How tuna is caught
Yellowfin tuna can swim at up to 75 km/h, among the fastest fish in the open sea.
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The short version
Most commercial tuna are caught at sea with purse-seine nets, which have become the dominant gear. A boat encircles a school with a long net, then pulls the bottom closed like a drawstring purse. Longlines are the other major method, and older hook-and-line fishing once took most of the catch.
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Find the school
Tuna live in tropical and temperate seas and move widely. Fleets search for schools of the five principal market species, which include yellowfin, bigeye and bluefin tuna.
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Encircle it with a net
A purse seine is a net that hangs vertically in the water, with weights holding the bottom edge down and floats on top. A boat sets it around the school, and the net encloses the fish rather than snaring them as a gillnet would.
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Haul the catch aboard
The net is closed and drawn in, and the tuna are brought aboard the vessel. Longline boats set long lines of baited hooks as an alternative.
Worth repeating
- Tuna keep a core body temperature of 25 to 33 °C, warmer than the sea around them.
- The Atlantic bluefin can reach 4.6 m in length and 684 kg in weight.
- Annual world catches rose from about 300 thousand tons in 1940 to more than 4 million tons in the years before the report, as purse seines became the main gear.
Where it comes from
- Pacific Oceanabout 68% of the catch
- Indian Oceanabout 22% of the catch
Share of the global catch of the five principal market tunas, from a report based on 2007 catches.
Where it goes next
Tuna feeds 1 line directly.
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Sources
Cite this page: "How tuna is caught." Assembly Line, 2026-11-03. https://assemblyline.org/make/tuna-fish