Animal Diversity Web

Di­ver­sity

Genus Alop­ias con­sists of three species: Alop­ias vulpi­nus, Alop­ias su­per­cil­io­sus, and Alop­ias pelag­i­cus, all of which are re­ferred to as thresher sharks. A. vulpi­nus is the most com­mon species and is re­ferred to as com­mon thresher sharks. A. su­per­cil­ious are re­ferred to as big­eye thresher sharks. Alop­ias pelag­i­cus are re­ferred to as pelagic thresher sharks. Some other com­mon names of all three species in­clude fox sharks, sea foxes, and swiveltails. Thresher sharks be­long to fam­ily Alopi­idae, order Lam­ni­formes, and phy­lum Chon­drichthyes. These sharks are best known for the ex­ten­sion on the upper lobe of their cau­dal fins that can grow to over half their body length. Com­mon thresher sharks have fal­cate pec­toral fins that are nar­row-tipped and white patches that ex­tend from the mouth to the ab­domen around the base of the pec­toral fins. Big­eye thresher sharks are known for their large oval eyes and v-shaped ridge on their heads. They pos­sess longer snouts and fewer teeth than com­mon thresh­ers. Pelagic thresher sharks pos­sess a nar­rower head and longer snout than com­mon thresh­ers with straight pec­toral fins. (Jor­dan, 2022)

Ge­o­graphic Range

Thresher sharks are found world­wide in oceanic and coastal re­gions of trop­i­cal and tem­per­ate wa­ters. They can be found as far north as Nor­way and as far south as the bot­tom of South Amer­ica. (Jor­dan, 2022)

• Biogeographic Regions
• oriental
  • native
• ethiopian
  • native
• neotropical
  • native
• australian
  • native
• indian ocean
  • native
• atlantic ocean
  • native
• pacific ocean
  • native
• mediterranean sea
  • native

Habi­tat

Thresher sharks can be found in both coastal and oceanic water. Ju­ve­niles are most com­monly found in coastal areas, while adults are found in deep wa­ters. Thresher sharks are known to in­habit wa­ters up to 1,800 feet (550m) in depth, but they are mostly ob­served at the sur­face, breach­ing the water. Gen­er­ally, thresher sharks pre­fer cold, pelagic water. (Jor­dan, 2022)

• Habitat Regions
• temperate
• tropical
• saltwater or marine

• Aquatic Biomes
• pelagic
• coastal

Sys­tem­atic and Tax­o­nomic His­tory

Genus Alop­ias was for­merly known as Vulpec­ula, as named in 1913. The com­mon thresher shark, A. vulpi­nus, has sev­eral syn­onyms: Alop­ias vulpi­nus, Alop­ias vulpi­nus, Alop­ias vulpi­nus, and Alop­ias geryi. A. vulpi­nus got its cur­rent name from Bon­naterre in 1788. Pelagic thresher sharks (A. pelag­i­cus) have no syn­onyms and was named by Naka­mura in 1935. Big­eye thresher sharks (A. su­per­cil­io­sus) also have no syn­onyms and was named by Lowe in 1841. (Eit­ner, 1995)

• Synonyms

  • Vulpecula
  • Alopias vulpinus
  • Alopias vulpinus
  • Alopias vulpinus
  • Alopias geryi

Phys­i­cal De­scrip­tion

All three species of thresher sharks ex­press coun­ter­shad­ing, being blue/gray on the dor­sal side and white on the ven­tral side. The dor­sal, pec­toral, pelvic, and cau­dal fins are all dark blue/gray on the dor­sal side. All thresher sharks have short­ened heads with cone-shaped snouts and small mouths. The dis­tinc­tively long, upper cau­dal fin lobe of thresher sharks make up al­most half the body length of all three species. Com­mon thresh­ers can grow up to 20ft long, while big­eye and pelagic thresh­ers can reach up to 16ft. In all three species, fe­males are longer than males. Big­eye thresh­ers are known for their large oval eyes. They have fewer teeth than com­mon thresh­ers, a longer snout, and a v-shaped ridge on their head. Pelagic thresh­ers have nar­rower heads and more elon­gated snouts than com­mon thresh­ers. (Jor­dan, 2022; Seitz, 2021)

• Other Physical Features
• ectothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

De­vel­op­ment

Com­mon thresher sharks de­velop ear­lier than other Alop­ias species. Males are sex­u­ally ma­ture when they are 3-6 years old, while fe­males sex­u­ally ma­ture when they are 4-5 years old. In com­par­i­son, big­eye thresher sharks and pelagic thresher sharks reach sex­ual ma­tu­rity much later, around 10-13 years old. (Drew, et al., 2015; "Pelagic Thresher Shark", 2014)

• Development - Life Cycle
• temperature sex determination

Re­pro­duc­tion

Com­mon thresher sharks mate in late sum­mer and are ovo­vi­vip­a­rous. Com­mon thresh­ers have a ges­ta­tion pe­riod of 9 months and have 4-6 pups. Big­eye thresh­ers have lit­ters of 2-4 pups each year. Pelagic thresher sharks have an­nual lit­ters of around 2 pups. (Drew, et al., 2015; "Pelagic Thresher Shark", 2014)

• Mating System
• polygynous

Chon­drichthyes males pos­sess mod­i­fied pelvic fins called claspers which they use while mat­ing. Males grab fe­males, hold­ing onto them with their mouths while using the claspers to as­sist with in­ter­nal fer­til­iza­tion. (Pough and Janis, 2019)

• Key Reproductive Features
• sexual
• fertilization
  • internal
• ovoviviparous

Thresher sharks are ovo­vi­vip­a­rous, mean­ing eggs are fer­til­ized, de­vel­oped, and hatched within the fe­male. The fe­male then gives birth to live pups. There is no parental in­vest­ment after pups are born, but the mother must pro­vide some nu­tri­ents for hatched pups be­fore they are born. (Drew, et al., 2015; Pough and Janis, 2019)

• Parental Investment
• no parental involvement
• pre-hatching/birth
  • provisioning
    • female

Lifes­pan/Longevity

In the wild, com­mon thresh­ers can live any­where be­tween 19-50 years; big­eye thresh­ers can live up to 20 years; pelagic thresh­ers can live up to 16 years, with some fe­males being known to live up to 28 years. (Jor­dan, 2022; Seitz, 2021)

Be­hav­ior

Thresher sharks are mainly soli­tary and all three species of thresher sharks are highly mi­gra­tory, with the com­mon thresher being cir­cum­global. Com­mon thresh­ers have a high tol­er­ance for cold wa­ters, and big­eye and pelagic thresh­ers are found in trop­i­cal and tem­per­ate wa­ters. Thresher sharks are thought to use the long upper lobe of their cau­dal fin to stun prey when hunt­ing and mostly feed on school­ing fish. When hunt­ing schools of fish, thresh­ers often work in groups or pairs. All three species are di­ur­nal, mean­ing they hunt dur­ing the day. Thresher sharks mate via in­ter­nal fer­til­iza­tion, wherein males in­sert a clasper into the fe­male’s cloaca. Thresher sharks are be­lieved to mate through­out their ranges an­nu­ally. (Car­tamil, et al., 2010; Jor­dan, 2022; Natan­son and Gervelis, 2013; Seitz, 2021)

• Key Behaviors
• natatorial
• diurnal
• motile
• migratory
• solitary

Com­mu­ni­ca­tion and Per­cep­tion

All Chon­drichthyes species have highly de­rived sen­sory or­gans, using chemore­cep­tion, mechanore­cep­tion, vi­sion, and elec­trore­cep­tion to sense prey. Chemore­cep­tion is used to pick up chem­i­cals in the water. Mechanore­cep­tion gives thresher sharks the abil­ity to pick up vi­bra­tions through the neu­ro­mast cells in their lat­eral line sys­tem. The sharks' elec­trore­cep­tion tech­niques uti­lize their am­pul­lae of Loren­zini to de­tect elec­tri­cal sig­nals in the water, such as heart­beats and mus­cle con­trac­tions of prey. (Pough and Janis, 2019)

• Perception Channels
• visual
• vibrations
• chemical
• electric

Food Habits

All three Alop­ias species use their elon­gated upper cau­dal fin lobes to stun prey when feed­ing. Chon­drichthyes pos­sess upper jaws that can pro­tract and re­tract as they open and close their mouths when feed­ing. Alop­ias species feed mostly on small school­ing species of bony fish, in­clud­ing her­rings and mack­erels. They are also known to feed on squid. (Pough and Janis, 2019; Seitz, 2021)

• Primary Diet
• carnivore
  • piscivore

Pre­da­tion

Adult Alop­ias species have no known preda­tors; how­ever, top preda­tors such as larger sharks and killer whales have been known to prey upon ju­ve­niles. (Jor­dan, 2022; Seitz, 2021)

• Known Predators

  • Large sharks
  • Toothed whales

Ecosys­tem Roles

As top preda­tors, Alop­ias species in­flu­ence the ecosys­tem by keep­ing pop­u­la­tions of prey species in check. With­out preda­tors, fish species pop­u­la­tion could boom, caus­ing top-down trophic ef­fects that can neg­a­tively in­flu­ence the en­tire ecosys­tem.

Some species of cope­pods are par­a­sites to thresher sharks, at­tach­ing them­selves to gill fil­a­ments, caus­ing dam­age and res­pi­ra­tion is­sues. (Jor­dan, 2022; Seitz, 2021)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

The In­ter­na­tional Game Fish As­so­ci­a­tion con­sid­ers all three species of thresher sharks to be game fish, mak­ing them a tar­get species for an­glers and an eco­tourism asset. The At­lantic com­mon thresher shark fish­ery in the U.S. is man­aged by NOAA Fish­eries and the At­lantic Highly Mi­gra­tory Species Di­vi­sion. Ac­cord­ing to NOAA Fish­eries, com­mer­cial land­ings of the At­lantic com­mon thresher sharks to­taled 85,600lbs (val­ued at $38,000) in 2019. In other parts of the world, thresher sharks are caught for their fins, meat, liver, and skin. Thresher sharks also bring in eco­tourism in­come through shark swim­ming, snor­kel­ing, and scuba div­ing op­por­tu­ni­ties. (Jor­dan, 2022; Seitz, 2021)

• Positive Impacts
• body parts are source of valuable material
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no ad­verse ef­fects of Alop­ias species on hu­mans. (Jor­dan, 2022; Seitz, 2021)

Con­ser­va­tion Sta­tus

The IUCN Red List lists big­eye thresh­ers and com­mon thresh­ers as Vul­ner­a­ble and pelagic thresh­ers as En­dan­gered. All three species are caught as tar­get and by­catch species in pelagic and com­mer­cial fish­eries. The glob­ally es­ti­mated pop­u­la­tion of big­eye thresh­ers and com­mon thresh­ers has de­creased by 30-49%, and pelagic thresher pop­u­la­tions have de­creased by 50-79% over the last three gen­er­a­tions. The U.S. fish­eries that cap­ture fresher sharks have set cap­ture lim­its to help con­ser­va­tion ef­forts of these species. (Rigby, et al., 2019a; Rigby, et al., 2019b; Rigby, et al., 2019c)

• IUCN Red List [Link]

  Not Evaluated

Other Com­ments

Thresher sharks are often re­ferred to as sea foxes, pos­si­bly due to their cun­ning na­ture.

Con­trib­u­tors

Jor­dyn Pol­lock (au­thor), Col­orado State Uni­ver­sity, Syd­ney Collins (ed­i­tor), Col­orado State Uni­ver­sity.

Ref­er­ences

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2021. "Big­eye Thresher Sharks" (On-line). MarineBio. Ac­cessed Feb­ru­ary 17, 2022 at https://​www.​marinebio.​org/​species/​bigeye-thresher-sharks/​alopias-superciliosus/​.

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Seitz, J. 2021. "Alop­ias pelag­ius" (On-line). Florida Mu­seum. Ac­cessed Feb­ru­ary 17, 2022 at https://​www.​floridamuseum.​ufl.​edu/​discover-fish/​species-profiles/​alopias-pelagicus/​.