mackerel shark

n.
Any of various sharks of the family Lamnidae, including the great white shark, mako, and porbeagle, having a pointed snout, a nearly symmetrical tail, and a reputation for aggressiveness.

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(Mackerel sharks)

Class: Chondrichthyes

Order: Lamniformes

Number of families: 7

Evolution and systematics

Living lamniform sharks are mere remnants of a much greater lamniform lineage that has, for the most part, become extinct. The 15 surviving species pale in comparison to the countless hundreds that have been described from fossil remains; the genus Carcharodon alone is known from some 10 fossil species, in contrast to the single extant Carcharodon carcharias. However, the overwhelming majority of these fossils consist of isolated teeth, first appearing in the fossil record during the early Cretaceous period some 120 million years ago (mya). Fossil lamniform teeth are known from many widespread marine localities from all continents, and they resemble those of living mackerel sharks in usually being slender, with very sharp cusps and arched roots. Many living lamniform species have closely related fossil relatives, again known only from teeth, going back at least to the Paleocene epoch (some 62 mya). Some of these fossil species are even placed in genera that are still extant (e.g., Carcharodon, Odontaspis), corroborating that lamniform sharks have a remarkably long evolutionary history, as do most living shark groups.

Fossil lamniforms known from more complete remains are extremely rare and include preserved partial skeletons of goblin sharks (Mitsukurinidae) from Lebanon (about 90 million years old), and vertebrae of various taxa, such as the megalodon shark from Europe (of Miocene to Pliocene age, some 16 to 2.6 mya). The late Cretaceous goblin shark (Scapanorhynchus lewisi) is similar to the living goblin species (Mitsukurina owstoni) in having a very elongated snout, but it differs in having a much longer anal fin and more angular dorsal fins. Moreover, some features of its teeth and denticles differ as well. The megalodon shark (Carcharodon megalodon) is the most notorious fossil lamniform. It is known from huge, triangular teeth (as large as 7.9 in [20 cm] in height), that are very similar to teeth of the living white shark (Carcharodon carcharias). The megalodon shark, however, was much larger (estimated to reach up to 49 ft [15m] in length), some three times the size of the living white, and was one of the greatest marine predators of all time (and the greatest macropredatory shark). Reconstructions of its jaws, believed to have been able to fit several people when agape, feature in many museum exhibits. Megalodon fossils are known from North and South America, the Caribbean, Europe, Australasia, Japan, and Africa.

Among living elasmobranchs (sharks and rays), lamniform sharks are more closely related to the ground sharks (Carcharhiniformes), bullhead sharks (Heterodontiformes), and carpet sharks (Orectolobiformes). These four orders, united in the larger group Galeomorphii, share various evolutionary innovations, such as the unique placement of the hyomandibula (a cartilage supporting the jaws posteriorly) on the skull. Within this group, lamniforms are most closely related to the ground sharks, as both orders share a tripodal rostrum supporting the snout internally.

Living lamniforms are among the most intensely studied and best-known sharks. Four of the living species were described in the eighteenth century, five in the nineteenth, and six in the twentieth century. (The last species described was the megamouth shark in 1983.) They are currently divided into seven families, 10 genera, and 15 species, and they were first recognized as a unique group by American ichthyologist David Starr Jordan (1851–1931) in 1923.

Phylogenetic (evolutionary) relationships among lamniform genera also have received much recent attention. The goblin shark (Mitsukurina) is considered the most basal, or primitive, living lamniform, followed by the sand tiger sharks (family Odontaspididae) and the crocodile shark (Pseudocarcharias). The remaining mackerel sharks have plesodic pectoral fin skeletons, in which the internal supports extend to the distal fin margin. Recent phylogenetic theories also support a common ancestry for a lamniform subgroup—comprising the basking shark and lamnids—with lunate caudal fins. Phylogenetic studies based exclusively on characters from the teeth disagree to some extent with those based on the skeleton, but teeth can often be misleading as indicators of evolutionary relationships in sharks and rays. Molecular phylogenies are also partly at odds with morphological ones, indicating that the evolutionary history of many lamniform genera is still in dispute.

Physical characteristics

Mackerel sharks are moderate to very large, ranging from about 3.3 ft (1 m) to 49 ft (15 m) in length. Some mackerel sharks, such as the great white and shortfin mako, are among the most popularly known and easily recognizable of all sharks. Other mackerel sharks are among the most bizarre and anatomically unique sharks, such as the megamouth, goblin, and thresher sharks. Lamniform sharks have unique teeth and intestines with a ring valve (with numerous, closely stacked turns).

There is some variation among lamniform species in relation to body and fin profiles, but all mackerel sharks have two dorsal fins (usually the first dorsal fin is very tall, while the second is reduced in height), large pectoral fins (except in the goblin and crocodile sharks, and to a lesser degree in the sand tiger sharks), and a small anal fin (except in the goblin and sand tiger sharks). The caudal fin is lunate or semilunate (i.e., with a well developed lower lobe) and upright in some species (basking shark and lamnids). Thresher sharks have caudal fins about equal to the length of the body, and goblin, sand tiger, megamouth, and crocodile sharks have caudal fins with relatively small lower lobes. The snout is conical in most species (except in the megamouth shark), and paddle shaped in the goblin shark; internally the snout is supported by a tripodal rostrum, usually composed of three cartilaginous segments. The spiracles are extremely reduced. The eyes are black and round in most species and lack nictitating (protective) membranes. Five pairs of gill openings are present. Denticles along the body are very small and do not form larger spines.

Some lamniform species, particularly those of the family Lamnidae (white, porbeagle, salmon, and mako sharks) are capable of maintaining slightly elevated body temperatures in relation to the surrounding water. This is accomplished in a manner similar to tunas and mackerels (bony fishes of the family Scombridae), through a counter-current, vascular heat-exchange system. The body musculature, viscera, brains, and eyes remain at temperatures from 5.4°F (3°C) to 25.2°F (14°C) warmer than ambient water. This physiological mechanism enables lamnid mackerel sharks to maintain higher metabolic rates; hence they are capable of great bursts of activity.

Lamniforms are usually blue or blue-gray on their dorsal and lateral sides, but white to off-white ventrally. Well-defined spots and blotches are mostly absent, but the white shark has black ventral pectoral fin extremities, and some species may have whitish blotches on the tail; the salmon shark, Lamna ditropis, has brown blotches on its lateral and ventral aspects.

Distribution

Mackerel sharks are found worldwide in tropical and temperate marine waters. Some species penetrate boreal and subantarctic seas (basking shark and species of the genus Lamna), and other species are extremely wide-ranging, such as the shortfin mako and white shark. All species are somewhat widespread.

Habitat

Mackerel sharks are present in shallow, coastal waters, as well as epipelagically and mesopelagically in deeper oceanic waters. Most species, such as the mako, white, and sand tiger sharks, occur predominantly in shallow areas, while others are demersal inhabitants of continental slope regions (e.g., the goblin shark).

Behavior

The behavior of sharks that inhabit oceanic realms is generally not well known. Lamniform sharks, however, display different behaviors in relation to feeding (from filter feeding to predation), as well as in relation to metabolism. The more active species are laeterothermic (slightly warm-blooded); as a result they can swim at astounding speeds and are capable of great bursts of energy. The filter-feeding species, however, are relatively sluggish. Many species of lamniforms are known to leap completely out of the water (breaching), and not only as a result of being hooked on a line. The reasons behind this behavior are largely unknown but may have to do with escaping predators, snatching prey (as in the white shark), or ridding themselves of parasites. A lunate caudal fin may facilitate the strong upward swimming necessary to breach the water surface. Segregation by sex and size has been recorded in lamniform sharks, but much is yet to be learned about their population dynamics. More specific behavioral patterns have been described for particular species in the species accounts below.

Feeding ecology and diet

Almost all mackerel sharks are predaceous, extremely active eaters, feeding mostly on fishes belonging to numerous families (both bony fishes as well as sharks and rays), but also consuming large amounts of invertebrates (e.g., squids, octopi, gastropods, crustaceans) as well as marine mammals (pinnipeds, dolphins, and whales, as well as whale carcasses), marine turtles, and even oceanic birds. In contrast, two species, the megamouth and basking sharks, feed almost exclusively on zooplankton, and current evolutionary theories indicate that filter feeding evolved independently in both species, which also differ in their mode of filter feeding. Lamniform sharks are preyed upon by other shark species, including their own species.

Reproductive biology

As far as is known, all species of mackerel sharks are yolk-sac viviparous (ovoviviparous, aplacentally viviparous); i.e., they give birth to live young that develop in utero and that feed on the yolk contents of their yolk sacs. But in many lamniform species, intrauterine cannibalism has been confirmed or is suspected. This occurs when embryos prey on each other (adelphophagy) or on other eggs (oophagy) inside the uterus after their yolk reserves are depleted. This group is the only elasmobranch taxon in which this occurs. Adelphophagy is known for certain in only one species, Carcharias taurus, but is suspected in others. Gestation periods vary among species and are comparatively poorly known. In some species, females are gravid from eight months to one year, while other species have longer gestations (up to 18 months). A period of reproductive inactivity may follow a gestation. Courtship patterns are presumably similar to those in many other sharks, with males biting females to subdue them prior to copulation and also during copulation.

Conservation status

The following species are listed by the IUCN: Alopias vulpinus, Lamna ditropis, Megachasma pelagios, and Odontaspis noronhai (as Data Deficient); Carcharodon carcharias, Carcharias taurus, and Cetorhinus maximus (as Vulnerable); Lamna nasus, Isurus oxyrinchus, and Pseudocarcharias kamoharai (as Lower Risk/Near Threatened).

Significance to humans

Many lamniform species are captured on longlines or trawls, either as bycatch or as specific targets, by the commercial fishing industry. The flesh is consumed fresh, frozen, smoked, or dried-salted, and their fins are procured by the destructive shark fin soup industry. Sport fishing for makos and other lamniforms is also common. This order contains what has been considered to be the most dangerous shark species, the white shark. But the misguided, anthropocentric perception that the white shark and other lamniform species are potential "man-eaters" has faded in the past decade; this negative image was given to this species mostly by sensationalistic media. Ironically, the roles are presently reversed, as it is now well understood that it is the sharks that are the victims of humankind, mostly through overfishing and the ruthless, cruel, shark fin soup fad, and not the other way around. In fact, many species of lamniforms and other sharks are quite valuable alive. The sand tiger shark is important as an exhibition fish in public aquaria, where it is relatively easily kept for long periods. Many lamniforms, such as the sand tiger, white, thresher, basking, and mako sharks, are even common ecotourist attractions in many places around the world.

Species accounts

Thresher shark
Basking shark
White shark
Shortfin mako
Porbeagle
Megamouth shark
Goblin shark
Sand tiger shark
Crocodile shark

Resources

Books:

Applegate, S. P., and L. Espinosa-Arrubarrena. "The Fossil History of Carcharodon and Its Possible Ancestor, Cretolamna: A Study in Tooth Identification." In Great White Sharks: The Biology of Carcharodon carcharias, edited by A. P. Klimley and David G. Ainley, 19–36. San Diego, CA: Academic Press, 1996.

Bigelow, Henry B., and William C. Schroeder. "Sharks." In Fishes of the Western North Atlantic, Vol. 1, pt. 1 of Memoir of the Sears Foundation for Marine Research, 59–576. New Haven, CT: Yale University, 1948.

Branstetter, Steven, ed. Conservation Biology of Elasmobranchs. NOAA Technical Report, NMFS 115. Seattle, WA: U. S. Department of Commerce, 1993.

Burgess, G. H., and M. Callahan. "Worldwide Patterns of White Shark Attacks on Humans." In Great White Sharks: The Biology of Carcharodon carcharias, edited by A. Peter Klimley and David G. Ainley, 457–469. San Diego, CA: Academic Press, 1996.

Cappetta, Henri. Chondrichthyes II, Mesozoic and Cenozoic Elasmobranchii. Stuttgart, Germany: Gustav Fischer Verlag, 1987.

Carwardine, Mark, and Ken Watterson. The Shark Watcher's Handbook: A Guide to Sharks and Where to See Them. Princeton, NJ: Princeton University Press, 2002.

Compagno, Leonard J. V. "Relationships of the Megamouth Shark, Megachasma pelagios (Lamniformes: Megachasmidae), with Comments on Its Feeding Habits." In Elasmobranchs as Living Resources: Advances in the Biology, Ecology, Systematics, and the Status of the Fisheries, 357–379, edited by H. L. Pratt, Jr., S. H. Gruber, and T. Taniuchi. NOAA Technical Report, NMFS 90. Seattle, WA: U.S. Department of Commerce, 1990. ——. Bullhead, Mackerel and Carpet Sharks (Heterodontiformes, Lamniformes and Orectolobiformes), Vol. 2 of Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome, Italy: Food and Agriculture Organization of the United Nations, 2001.

Compagno, Leonard J. V., and V. H. Niem. "Families Odontaspididae, Pseudocarchariidae, Alopiidae, and Lamnidae." In Western Central Pacific Identification Sheets to Species, edited by Kent E. Carpenter and Volker H. Niem, 1264–1278. Rome, Italy: Food and Agriculture Organization of the United Nations, 1999.

Demski, Leo S., and John P. Wourms, eds. Reproduction and Development of Sharks, Skates, Rays and Ratfishes. Boston, MA: Kluwer Academic Publishers, 1993.

Ellis, Richard, and John E. McCosker. Great White Shark. New York: Harper Collins, 1991.

Francis, M. P. "Observations on a Pregnant White Shark with a Review of Reproductive Biology." In Great White Sharks:The Biology of Carcharodon carcharias, edited by A. Peter Klimley and David G. Ainley, 157–172. San Diego, CA: Academic Press, 1996.

Gottfried, M. D., Leonard J. V. Compagno, and S. C. Bowman. "Size and Skeletal Anatomy of the Giant 'Megatooth' Shark Carcharodon megalodon." In Great White Sharks: The Biology of Carcharodon carcharias, edited by A. Peter Klimley and David G. Ainley, 55–66. San Diego, CA: Academic Press, 1996.

Hamlett, William C., ed. Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes. Baltimore, MD: Johns Hopkins University Press, 1999.

Hennemann, R. M. Sharks and Rays, Elasmobranch Guide of the World. Frankfurt, Germany: Ikan, 2001.

Klimley, A. Peter, and David G. Ainley, eds. Great White Sharks: The Biology of Carcharodon carcharias. San Diego, CA: Academic Press, 1996.

Last, P. R., and J. D. Stevens. Sharks and Rays of Australia. Melbourne, Australia: CSIRO Division of Fisheries, 1994.

Naylor, G. J. P., et al. "Interrelationships of Lamniform Sharks: Testing Phylogenetic Hypotheses with Sequence Data." In Molecular Systematics of Fishes, edited by Thomas D. Kocher and Carol A. Stepien, 199–218. San Diego, CA: Academic Press, 1997.

Nelson, J. Fishes of the World. 3rd ed. New York: John Wiley & Sons, 1994.

Perrine, Doug. Sharks & Rays of the World. Stillwater, MN: Voyageur Press, 1999.

Pratt, H. L. Jr., S. H. Gruber, and T. Taniuchi, eds. Elasmobranchs as Living Resources: Advances in the Biology, Ecology, Systematics, and the Status of the Fisheries. NOAA Technical Report, NMFS 90. Seattle: U. S. Department of Commerce, 1990.

Sibley, G., J. A. Seigel and C. C. Swift, eds. Biology of the White Shark, Vol. 9 of Memoirs of the Southern California Academy of Sciences. Los Angeles: 1985.

Springer, Victor G., and Joy P. Gold. Sharks in Question. The Smithsonian Answer Book. Washington, DC: Smithsonian Institution Press, 1989.

Stillwell, C. "The Ravenous Mako." In Discovering Sharks, edited by S. H. Gruber, 77–78. Highlands, NJ: American Littoral Society, 1990.

Whitley, G. P. The Sharks, Rays, Devil-fish, and Other Primitive Fishes of Australia and New Zealand. Pt. 1 of The Fishes of Australia. Sydney, Australia: Royal Zoological Society of New South Wales, 1940.

Yano, K., J. F. Morrissey, Y. Yabumoto, and K. Nakaya, eds. Biology of the Megamouth Shark. Tokyo, Japan: Tokai University Press, 1997.

Periodicals:

Carey, F. G., et al. "Temperature, Heat Production, and Heat Exchange in Lamnid Sharks." Memoirs of the Southern California Academy of Sciences 9 (1985): 92–108.

Carey, F. G., et al. "The White Shark, Carcharodon carcharias, Is Warm-Bodied." Copeia 2 (1982): 254–260.

Eitner, B. J. "Systematics of the Genus Alopias (Lamniformes: Alopidae) with Evidence for the Existence of an Unrecognized Species." Copeia 3 (1995): 562–571.

Gilmore, R. G. "Reproductive Biology of Lamnoid Sharks." Environmental Biology of Fishes 38 (1993): 95–114.

Gilmore, R. G., J. W. Dodrill, and P. A. Linley. "Reproduction and Embryonic Development of the Sand Tiger Shark, Odontaspis taurus (Rafinesque)." Fishery Bulletin 81 (1983): 201–225.

Gruber, S. H., and Leonard J. V. Compagno. "Taxonomic Status and Biology of the Bigeye Thresher, Alopias superciliosus." Fishery Bulletin 79, no. 4 (1981): 617–640.

Hutchins, B. "Megamouth: Gentle Giant of the Deep." Australian Natural History 23, no. 12 (1992): 910–917.

Jordan, D. S. "A Classification of Fishes Including Families and Genera as far as Known." Stanford University Publications: Biological Sciences 3 (1923): 77–243.

Klimley, A. P. "The Areal Distribution and Autoecology of the White Shark, Carcharodon carcharias, off the West Coast of North America." Memoirs of the Southern California Academy of Sciences 9 (1985): 15–40. ——. "The Predatory Behavior of the White Shark." American Scientist 82, no. 2 (1994): 122–133.

Maisey, J. G. "Relationships of the Megamouth Shark, Megachasma." Copeia 1 (1985): 228–231.

Matthews, L. H. "Reproduction in the Basking Shark, Cetorhinus maximus." Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 234 (1950): 247–316.

McCosker, J. E. "White Shark Attack Behavior: Observations of and Speculations About Predator and Prey Strategies." Memoirs of the Southern California Academy of Sciences 9(1985): 123–135. ——. "The White Shark, Carcharodon carcharias, Has a Warm Stomach." Copeia 1 (1987): 195–197.

Taylor, L. R., Leonard J. V. Compagno, and P. J. Strusaker. "Megamouth—A New Species, Genus, and Family of Lamnoid Shark (Megachasma pelagios, Megachasmidae) from the Hawaiian Islands." Proceedings of the California Academy of Sciences 43 (1983): 87–110.

Tricas, T. C., and J. E. McCosker. "Predatory Behavior of the White Shark (Carcharodon carcharias), with Notes on Its Biology." Proceedings of the California Academy of Sciences 43(1984): 221–238.

Wourms, J. P. "Reproduction and Development in Chondrichthyan Fishes." American Zoologist 17 (1977): 379–410.

Organizations:

American Elasmobranch Society, Florida Museum of Natural History. Gainesville, FL 32611 USA. Web site:

[Article by: Marcelo Carvalho, PhD]

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The noun has one meaning:

Meaning #1: fierce pelagic and oceanic sharks

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