Thresher Sharks: Characteristics, Behavior, Feeding

Home | Category: Shark Species


Common thresher

Thresher sharks (Alopias species) are also known as sea foxes, swingletail sharks; swivetail sharks, whiptail sharks, thintail sharks and thrashers. They are known for their “long, scythe-like tails that account for half their body length,” according to Shark Advocates International and are “aggressive predators” that use their tail to hit and stun fish species, knocking them out before taking a bite, according to NOAA Fisheries. They are more commonly seen iin the Northern Hemisphere than the Southern Hemisphere. [Source: Irene Wright, Miami Herald, March 18, 2023]

Thresher sharks have a uniquely-shaped upper lobe on their tail that makes them unique and interesting-looking. Found in temperate and tropical oceans worldwide, they sharks use their enlarged caudal fin to herd schools of fish into tightly packed balls so they are easy attack. Threshers also use their tails for defense. Fishermen stand well clear of threshers when they are brought on board a boat. One man who got too close was decapitated with one swipe of the tail.

There are three thresher shark species. The common thresher (Scientific name: Alopias vulpinus) is by far the largest of the three species. The bigeye thresher (Alopias superciliosus) is next in size, reaching a length of 4.9 meters (16 feet); the pelagic thresher (Alopias pelagicus) is the smallest at just three meters (10 feet). The three species can be roughly distinguished by the primary color of the dorsal surface of the body. Common threshers are dark green, bigeye threshers are brown and pelagic threshers are generally blue. Lighting conditions and water clarity can affect how any one shark appears to an observer, but the color test is generally supported when other features are examined. With the exception of the bigeye thresher, thresher sharks have relatively small eyes positioned to the forward of the head.

Websites and Resources: Shark Foundation ; International Shark Attack Files, Florida Museum of Natural History, University of Florida ; Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal

Thresher Shark Habitat and Where They Are Found

Range of the common thresher: dark blue -- confirmed; light blue -- likely

Common thresher sharks are widely distributed in tropical and temperate waters in almost every major ocean. They mainly live in the open ocean far from land but sometimes approach coastal areas. They are typically found at depths of around 110 meters (360.89 feet) but have been recorded at a depth of 217 meters (712 feet). When they are found close to shore it is in areas rich with plankton, where their prey are also abundant.. [Source: NOAA, John Lewis, Animal Diversity Web (ADW) /=]

Common thresher sharks are found along the coast of North America from Maine to Florida in the Atlantic Ocean. And from Oregon to Mexico in the Pacific Ocean. They are commonly seen around Asia and occasionally in the central and western Pacific Ocean. Although little is known about their migration patterns, fishing records suggest that they move north, away from the equator, during summer months and that they move south, toward the equator, during winter months.

Common thresher sharks primarily live in temperate waters beyond the continental shelf and do not stray much more than 30 kilometers from the coast. During the day, they stay near the edge of the continental shelf at an average depth of 110 meters. Common thresher sharks have been documented diving to depths over 200 meters below the surface, though this is uncommon. At night, these sharks spend most of their time at a mid-range depths, remaining near or on the continental shelf.

Thresher Shark Characteristics

Thresher Shark at Monad Shoal, Philippines

Thresher sharks range in length from 1.6 to six meters (5.2 to 19.7feet), with their average length being 2.74 meters (9 feet). Up to 50 percent of the shark’s length is due to the characteristic enlarged upper lobe of its caudal fin. They reach weights over 500 kilograms (1,100 pounds), with their average weight being 348 kilograms (766.5 pounds). Both sexes are roughly equal in size and look similar. According to the International Game Fish Association the largest thresher shark ever caught weighed 348 kilograms (767 pounds) and was taken in the Bay of Islands, New Zealand in 1983. [Source: John Lewis, Animal Diversity Web (ADW) /=]

Thresher sharks are brown, gray, blue-gray, or blackish on the back and underside of their snout. They are lighter on the sides, and fully white below. Fins are blackish, and some have white dots on the tips. Their tail fin is sickle-shaped, and the upper part is very long, about half the length of the body. [Source: NOAA]

Common thresher sharks are the largest of the thresher species. Thresher sharks are fairly slender, with small dorsal fins and large, recurved pectoral fins, They have short heads and cone-shaped noses. Their mouth is generally small, and the teeth range in size from small to large. According to Animal Diversity Web: Unlike other threshers, they have "erect and narrow cusps" on their teeth. Like other species of threshers, common threshers have relatively small eyes near the front of the head. Common thresher shaks can be identified by their dark green dorsal fin; in other similar species, dorsal fins are blue to purple. Like many sharks, they are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them).

The average lifespan of common thresher sharks in the wild is estimated to e 25 years. Some may live up to 50. The largest common thresher shark ever recorded was 4.75 meters (15.6 feet) long and 510 kilograms (1125 pounds. Using the growth coefficient of common thresher sharks, this shark was estimated to be 43 years old. The number of common thresher sharks declined by 62 percent between 1985 and 2020. [Source: Mónica Serrano and Sean McNaughton, National Geographic, July 15, 2021; Animal Diversity Web (ADW) /=]

Thresher Shark Behavior

Common thresher sharks are generally solitary, motile (move around as opposed to being stationary) and migratory (make seasonal movements between regions, such as between breeding and wintering grounds). They communicate with vision and electric signals and sense using vision, touch, electric signals, magnetism and chemicals usually detected with smelling or smelling-like senses. Thresher sharks are one of the few shark that breach — jump fully out of the water. They do this using their elongated tail to propel them out of the water, and make turns like dolphins.

Adults tend to stay in deep water but juveniles sometimes approach close to shore. There are few known predators of common thresher sharks other than humans, orcas and large sharks such as makos. Reef sharks and even other thresher sharks sometimes eat juvenile common threshers. Pups usually stay in shallow nursery areas that are separate from adults as defense from predators. Adults are sometimes accompanied by pilot fish. Common thresher sharks are often used as bio-indicators of pollutants due to their diet and near-shore habitat.

Thresher sharks display daily vertical migration — moving to shallower waters at night and to deeper waters during the day but there is no evidence that claim or defend territories. Because they are migratory, common threshers are considered to be free-range predators. Little is known about their exact migratory routes, other than that in the Northern Hemisphere they move southward to warmer waters during the winter and northward to cooler waters during the summer.

Thresher Shark Food, Hunting and Eating Behavior

Common threshers eat a variety of fish and sea creatures, including sardines, mackerel, hake, different species of anchovies, bluefish, juvenile tuna, cuttlefish and squid and red crab from deep waters. In warmer waters, they feed primarily on anchovies, but in cooler waters they feed mostly on squid and sardines. They are known to follow mackerel into shallow waters.

Thresher shark jumping

Thresher sharks use their long tails to form fish into tight schools and then swat them and stuns them with the sharks’ long tail so the fish can be picked off and eaten. Sometimes threshers form single-sex groups. Thresher sharks sometimes hunt cooperatively, using their huge elongated tails to corral bluefish, tuna and mackerel and slap them out of the water to stun them.

Because thresher shark have poor vision, they often rely on other senses to detect prey.Their lateral line— a narrow strip of sensory cells runs along the sides of the body and into the head. — detects vibrations in the surrounding waters. According to Animal Diversity Web: This aides in locating prey from great distances, as vibrations travel well in water. Common threshers also have a strong sense of smell, and chemicals can be detected in low concentrations. Upon finding a potential meal, most threshers will bump the object with their nose or take a small test bite to determine if the object is edible before committing to a full strike. Common thresher sharks also use electromagnetic senses to perceive their environment and hunt prey. They use sensory organs clustered in their nose and head to sense impulses in the water from injured and dying fish./=\

Thresher sharks populations in the Indian Ocean occupy different depths and space according to sex. The species that occasionally hunt in a group usually do so in twos or threes.. When hunting schooling fish, thresher sharks are known to "whip" the water. Sometimes thresher sharks slice fish in half with their half before eating it.

Thresher Shark Mating, Reproduction and Offspring

Thresher sharks are ovoviviparous, meaning that eggs are hatched within the body of the parent. They engage in internal reproduction in which sperm from the male fertilizes the egg within the female. The breeding season is year-round. The number of offspring ranges from one to two, few for a shark. Females reach sexual maturity at 12.3 to 13.4 years and males reach sexual maturity at nine to 10 years. [Source: John Lewis, Animal Diversity Web (ADW) /=]

Thresher teeth

Common thresher sharks are polygynous (males having more than one female as a mate at one time) but little is known about their mating behavior. According to Animal Diversity Web: The migratory patterns of common thresher sharks near North America suggest they breed in northern waters during the spring and summer and release their pups into nurseries along the coast as they travel south for the winter months.

There is no parental involvement in the raising of offspring. Females can only carry two pups at a time. Pups are born independent, but remain in a nursery area for approximately three years for safety. Pups are easy targets for larger predators and usually stay in shallow water areas that are separate from adults as a defense from predation from adult thresher sharks and other sharks.. Threshe sharks grow fairly slowly and take some time to reach maturity.

Humans, Thresher Shark and Conservation

Humans utilize thresher sharks for food and leather. Their body parts are sources of valuable materials. They are fished fr sport in some places, including the U.S. Because common thresher sharks stay beyond areas where humans swim, they do not pose a threat to people engaging in sea-related activities. Fishermen don’t like them because they can damage or destroy nets and other equipment. [Source: John Lewis, Animal Diversity Web (ADW) /=]

Common thresher sharks are familiar figures in the global commercial fishing. Although they are not sought out by fishermne are often incidentally caught in commercial gill nets. In China and other countries they are the third most targeted catch of fisheries. Common thresher sharks meat and fins are sold in Chinese fish markets. In some places, the demand for thresher shark meat and fins has led to overfishing and decreases in their population sizes. The livers of common thresher sharks contain a small amount of oil, which is considered valuable among some buyers.

International Union for Conservation of Nature (IUCN) Red List lists thresher shark as Vulnerable; They have no special status according to the Convention on the International Trade in Endangered Species (CITES). In many areas of the Atlantic ocean, populations of common thresher sharks were reduced up to 67 percent in a ten years period. In the Pacific Ocean, where there are stricter catch-and-release policies, populations are more stable.

Pacific Common Thresher Shark

world record thresher shark caught off New Zealand

Pacific common thresher sharks are bluish gray with a white underbelly and sickle-shaped tail fin. They are sometimes seen around Pacific Islands and the west coast of the U.S. U.S. wild-caught Pacific common thresher shark is considered a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations. The shark boasts above target population level and its fishing rate is at recommended level. [Source: NOAA]

Drift gillnets and harpoons used to catch common thresher sharks have no impact on habitat because they’re used in the water column and don’t contact the ocean floor. Regulations are in place to minimize bycatch. According to the 2018 stock assessment, Pacific common thresher shark is not overfished and not subject to overfishing. In 2020, a total of 61,234 kilograms (135,000 pounds) of thresher shark, valued at more than US$92,000, was caught by commercial fishermen according to the NOAA Fisheries commercial fishing landings database. Most thresher sharks are landed in California.

Pacific common thresher shark grow slowly and a long time, between 19 and 50 years. They mature when they reach about 5 years old and 1.5 meters (5 feet) in length. They mate in midsummer. They are found in the Eastern Pacific Ocean from Goose Bay, British Columbia, south to Baja California. They’re also found off Panama and Chile. They migrate seasonally between Oregon and Washington and southern California and the Baja Peninsula of Mexico.

NOAA Fisheries and the Pacific Fishery Management Council manage the Pacific common thresher shark fishery on the West Coast. Permits are needed to fish for highly migratory species, including thresher sharks, and fishermen must maintain logbooks documenting their catch. There are annual commercial harvest guidelines that give a general objective on how many can be caught. Fishermen are required to take a training course on safe handling and release of protected species.

The Shark Conservation Act requires that all sharks, with one exception, be brought to shore with their fins naturally attached. Management of highly migratory species, like thresher sharks, is complicated because the species migrate thousands of miles across international boundaries and are fished by many nations. Two international organizations, the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC) manage highly migratory species, like sharks, internationally. No international measures are in place specific to common thresher sharks, but both organizations have passed shark conservation and management measures that combat shark finning practices and encourage further research and periodic stock assessment efforts for sharks.

Atlantic Common Thresher Shark

Atlantic common thresher shark range from Newfoundland to Cuba in the northwest Atlantic Ocean, They are seen in waters off in the U.S. off New England, the Mid-Atlantic and Southeast. According to NOAA, U.S. wild-caught Atlantic common thresher shark is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations. The stock has never been assessed. The population level is unknown, but presumed stable.[Source: NOAA]

Atlantic common thresher shark grow slowly, but can reach up to six meters (20 feet) long. Males sexually mature when they’re 2.5 to 3.5 meters (8 to 11 feet) long and three to six years old. Females are able to reproduce when they’re 2.5 to 2.7 meters (8 to 9 feet) long and 4 to 5 years of age. Atlantic Common thresher sharks feed on schooling fish such as herring and mackerel and occasionally on squid and seabirds.

NOAA Fisheries and the Atlantic Highly Migratory Species Division manage the Atlantic common thresher shark fishery in the United States. Permits are required, and only a limited number of permits are available. Gear used to harvest Atlantic common thresher shark does not contact the ocean floor and has no impact on habitat. Bycatch is low because Atlantic common thresher sharks are primarily incidental catch in other fisheries. Commercial quotas and limits on how many sharks can be landed per fishing trip. Shark dealers are required to attend Atlantic shark identification workshops to help them better identify shark species. Prohibited species — there are more than 20 species of sharks that cannot be landed (such as, white, dusky, basking, longfin mako, night). Some of these species look similar to the species that can be landed.

In 2020, commercial landings of Atlantic common thresher shark totaled 36,287 kilograms (80,000 pounds) and were valued at $45,000, according to the NOAA Fisheries commercial fishing landings database. Most of this catch comes from New Jersey and North Carolina.

Atlantic common thresher sharks are primarily caught incidentally in longline fisheries targeting swordfish and tuna. Highly migratory species, such as thresher sharks, have complicated management that requires international cooperation. A shark that is off the coast of Florida one week could be caught off the coast of Mexico the next. These resources must be managed both in the United States and at the international level.

Recreational fishermen fish for common thresher sharks, mainly with rod-and-reel gear. Recreational fishermen must have an Atlantic HMS permit to harvest Atlantic common thresher sharks in federal waters. As of 2018, all HMS recreational permit holders will need a “shark endorsement” to fish for, retain, possess, or land sharks. In 2020, recreational anglers landed 226,800 kilograms (500,000 pounds) of common thresher shark, according to the NOAA Fisheries recreational fishing landings database.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023

This site contains copyrighted material the use of which has not always been authorized by the copyright owner. Such material is made available in an effort to advance understanding of country or topic discussed in the article. This constitutes 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. If you are the copyright owner and would like this content removed from, please contact me.