Yellowfin Tuna: Fishing, Records and a Missing Fisherman | Sea Life, Islands and Oceania

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YELLOWFIN TUNA

Yellowfin tuna is one of the main components of canned tuna and one of the most heavily fished of all fishes. Often marketed as ahi, it is popular in sushi and s widely consumed in Japan in sashimi and sushi. In the late 2000s, around 20,000 to 38,000 tons of the annual catch of 100,000 to 150,000 tons of the fish caught in central and western Pacific is consumed in Japan. Yellowfin tuna are found in huge schools near the surface that are scooped up with purse seine nets and caught with hooks and lines. Because overfishing of the fish is regarded as a serious problem in some places fishing experts have called for a 30 percent reduction of the yellowfin tuna catch,

Also known as kihada, Yellowfin tuna (Scientific name: Thunnus albacares) are torpedo-shaped. They are metallic dark blue on the back and upper sides and change from yellow to silver and white on the belly. True to their name, their dorsal and anal fins and finlets are bright yellow. An adult yellowfin tuna can be distinguished from other tunas by its long, bright-yellow dorsal fin and a yellow stripe down its side. [Source: NOAA]

Yellowfin tuna grow fast, up to two meters (6 feet) long and 181 kilograms (400 pounds) and have a somewhat short life span of 6 to 7 years. Most yellowfin tuna are able to reproduce when they reach age two. Adult yellowfin tuna feed near the top of the food chain on fish, squid, and crustaceans. Fish, seabirds, dolphins, and other animals prey on larval and juvenile tuna. Marine mammals, billfish, and sharks feed on adult tuna..

Yellowfin tuna are found in tropical and subtropical oceans around the world, including the waters around the U.S. Pacific Islands and off southern California. They favor water temperatures between 18̊ and 31̊C (64° and 88° F). Yellowfin tuna are highly migratory and travel long distances throughout the warm ocean. They make annual trips to higher latitudes as water temperatures increase with the seasons. Yellowfin tuna are known to gather around drifting flotsam (natural floating debris), fish aggregating devices (FADs), anchored buoys, dolphins, and other large marine animals. Adult yellowfin also gather in areas having abundant phytoplankton and zooplankton and smaller prey..

Yellowfin tuna spawn throughout the year in tropical waters and seasonally at higher latitudes. Their peak spawning periods are in spring and fall. Yellowfin are very productive. Females can spawn almost daily and release millions of eggs each time they spawn. Larval and juvenile yellowfin tuna stay in surface waters, while older yellowfin tuna are often found in deeper water.

Websites and Resources: “Netting Billions 2020: A Global Tuna Valuation, Pew Charitable Trusts”, October 6, 2020 pewtrusts.org; Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Yellowfin Tuna Fishing in the U.S.

1,352,204 tonnes (1000 kilograms) of yellowfin tuna was caught globally, the six most among wild-caught fish according to the Food and Agriculture Organization of the United Nations (FAO). U.S. harvest of yellowfin tuna in the Pacific Ocean makes up only a small percentage of the yellowfin tuna harvested worldwide. In 2020, the commercial landings in the U.S. of Pacific yellowfin tuna totaled 3.6 million kilograms 8 million pounds and were valued at more than $16 million, according to the NOAA Fisheries commercial fishing landings database. In 2020, recreational anglers landed approximately 4.5 million pounds of Pacific yellowfin tuna, according to the NOAA Fisheries recreational fishing landings database. [Source: NOAA]

Yellowfin

Fishermen based in Hawaii, American Samoa, and the U.S. Pacific Islands target Pacific yellowfin tuna with hook-and-line, pelagic longline, or troll fishing gear. U.S. commercial purse seine fishermen in the western and central Pacific Ocean and the eastern Pacific Ocean also harvest yellowfin tuna. There is a small U.S. purse seine fleet operating in the eastern Pacific Ocean that sometimes targets Pacific yellowfin tuna when warm water from the south brings the species within their range.

Fishing gear used to catch Pacific yellowfin tuna rarely contacts the seafloor so habitat impacts are minimal. Restrictions on the type of fishing gear that can be used and prohibitions on fishing in certain areas minimize impacts on protected species. Interactions with protected species such as sea turtles, marine mammals, and seabirds in these fisheries are rare and survival rates are estimated to be high for all gear types. Longline fishermen are trained in safe handling and release techniques for sea turtles, seabirds, and marine mammals, and they carry and use specific equipment for handling and releasing these animals. Scientists and managers continue to monitor bycatch in these fisheries through logbooks and fishery observer programs. Management measures are in place to minimize bycatch of juvenile Pacific yellowfin tuna.

U.S. wild-caught Pacific yellowfin tuna is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations. There are above target population levels. The fishing rate is at recommended levels in the western and central Pacific Ocean and in the eastern Pacific Ocean. Fishing gear used to catch Pacific yellowfin tuna rarely contacts the seafloor so habitat impacts are minimal. Regulations are in place to minimize bycatch. Population Status: There are two stocks of Pacific yellowfin tuna: The Eastern Pacific stock and the Central and Western Pacific stock. According to the most recent stock assessments: Both are not overfished and not subject to overfishing (2020 stock assessment).

Yellowfin Tuna Fishing Management in U.S. Waters

NOAA Fisheries and the Pacific Fishery Management Council manage the Pacific yellowfin tuna fishery on the West Coast. The species are managed under the Fishery Management Plan for U.S. West Coast Fisheries for Highly Migratory Speciess. Fishermen are required to have permits and to record their catch in logbooks. Gear restrictions and operational requirements are in place to minimize bycatch. Large purse seine vessels that fish for tuna in the eastern Pacific Ocean are required to have 100 percent observer coverage. All other commercial vessels based on the U.S. West Coast must carry a fishery observer, if requested by NOAA Fisheries. Longline fishing is prohibited within 200 miles of the U.S. West Coast. Annual training in safe handling and release techniques for protected species is required and all vessels must carry and use specific equipment for handling and releasing these animals.

yellowfin tuna
NOAA Fisheries and Western Pacific Fishery Management Council manage the Pacific yellowfin tuna fishery in the Pacific Islands. The species are managed under the Fishery Ecosystem Plan for the Pelagic Fisheries of the Western Pacific. Fishermen are required to have permits and to record catch in logbooks. Gear restrictions and monitoring requirements are in place to minimize bycatch and potential gear conflicts between different fisheries. A limit on the number of permits for Hawaii and American Samoa longline fisheries controls participation in the fishery.

Longline fishing is prohibited in some areas to protect endangered Hawaiian monk seals, reduce conflicts between fishermen, and prevent localized stock depletion (when a large number of fish are removed from an area). These areas are enforced through NOAA Fisheries’ vessel monitoring system program (longline boats must be equipped with a satellite transponder that provides real-time position updates and tracks vessel movements). Hawaii-based and American Samoa–based longline vessels must carry onboard observers when requested by NOAA Fisheries, in part to record interactions with sea turtles, seabirds, and marine mammals. Annual training in safe handling and release techniques for protected species is required and all vessels must carry and use specific equipment for handling and releasing these animals.

Management of highly migratory species, like Pacific yellowfin tuna, is complicated because the species migrate thousands of miles across international boundaries and are fished by many nations. Effective conservation and management of this resource requires international cooperation as well as strong domestic management. Two international organizations, the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC), manage this fishery internationally. Working with the U.S. Department of State, NOAA Fisheries domestically implements the IATTC and WCPFC conservation and management measures.

Under the South Pacific Tuna Treaty, U.S. purse seine vessels operating throughout the western and central Pacific Ocean must be registered and are monitored through logbooks, cannery landing receipts, national surveillance activities, observers, and port sampling. Purse seiners in the eastern Pacific Ocean also operate under the International Dolphin Conservation Program, a multilateral agreement aimed at reducing and minimizing bycatch of dolphins and undersize tuna. In 2000, the United States established the Dolphin-Safe Tuna Tracking and Verification Program to monitor the domestic production and importation of all frozen and processed tuna products nationwide and to authenticate any associated dolphin-safe claim.

Man Catches 195-Kilogram Monster Yellowfin Tuna Off Mexico

Recreational anglers fish for yellowfin tuna with troll, rod-and-reel, and handline gear and sometimes by free-diving with spear guns. Off California, anglers must be licensed and daily bag limits are in place. Recreational charter boats must keep logbooks of their catch. There are no federal regulations for recreational fishing off Hawaii and U.S. Pacific Island territories, but local rules may apply.

In May 2016. Robert Ross caught a world record 195-kilogram (430-pound) yellowfin tuna off Loreto. Mexico but record didn’t count because the fish was weighed on an unofficial scale before it was cut up. Pete Thomas wrote in Grind TV: Ross knew the yellowfin tuna he landed was massive. What he did not know was that the 430-pound fish, weighed on a butcher’s scale at a nearby cattle ranch, was three pounds heavier than the world record. “Rather than seek a certified scale, Ross filleted the tuna and then telephoned Pisces Sportfishing to let general manager Tracy Ehrenberg know about his catch. ““Once they told me the weight of the fish, I told them, “You just cut up your world record,” Ehrenberg told GrindTV. [Source: Pete Thomas, Grind TV, May 11, 2016]

The 430-pound tuna was caught at a remote location with no certified scale. The International Game Fish Association world record stands at 427 pounds. That fish was also caught off Cabo San Lucas, in 2012. Only a handful of yellowfin weighing 400 pounds have ever been caught on rod-and-reel. Ross had launched his Boston Whaler last week from the remote Pisces Collection Lodge, on the Sea of Cortez. The lodge is still under construction and does not yet have a certified scale, or a cold storage facility. Ross told Ehrenberg that he had little choice but to process the meat, after weighing the fish at the cattle ranch; otherwise it might have spoiled. Ehrenberg quoted the angler as saying, “I kind of thought that it might be a record. It’s the biggest tuna I’ve caught, but what were we going to do with it? It’s important but not most important for me to get a record. Next time I’ll call you before cutting it up.” According to the Pisces Sportfishing Facebook page, the tuna was hooked on a chunk bait and landed after a 2-hour fight, standup-style, on a 60-pound test line. Loreto is in the state of Baja California Sur, on the Sea of Cortez, about 315 miles north of Cabo San Lucas.

Fisherman Missing Off Hawaii After Being Pulled Overboard by a Yellowfin Tuna

In January 2023, rescuer searched for three days for Mark Knittle, a 63-year-old Hawaiin fisherman who went overboard from a boat after hooking a yellowfin tuna. Knittle, of Captain Cook, was fishing with a friend off Honaunau on the Big Island on a Sunday when he hooked the fish. “The friend heard Knittle say, ‘The fish is huge,’ then saw Knittle go overboard into the water,” according to a police news release.

Associated Press reported: The friend tried to grab the line, but Knittle disappeared within seconds, the release said. The friend jumped in but couldn't see Knittle. “Usually our incidents like this are along the coastlines. This is a different situation because it's out in the deep," said Darwin Okinaka, Hawaii County Fire Department assistant chief of operations. [Source: Jennifer Sinco Kelleher, Associated Press, January 18, 2023]

According to police, Knittle and his friend were 4 miles (6.4 kilometers) from the Honaunau Boat Ramp. “If there's a fish that's actually pulling him around, you don't know where he could go," Okinaka said. Ahi can weigh several hundred pounds. Police described Knittle as weighing 185 pounds (84 kilograms).

Mercury Levels Rising in Hawaiian Yellowtail Tuna

Research published in 2015, revealed that mercury levels were rising in Hawaiian yellowfin tuna, often marketed as ahi, at a rate of nearly four percent a year as the oceans absorb the pollutant from the. AFP reported: Coal-fired power plants and artisanal gold mining operations produce mercury, a potent toxin that makes its way into the world's water and poses a health risk to people who eat certain fish. "Mercury levels are increasing globally in ocean water, and our study is the first to show a consequent increase in mercury in an open-water fish," University of Michigan researcher Paul Drevnick said. [Source: AFP, February 3, 2015]

Scientists have long expected to see rising mercury in fish, as a consequence of increasing air pollution due to industrialization, but evidence has been hard to find. For this study, published in the Environmental Toxicology and Chemistry journal, Drevick and colleagues took a second look at data from three studies that sampled the same yellowfin tuna population near Hawaii in 1971, 1998 and 2008. The studies tallied mercury levels in the muscle of captured yellowfin tuna.

The team's re-analysis included yellowfins between 48 and 167 pounds (22-76 kilograms) and used a computer model that controls for the effect of fish body size. In all, 229 fish were analyzed: including 111 from 1971 and 104 from 1998. In those years, no significant rise in mercury could be seen. However, when researchers compared 1998's sample to 14 yellowfin tuna — a far smaller size sample — from 2008, they found mercury had risen at a rate of about 3.8 percent per year.

Yellowfin tuna is already considered a "high mercury" species by the Natural Resources Defense Council. Drevnick said the study suggests that at the current rate, North Pacific waters will double in mercury by 2050. "The take-home message is that mercury in tuna appears to be increasing in lockstep with data and model predictions for mercury concentrations in water in the North Pacific," said Drevnick, an assistant research scientist at the University of Michigan School of Natural Resources and Environment. This study confirms that mercury levels in open ocean fish are responsive to mercury emissions."

Image Source: Wikimedia Commons, NOAA, graphics from The Pew Charitable Trusts (“Netting Billions 2020: A Global Tuna Valuation, October 6, 2020 pewtrusts.org)

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023