FishWatch

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.

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 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.

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 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.

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

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.

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.

Economy

Fresh thresher shark catch is mainly sold to domestic restaurants, seafood markets, and grocery stores.

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.