop­u­la­tions of the many or­gan­isms on which they feed, from zoo­plank­ton to fish lar­vae to large fish. They, in turn, pro­vide food for each other, large fishes, por­poises, seals, and seabirds. (Böhlke and Chap­lin, 1968; Helf­man, et al., 1997; Wheeler, 1985)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Most scom­brids (tunas, mack­erels, and boni­tos) are im­por­tant food, com­mer­cial, and sport fishes. In some parts of the world, i.e. the Mediter­ranean and Cal­i­forn­ian coasts, tunas have been fished lo­cally for many years, but heavy com­mer­cial ex­ploita­tion of open-ocean tunas has led in some cases to de­ple­tion of tuna pop­u­la­tions. Much of the tuna catch is har­vested for can­ning. Ap­par­ently the flesh of king mack­erel has oc­ca­sion­ally been toxic when eaten. (Wheeler, 1985)

• Positive Impacts
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

No spe­cific in­for­ma­tion was found con­cern­ing any neg­a­tive im­pacts to hu­mans.

Con­ser­va­tion Sta­tus

As of 1994 there were sev­eral threat­ened species in Scom­bri­dae. Scombero­morus con­color (Mon­ter­rey Span­ish mack­erel) was listed as en­dan­gered, and Thun­nus mac­coyyii (south­ern bluefin tuna) as crit­i­cally en­dan­gered; in other words both face se­vere threat of ex­tinc­tion. Thun­nus obe­sus (big­eye tuna) was listed as vul­ner­a­ble, and two oth­ers, Thun­nus alalunga (al­ba­core tuna) and Thun­nus thyn­nus (north­ern bluefin tuna) may be threat­ened as well. (The World Con­ser­va­tion Union, 2002)

• IUCN Red List [Link]

  Not Evaluated

Other Com­ments

The fos­sil record for Scom­bri­dae dates back to the lower Ter­tiary and lower Eocene. (Berg, 1958)

Con­trib­u­tors

Mon­ica Wein­heimer (au­thor), An­i­mal Di­ver­sity Web.

Ref­er­ences

Allen, G., D. Robert­son. 1994. Fishes of the Trop­i­cal East­ern Pa­cific. Hon­olulu, HI: Uni­ver­sity of Hawaii Press.

Berg, L. 1958. Sys­tem Der Rezen­ten und Fos­silen Fis­char­ti­gen und Fis­che. Berlin: VEB Deutscher Ver­lag der Wis­senschaften.

Böhlke, J., C. Chap­lin. 1968. Fishes of the Ba­hamas and Ad­ja­cent Trop­i­cal Wa­ters. Wyn­newood, PA: Pub­lished for the Acad­emy of Nat­ural Sci­ences of Philadel­phia by Liv­ingston.

Froese, R., D. Pauly, D. Wood­land. 2003. "Fish Base" (On-line). Fish­Base World Wide Web elec­tronic pub­li­ca­tion. Ac­cessed Sep­tem­ber 16, 2003 at http://​www.​fishbase.​org/​.

Helf­man, G., B. Col­lete, D. Facey. 1997. The Di­ver­sity of Fishes. Malden, MA: Black­well.

John­son, G., A. Gill. 1998. Perches and Their Al­lies. Pp. 190 in W Es­chmeyer, J Pax­ton, eds. En­cy­clo­pe­dia of Fishes – sec­ond edi­tion. San Diego, CA: Aca­d­e­mic Press.

Kuiter, R. 1993. Coastal Fishes of South-East­ern Aus­tralia. Hon­olulu, HI: Uni­ver­sity of Hawaii Press.

Moyle, P., J. Cech. 2000. Fishes: An In­tro­duc­tion to Ichthy­ol­ogy – fourth edi­tion. Upper Sad­dle River, NJ: Pren­tice-Hall.

Nel­son, J. 1994. Fishes of the World – third edi­tion. New York, NY: John Wiley and Sons.

The World Con­ser­va­tion Union, 2002. "IUCN 2002" (On-line). 2002 IUCN Red List of Threat­ened Species. Ac­cessed Sep­tem­ber 16, 2003 at http://​www.​iucnredlist.​org/​.

Wheeler, A. 1985. The World En­cy­clo­pe­dia of Fishes. Lon­don: Mac­don­ald.