Common thresher sharks, like many shark species, are especially vulnerable to overfishing because they live a long time, 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 – 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.
- Ocean perch
- Sea Bass
- Turbot (Greenland)
Pacific Common Thresher Shark
ALSO KNOWN AS:
Thresher Shark, Fox Shark, Sea Fox, Swingletail, Whiptail Shark, Thintail Shark
U.S. wild-caught from California
- FISHING RATE
- HABITAT IMPACTS
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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. Most of the catch comes from the pelagic drift gillnet fishery that mainly targets swordfish. 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 over 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. Catch also declined due to new management measures to protect the thresher shark resource and protected species incidentally caught in the fishery. A small amount is also incidentally harvested in U.S. fisheries targeting other fish in both the Pacific and Atlantic.
The West Coast drift gillnet fishery operates under a suite of state and federal management measures that ensure the common thresher shark resource is protected and the seafood provided by this fishery is harvested responsibly. 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. Common thresher sharks are also harvested by several nations in temperate waters around the world.
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 common close to shore and are often found in areas rich with plankton, where their prey is also abundant.
Thresher sharks are highly migratory species, travelling seasonally as temperatures change. In the eastern Pacific Ocean, they migrate between Oregon/Washington and southern California/Baja Peninsula, Mexico.
Common thresher sharks grow slowly, up to 18 feet, and live a long time, 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.
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.
Scientists have not assessed the Pacific common thresher shark stock recently. We share this resource with Mexico and are working with Mexican scientists to collect data on the stock. Scientists anticipate a new assessment will be available in 2013.
Scientists at NOAA’s Southwest Fisheries Science Center have developed an index of abundance for Pacific common thresher shark using catch data. Based on the best available science, Pacific common thresher shark is not overexploited.
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.
Scientists recently released results of a study analyzing the stomach contents of shortfin mako, blue, and common thresher sharks in the California Current. The new information should help researchers characterize differences among the species as well as their roles in the ecosystem.
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, mainly ocean sunfish and blue shark. Management limits both where and when drift gillnetters can fish to reduce bycatch. Historically, there have been concerns about bycatch of marine mammals and turtles in this fishery; however, after changes in fishing practices to minimize interactions with protected species, managers believe there is now only a remote likelihood of incidental mortality or serious injury to marine mammals and sea turtles. Scientists and managers continue to monitor bycatch through logbooks and vessel observer programs.
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.
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 and the Western and Central Pacific Fisheries Commission . 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.
Current management: A federal law prohibits the practice of "shark finning," where valuable shark fins are removed and the remainder of the shark is discarded at sea.
- Commercial fishermen must have a permit to fish for highly migratory species 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.
- An annual commercial harvest guideline for thresher sharks (a harvest guideline is a general objective for how much should be caught every 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 and fishing effort.
No specific management measures apply to this species, 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.
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.
Fresh thresher shark catch is mainly sold to domestic restaurants, seafood markets, and grocery stores.
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.
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.
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.
|Serving Weight||100 g (raw)|
|Fat, total||4.51 g|
|Saturated fatty acids, total||0.925 g|
|Sugars, total||0 g|
|Fiber, total dietary||0 g|
Pacific Common Thresher Shark Table of Nutrition