Atlantic Common Thresher Shark (Alopias vulpinus)

• Atlantic common thresher shark population levels are unknown, and 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 Management 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.
• Over 85% of the common thresher shark landed in the U.S. in 2007 were from the Pacific Ocean; only about 15% were from the Atlantic fishery.

Sustainability Status

Biomass: Unknown
Overfishing: Unknown
Overfished: Unknown
Fishing and habitat: In the Atlantic, common thresher sharks are mainly captured by pelagic longlines. In U.S. fisheries, they are generally caught commercially as bycatch by pelagic longliners that are targeting swordfish and tuna, and recreationally by rod and reel. Pelagic longline gear has no impact on ocean floor habitats, because it does not come in contact with the bottom.
Bycatch: 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 minimize bycatch by closing ocean areas that historically have the highest rates of bycatch, and Vessel Monitoring Systems are required on U.S. Atlantic 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, U.S. Atlantic pelagic longline fishermen must attend workshops to learn how to properly handle and release these animals. The Atlantic, Caribbean, and Gulf of Mexico pelagic longline fishery is designated as a Category I fishery according to the List of Fisheries published annually by NMFS as required under the Marine Mammal Protection Act. This means that annual mortality and serious injury of certain marine mammal stocks in this fishery are greater than or equal to 50% of the Potential Biological Removal level (the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing it to be at sustainable levels). NMFS is addressing this challenge through the Pelagic Longline Take Reduction Team, which works to reduce serious injuries and mortalities of short-finned pilot whales, long-finned pilot whales, and Risso's dolphins in the Mid-Atlantic portion of the Atlantic pelagic longline fishery. Rod and reel is considered a Category III fishery, and has minimal impacts on protected species.
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. Amendment 2 to the Consolidated HMS FMP became effective in July 2008, and is the most recent update to the regulations contained in the Consolidated HMS FMP. Regulations include numerous measures to rebuild or prevent overfishing of Atlantic sharks in commercial and recreational fisheries. Some measures utilized to protect common thresher shark in U.S. Atlantic fisheries are commercial quotas and trip limits, recreational minimum sizes and retention limits, and limited access in commercial fisheries.

Because the common thresher shark is a highly migratory species that travels across large areas of the Atlantic Ocean, they are fished by many different nations with a variety of gear types. Therefore, management by the U.S. alone is not enough to ensure that harvests are sustainable in the long term. The U.S. plays an important part in negotiating with Regional Fisheries Management Organizations to enhance shark management worldwide, 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).

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 conducted. 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: Common thresher sharks are distributed around the world in the Atlantic, Pacific, and Indian Oceans and in the Mediterranean. In the northwest Atlantic Ocean, thresher sharks range from Newfoundland, Canada to Cuba.
• Habitat: Common thresher sharks are most common in temperate waters but can also be found in cold-temperate and tropical seas. 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: Mainly schooling fish such as herring and mackerel. Common thresher sharks are also known to eat squid and seabirds.
• 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. Common 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: Common 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: Common thresher sharks have few 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, common thresher sharks provide a valuable balance to the marine ecosystem and have few predators. Younger, smaller common thresher sharks may fall pretty to larger sharks from a variety of species. Humans are one of the few species that prey on sharks.

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 common thresher shark in the ocean. Scientists cannot collect and weigh every single shark to determine biomass, so they use mathematical 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 U.S. Atlantic common 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, recent commercial landings of thresher sharks ranged from a high of 56,893 pounds in 2001 to a low of 24,280 pounds in 2005.

Note: Only domestic commercial landings from the Atlantic Ocean and Gulf of Mexico are shown in the graph.

Biomass and Landings

Landings and biomass data can sometimes be used to detect trends in a fishery. Because there is no biomass data for common thresher shark, it is difficult to determine if the decrease in landings since 1999 is a result of decreasing biomass, increasing fishing effort, or a combination of both. Other factors, such as changes in management measures, market preferences, or environmental conditions may have contributed to the decline in landings as well. The common thresher is a highly migratory species that moves outside of U.S. waters, therefore fishing practices of foreign countries could affect U.S. Atlantic common thresher landings and the biomass of the population. Also, recreational fishing efforts may impact common thresher shark populations.

Data sources:
Landings from the 2007 Stock Assessment and Fishery Evaluation Report for Atlantic Highly Migratory Species

Important Dates

1966 – International Convention for the Conservation of Atlantic Tunas is signed creating the International Commission for the Conservation of Atlantic Tunas (ICCAT)
Late 1970s-1980s – Growing demand for shark products encourages expansion of the commercial fishery
1980s – As catches accelerate, shark stocks suffer a precipitous decline
1989 – Peak commercial landings of large coastal and pelagic (includes common thresher) sharks reported in Atlantic and Gulf
1990 – Magnuson Act amended, giving authority to Secretary of Commerce to manage Atlantic tunas; secretarial authority is delegated to NMFS
1992 – NMFS creates the HMS Management Division to manage Atlantic tunas, sharks, swordfish, and billfish.
1993 – NMFS implements FMP for Sharks of the Atlantic Ocean; establishes commercial and recreational harvest limits for all sharks
1997 – NMFS reduces recreational retention limit for large coastal and pelagic sharks, including common thresher sharks, from 4 to 2 sharks per vessel per trip
1999 – NMFS implements the FMP for Atlantic Tunas, Swordfish, and 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
2006 – Consolidated Atlantic Highly Migratory Species Fishery Management Plan is approved, which requires sharks to be landed with their second dorsal fin attached and creates new time/area closures.
2008 – NMFS implements Amendment 2 to the Consolidated Highly Migratory Species Fishery Management Plan to address overfishing of some shark species by instituting new commercial fishing trip limits (33 large coastal sharks per trip) and prohibiting the harvest of sandbar shark (Carcharhinus plumbeus) unless fishing within the newly established Shark Research Fishery

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)

Amendment 2 to the Atlantic HMS Fishery Management Plan

Stock Assessments:
2007 Stock Assessment and Fishery Evaluation Report for Atlantic Highly Migratory Species