Pacific Common Thresher Shark

Pacific common thresher shark

Alopias vulpinus

ALSO KNOWN AS:

    Thresher Shark, Fox Shark, Sea Fox, Swingletail, Whiptail Shark, Thintail Shark

SOURCE:

    U.S. wild-caught from California
 

STATUS

  • POPULATION
  • FISHING RATE
  • HABITAT IMPACTS
  • BYCATCH
 

Click the icons to learn more about each criteria

 
 

OVERVIEW

Common Thresher Shark

Common thresher shark.

LAUNCH GALLERY

Not to be confused with pelagic and bigeye thresher sharks, common thresher sharks are one of the most commonly harvested sharks off the U.S. West Coast. Initially developed in the late 1970s, the West Coast drift gillnet fishery rapidly expanded as market demand grew, and harvests of thresher shark peaked in 1985 at more than 1,000 metric tons. As the market and prices for swordfish increased, catch of thresher shark declined and swordfish replaced it as the primary target species of the drift gillnet fishery. Today, most Pacific common thresher sharks are caught incidentally by fishermen targeting swordfish. They are also harvested by several nations in temperate waters around the world. Common thresher sharks are also found in the Atlantic; however there is no directed U.S. fishery for them on the East Coast (see Atlantic common thresher shark).

Catch of Pacific thresher sharks has also declined due to new management measures designed to ensure sustainability of the shark fishery and reduce the likelihood of incidentally catching protected species. Sharks harvested off the U.S. West Coast are primarily caught for their meat rather than their fins. Also, a key federal law prohibits the practice of “shark finning,” where valuable shark fins are removed and the remainder of the shark is discarded at sea. The United States is a leader in shark conservation, and NOAA Fisheries works to sustainably manage shark populations by conducting research, assessing stocks, working with U.S. fishermen, and implementing regulations.

Looking Ahead

Common thresher sharks, like many shark species, are especially vulnerable to overfishing because they take many years to mature and only have a few young at a time. Recovery from overharvest can take years or decades. Sharks require special attention by fishery managers. NOAA Fisheries is conducting research, implementing restrictions and working with fishermen domestically, and pursuing conservation of shark species worldwide to ensure that healthy shark populations stay healthy and that overfished populations recover.

 
 
 

LOCATION & HABITAT

Common thresher sharks are found in temperate and warm oceans around the world. In the eastern Pacific Ocean, they’re found from Goose Bay, British Columbia south to Baja California and also off Panama and Chile. They’re most commonly found close to shore in areas rich with plankton, where their prey is also abundant.

Thresher sharks are highly migratory, travelling seasonally as temperatures change. In the eastern Pacific Ocean, they migrate between Oregon/Washington and southern California/Baja Peninsula, Mexico.

 
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BIOLOGY

Common thresher sharks grow slowly, reaching a maximum of up to 18 feet. They live a long time, with a life expectancy between 19 and 50 years. Both males and females are able to reproduce when they reach about age 5 and around 5 feet in length. Compared to other marine fish, sharks aren’t very productive. Thresher sharks mate in the midsummer. Eggs are fertilized internally and develop inside the mother. After a gestation period of about 9 months, females bear live young in the spring. They typically have 2 to 4 pups.

Common thresher sharks are named for their long, scythe-like tail, which is used to swat and stun fish before preying on them. They feed at the mid-levels of the food chain, mainly on small pelagic fish, including anchovy, sardine, hake, and mackerel, as well as squid. They have small mouths and are no threat to humans. Top-level predators such as killer whales and larger sharks prey on common threshers.

 
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PHYSICAL DESCRIPTION

Common thresher sharks are brown, gray, blue-gray, or blackish on the back and underside of their snout. They’re lighter on the sides, and fully white below. Their pectoral, pelvic, and dorsal fins are blackish, and some have white dots on the tips of the pectoral, pelvic, and tail fins. The tail fin is sickle-shaped, and the upper part is extremely long, about half the length of their body.

 
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OVERVIEW

Scientists have not assessed the Pacific common thresher shark stock. We share this resource with Mexico and are working with Mexican scientists to collect data on the stock.

 
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POPULATION STATUS

The Pacific common thresher shark stock has never been assessed; the population status is unknown. However, scientists at NOAA’s Southwest Fisheries Science Center have developed an index of abundance for Pacific common thresher shark using catch data.

 
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ADDITIONAL RESEARCH

Researchers at NOAA’s Southwest Fisheries Science Center and Pacific Islands Fisheries Science Center study Pacific sharks to learn more about their biology, distribution, movements, stock structure, and status, as well as their potential vulnerability to fishing pressure. They share this information with international, national, and regional fisheries conservation and management bodies charged with the conservation and sustainable management of pelagic sharks and other highly migratory species.

A study analyzing the stomach contents of shortfin mako, blue, and common thresher sharks in the California Current provided new information that should help researchers characterize differences among the species as well as their roles in the ecosystem.

 
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Harvesting Common Thresher Sharks

Most of the total U.S. harvest of common thresher shark is from the West Coast drift gillnet fishery. A gillnet is a panel of netting suspended vertically in the water by floats, with weights along the bottom. Fish become entangled in the net. Drift gillnet gear is anchored to a vessel and drifts along with the current.

Drift gillnets can incidentally catch other species, such as ocean sunfish and blue sharks. Protected species such as sperm whales and leatherback sea turtles may also be caught as bycatch in the drift gillnet fishery. To limit bycatch, fishery managers limits both where and when drift gillnetters can fish. Scientists and managers continue to monitor bycatch through logbooks and onboard observer programs. NOAA Fisheries classifies U.S. commercial fisheries into one of three categories according to the level of incidental mortality or serious injury of marine mammals. The California thresher shark gillnet fishery is a Category I fishery meaning it has frequent incidental mortality and serious injury of marine mammals. NOAA Fisheries works with the federally-appointed Pacific Offshore Cetacean Take Reduction Team to develop measures that reduce the impacts of this fishery on certain marine mammals.

Small numbers of common thresher sharks are also landed by harpoon gear, in set net fisheries targeting halibut and angel sharks, and in the small mesh drift gillnet fishery for seabass. In the western and central Pacific Ocean, common thresher sharks are occasionally caught in Hawaii-based pelagic longline fisheries for swordfish. However, this species is not encountered as frequently as the other two thresher species.

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Management

Who’s in charge? NOAA Fisheries and the Pacific and Western Pacific Fishery Management Councils

Highly migratory species such as common thresher shark travel throughout large areas of the Pacific and are harvested by many nations. Effective conservation and management of this resource and fisheries that catch this species are not possible without international cooperation and strong domestic fishery management. There are no international management measures in place that are specific to common thresher sharks. The United States participates in bilateral meetings regarding shark management and research with Japan, Spain, Taiwan, the European Union, Canada, China, and Mexico. The United States is also an active member of the two international fisheries management organizations operating in the Pacific, the Inter-American Tropical Tuna Commission disclaimer and the Western and Central Pacific Fisheries Commission disclaimer. Both organizations have passed shark conservation and management measures that combat shark finning practices and encourage further research and periodic stock assessment efforts of sharks.

In the United States, federal law prohibits “shark finning,” a process of removing shark fins at sea and discarding the rest of the shark. This practice has been prohibited by federal law since 2000, but shark conservation was further strengthened in 2010 when Congress passed the Shark Conservation Act. The Shark Conservation Act requires that all sharks, with one exception, be brought to shore with their fins naturally attached.

Current management:

West Coast: Fishery Management Plan for U.S. West Coast Fisheries for Highly Migratory Species

  • Commercial fishermen must have a permit to fish for highly migratory species, including thresher sharks, and must maintain logbooks documenting their catch.
  • Two areas are closed seasonally to drift gillnetters to protect endangered leatherback and loggerhead turtles. Drift gillnetting is also prohibited within 3 miles of the coast where shark pups reside.
  • There is an annual commercial harvest guideline, a general objective for how much thresher shark should be caught each year.
  • Fishermen are required to take a training course on safe handling and release of protected species.
  • Mandatory placement (about 20 percent coverage) of at-sea observers on commercial drift gillnet vessels to monitor catch, bycatch, and fishing effort.
  • Fishing times and areas are tightly managed to reduce the risk of catching a protected species, such as sea turtles, whales, and dolphins.

Pacific Islands: Fishery Ecosystem Plan for Pacific Pelagic Fisheries of the Western Pacific Region

No specific management measures apply to this species in the Pacific Islands, as they’re only occasionally harvested incidentally in the longline fishery for swordfish. This fishery is regulated through area closures, gear restrictions, fishing permits, reporting and observer requirements, and limits on catch and fishing effort.

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Annual Harvest

Most U.S. catch of common thresher shark is from California (around 85 percent). Since 2004, total West Coast commercial shark landings have remained near or below 250 metric tons. The decline in landings reflects a decrease in drift gillnet effort, due in part to a large time/area closure implemented in 2001 to protect migrating and foraging leatherback sea turtles. In 2013, 66 metric tons of common thresher shark were landed on the West Coast.

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Economy

Fresh thresher shark catch is mainly sold to domestic restaurants, seafood markets, and grocery stores. The 2013 landings of Pacific common thresher shark were worth $117,626.

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Recreational

Recreational fishermen also fish for common thresher shark. Off the West Coast, recreational catch varies widely from year to year but has averaged roughly 20 metric tons annually in recent years. Catch is estimated from angler surveys and dockside sampling. Recreational fishermen are limited to two thresher sharks per day. To better understand the impact of recreational fishing on the thresher shark, NOAA is working with external partners and anglers to study fishing practices, determine how many thresher sharks live or die after release, and to find ways to decrease the number of thresher sharks caught by their tails.

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OVERVIEW

Common thresher shark has a mild flavor. It’s firm, dense, and meat-like in texture. Raw thresher shark is white to tan with a pink blood line.

 
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SEASONAL AVAILABILITY

Year-round

 
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NUTRITION

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 nursing 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. disclaimer

Servings 1
Serving Weight 100 g (raw)
Calories 130
Protein 20.98 g
Fat, total 4.51 g
Saturated fatty acids, total 0.925 g
Carbohydrate 0 g
Sugars, total 0 g
Fiber, total dietary 0 g
Cholesterol 51 mg
Selenium 36.5 mcg
Sodium 79 mcg

Pacific Common Thresher Shark Table of Nutrition

 
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