Atlantic Common Thresher Shark (Alopias vulpinus)

• Atlantic thresher shark populations are estimated to be high, but it is unknown whether overfishing is occurring.
• Since common thresher sharks are highly migratory, they are managed by a number of national and international agencies, including NOAA's Highly Migratory Species Division.
• Shark is high in protein and low in fat. It is a good source of niacin, vitamins B6 and B12, and phosphorus and a very good source of selenium. Shark may contain amounts of methylmercury in excess of the FDA's recommended limit for moms, moms-to-be, and young children. For more information, see EPA and FDA advice on what you need to know about mercury in fish and shellfish.
• About 90% of the thresher shark landed in the U.S. in 2006 were Pacific thresher shark; only about 10% were from the Atlantic fishery.

Sustainability Status

Biomass: Unknown
Overfishing: Unknown
Overfished: Unknown
Fishing and habitat: In the Atlantic, thresher sharks are targeted by pelagic longlines. Longline gear has few impacts on open water habitats.
Bycatch: Finfish, along with sea turtles, marine mammals, and seabirds were identified as bycatch concerns for the pelagic longline fishery in the 2003 Highly Migratory Species Bycatch Reduction Plan. Pelagic longline gear sometimes catches non-target finfish with little or no commercial value, as well as species that cannot be retained by commercial fishermen due to regulations, such as billfish. Pelagic longlines may also interact with protected species such as marine mammals, sea turtles, and seabirds. Area closures are used to decrease bycatch by closing the areas with the highest rates of bycatch. Vessel Monitoring Systems are required on pelagic longline vessels to enforce closures and monitor the fishery. Circle hooks are also required to increase post-release survival of animals that are inadvertently caught. Additionally, pelagic longline fishermen must attend workshops to learn how to properly handle and release these animals. The Atlantic Ocean, Caribbean, and Gulf of Mexico large pelagics longline fishery is a Category I fishery according to the Marine Mammal Protection Act's annual List of Fisheries. This means that annual mortality and serious injury of certain marine mammal stocks in this fishery is greater than or equal to 50 percent of the Potential Biological Removal level. NMFS is addressing this challenge through the Pelagic Longline Take Reduction Team.
Aquaculture: There is currently no commercial aquaculture of thresher shark in the United States.

Science and Management

In the Atlantic and Gulf of Mexico, common thresher shark is managed by NOAA's National Marine Fisheries Service (NMFS) Highly Migratory Species Management Division through the 2006 Consolidated Atlantic Highly Migratory Species (HMS) Fishery Management Plan (FMP). This FMP combined the 1999 FMP for Atlantic Tunas, Swordfish, and Sharks (and its 2003 amendment) and the Atlantic Billfish FMP. The 1999 FMP included numerous measures to rebuild or prevent overfishing of Atlantic sharks in commercial and recreational fisheries, such as quotas, recreational minimum sizes and retention limits, and limited access in commercial fisheries.

Because highly migratory species move throughout large areas of the Atlantic Ocean and are fished by many nations and gear types, management by the United States alone is not enough to ensure that harvests are sustainable in the long term. The United States plays an important part in negotiating with Regional Fisheries Management Organizations, including the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Food and Agriculture Organization of the United Nations (FAO), and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), to increase shark management worldwide.

Scientists at the NMFS Northeast Fisheries Science Center are conducting age and growth studies on thresher shark in cooperation with scientists at the University of Rhode Island. Life history studies are also being continued; data collection has been augmented to include reproductive and food habits, in addition to age and growth information.

Life History and Habitat

Life history, including information on the habitat, growth, feeding, and reproduction of a species, is important because it affects how a fishery is managed.

• Geographic range: Thresher sharks are distributed around the world in the Atlantic, Pacific, and Indian Oceans and in the Mediterranean.
• Habitat: Thresher sharks live in temperate and warm oceans but also penetrate into tropical waters. They are most abundant over continental and insular shelves and slopes. This species is often found in areas of high productivity where schooling pelagic prey are abundant.
• Life span: Estimates of maximum age vary from 19 to 50 years.
• Food: Fish and squid
• Growth rate: Slow
• Maximum size: 20 feet
• Reaches reproductive maturity: Females mature between 8 and 9 feet long, at about 4 or 5 years old. Males mature between 8 and 11 feet long, between 3 and 6 years old.
• Reproduction: Relative to other marine fish, sharks have a very low reproductive potential. Thresher sharks bear live young. A normal brood size appears to be 2 to 4 fetuses. The developing fetuses feed on yolk-filled egg capsules produced by the female and consumed in utero. The gestation period lasts about 9 months.
• Spawning season: Midsummer
• Spawning grounds: Unknown
• Migrations: Thresher sharks are highly migratory species. They are pelagic, ranging widely in the upper zones of the oceans and often traveling over entire ocean basins.
• Predators: Thresher sharks have no known predators.
• Commercial or recreational interest: Both
• Distinguishing characteristics: The thresher shark is brown, gray, blue-gray, or blackish on its back and underside of its snout, lighter on the sides, and abruptly white below. A white area extends from the abdomen over the pectoral fin bases. The pectoral, pelvic, and dorsal fins are blackish, and white dots are sometimes present on pectoral, pelvic, and caudal fin tips. The caudal fin is sickle-shaped, and the upper lobe is extremely long - about 50% of total body length.

Role in the Ecosystem

As top predators in the sea, sharks provide a valuable balance to the marine ecosystem. Humans are one of the few species that prey on sharks, killing over 100 million per year (killer whales and other sharks are also predators).

Additional Information

Market name: Thresher Shark
Vernacular name: Fox Shark, Sea Fox, Swingletail, Whiptail Shark, Thintail Shark
Bigeye and pelagic thresher sharks are also marketed as Thresher Shark.

Biomass

Biomass refers to the amount of thresher shark in the ocean. Scientists cannot collect and weigh every single shark to determine biomass, so they use models to estimate it instead. These biomass estimates can help determine if a stock is being fished too heavily or if it may be able to tolerate more fishing pressure. Managers can then make appropriate changes in the regulations of the fishery. Biomass estimates for thresher sharks are unknown at this time.

Landings

Landings refer to the amount of catch that is brought to land. In the Atlantic and Gulf of Mexico, commercial landings of thresher sharks) ranged from a high of 96,266 pounds in 1999 to a low of 44,915 pounds in 2004.

Note: Only domestic commercial landings are shown in the graph.

Biomass and Landings

Are landings and biomass related? Landings are dependent on biomass, management measures in the fishery, and fishing effort.

Data sources:
Landings from the 2006 Consolidated Atlantic Highly Migratory Species Fishery Management Plan

Important Dates

Late 1970s-1980s – Growing demand for shark products encourages expansion of the commercial fishery; the movie "Jaws" encourages recreational anglers to fish for sharks
1980s – As catches accelerate, shark stocks suffer a precipitous decline
1989 – Peak commercial landings of large coastal and pelagic (includes thresher) sharks reported in Atlantic and Gulf
1993 – NMFS implements FMP for Sharks of the Atlantic Ocean; establishes commercial and recreational harvest limits for all sharks
2003 – Amendment 1 to the Atlantic Shark FMP eliminates commercial minimum size restrictions, implements commercial fishing seasons, imposes gear restrictions to reduce bycatch, and implements a time/area closure off the coast of North Carolina
2004 – ICCAT adopts a recommendation concerning the conservation of sharks caught in association with fisheries managed by ICCAT; includes reporting of shark catch data, a ban on shark finning, a request to live-release sharks that are caught incidentally, a review of management for shortfin, and a commitment to conduct another stock assessment of selected pelagic shark species no later than 2007

Notes and Links

General Information:
NMFS Shark Web Site

NMFS Office of Sustainable Fisheries Highly Migratory Species Division - Sharks

Fishery Management:
2006 Consolidated Atlantic Highly Migratory Species (HMS) Fishery Management Plan (FMP)

Stock Assessments:
NMFS Highly Migratory Species Stock Assessment and Fishery Evaluation Reports