Pacific Bluefin Tuna

Found as deep as 550 m (1800 ft) and can weigh up to 450 kg (990 lbs)!

Taxonomic description

• Body is streamlined and black or blue with grey-green iridescence; underside has spots of silver or grey, which appear as bands; second dorsal to tail fins are yellow with black edges. ^[1]
• Tip of the pectoral fin does not reach the front of the second dorsal fin and has a lunate tail. ^[1]
• Averages 1.5 m (4 ft 11 in), in length and weights around 60 kg (130 lbs), with record length of 3 m (9 ft 8 in), and weight of 450 kg (900 lbs)! ^[1]

Distribution

• Primarily found in sub-tropical and temperate Pacific Ocean between 20-50 degrees North; also in tropical waters off New Zealand in the Tasman Sea. ^[3]

Life history

• Spawns from mid-April to June, in the Sea of Japan and the southwestern North Pacific Ocean, during this time the females produce up to 10 million eggs a year. ^[1]
• When young, it migrates over 8,000 km (5,000 mi) from the Sea of Japan to the coast of California to feed and grow for several years. ^[9]
• Travels up and down the California coast between Washington and Mexico until about the age of 7 when it returns to the coast of Japan to spawn. ^[9]
• Matures at around 5 years and has a life expectancy of 26 years; average lifespan is 15 years. ^[1]

Habitat

• Pelagic; as one of the fastest fish in the ocean, it travels in large schools in open-water, coastal sea or near seamounts. ^[3,1]
• Starts off its larval stage by selectively eating tiny copepods, and eventually moves up the food chain to be a generalist predator who eats a variety of prey, including squid, anchovies, and even crustaceans! ^[4]
• Predators of this fish include, sharks, orcas, and pilot whales; it also faces human fishing pressure which is of particular concern when targeted in spawning areas. ^[1]
• Migration and spawning patterns are affected by increasing ocean temperatures, acidification, and nitrate levels; and decreased dissolved oxygen concentrations and trophic production associated with climate change. ^[4]

Commercial bluefin tuna fishing usually utilizes the purse seine method, which uses floating objects to attract schools of tuna.

Seasonal availability

• Mostly caught from May to October, but also available year-round ^[10]

Regulatory and managing authority

• Internationally overseen by the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC). ^[10]
• Along the Pacific West Coast, the fishery is overseen by NOAA fisheries and, as established by the Magnuson-Stevens Act, the Pacific Fishery Management Council  through the West Coast Highly Migratory Species Fisheries Management Plan. ^[10]
• As established by the Marine Life Management Act, the California Department of Fish and Wildlife (CDFW) collects data on this fishery through the Pelagic Fisheries and Ecosystems Program. ^[19,20]

Gear type

• Primarily caught by purse seines. ^[6]
• Fishing gear is selective and allows for the live release of any unintentionally caught species. ^[1]

Status of the fishery

• Declared overfished and subject to overfishing by NOAA; overall decrease in population size since the 1950s; recently assessed at less than 6% of historic levels. ^[7,8]
• There is some controversy over whether or not this species is under threat of extinction, as the IUCN listed this species as 'Vulnerable' in 2014, while a 2017 NOAA study declared the species to be of low risk for extinction. ^[4,7,8]
• Due to concerns about overfishing, regulations now require a permit to harvest, annual quotas or subquotas, gear restrictions, time and/or area closures, and minimum size limits. ^[3,1]
• Bluefin tuna aquaculture has started in other regions, but not in California. ^[13]

Potential ecosystem impacts

• Fishery is subject to risks of bycatch associated with purse seine and longline gear types. ^[6,12]
• Currently, the impact of overfishing and aquaculture for this species on the pelagic food web is not well understood. [13]

Pacific bluefin tuna is typically eaten raw in sushi and sashimi.

Edible portions

• Similar to beef, different cuts of bluefin tuna meat have different names and prices. Because bluefin tuna consumption originated in Japan, these names are in Japanese. ^[14]
• The more common and lower-valued cuts are called akami, while the more expensive, fattier cuts are called toro. The most well-known cuts are otoro and chutoro, which come from the lower belly to the head and the belly at the center and rear, respectively. ^[14] 

Description of meat

• Bluefin tuna is a deep red color when raw, has a high fat content, and has the firmness and appearance of beef steaks. ^[10,14]

Culinary uses 

• Typically served raw in sushi and sashimi, and cooking is generally not advised. ^[10]

Nutritional information 

• Considered an oily fish when raw, and is a good source of protein, thiamin, selenium, vitamin B6, and omega-3 fatty acids. ^[10]
• Nutritional information for 100g raw bluefin tuna on table. ^[10]

Seasonal availability 

• This fish is available year-round, but most are caught in between May and October. ^[10]