Pacific Bigeye Tuna

Pacific Bigeye Tuna

Thunnus obesus

ALSO KNOWN AS:

    Bigeye, `Ahi, Mabachi

SOURCE:

    U.S. wild-caught from Hawaii, California, U.S. Pacific Island territories, and the high seas
 

STATUS

  • POPULATION
  • FISHING RATE
  • HABITAT IMPACTS
  • BYCATCH
 

Click the icons to learn more about each criteria

 
 

OVERVIEW

Measuring a bigeye tuna.

Measuring a bigeye tuna.

LAUNCH GALLERY

Bigeye tuna is a “highly migratory species” – these fish are found around the world and can travel across an entire ocean. Unlike non-migratory species that are only found off our coasts, U.S. fishermen are not the only ones fishing for highly migratory species. Fisheries for species such as bigeye tuna require cooperative international management to ensure the resource is abundant and global harvests are sustainable. The United States is a member of the organizations responsible for the international conservation and management of tuna and tuna-like species in the Pacific Ocean. Domestic management is guided by our participation in these organizations. The United States has implemented both domestic and international measures to control and reduce global harvests of bigeye tuna, and to minimize tuna fisheries’ impact on other species. U.S. fishermen responsibly harvest bigeye tuna under these regulations.

Almost all of the U.S. commercial harvest of bigeye tuna comes from the Pacific (the Atlantic fishery is small). About half is caught incidentally by the purse seine fishery targeting skipjack throughout the tropical eastern Pacific; this catch is canned along with skipjack and yellowfin and sold as “light” tuna. The Hawaii longline fishery harvests the other half. A small amount of this fresh catch is exported; the remaining fresh supply is sold in U.S. markets. U.S. West Coast–based commercial fisheries no longer harvest much tropical tuna (yellowfin, bigeye, and skipjack) — less than 1 percent of the eastern Pacific-wide catch.

Looking Ahead

One of the main challenges for management is continuing to push for measures in the appropriate international organizations to end overfishing of bigeye tuna in the Pacific Ocean. The United States is also focused on ensuring that other countries are implementing and enforcing the measures that are agreed upon in international arenas.

 
 
 

LOCATION & HABITAT

Bigeye tuna are found throughout the Pacific, Atlantic, and Indian Oceans. In the Pacific, they’re more abundant in the western and eastern Pacific than in the central Pacific. In general, they favor clean, clear oceanic waters between 55 and 84 degrees Fahrenheit.

Bigeye tuna are a “highly migratory species,” swimming long distances throughout the ocean. Juvenile and small adult bigeye tuna school at the surface, sometimes with skipjack and juvenile yellowfin tunas. Schools may associate with floating objects or large, slow-moving marine animals such as whale sharks or manta rays. Bigeye tuna also group together near seamounts and submarine ridges.

 
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BIOLOGY

Bigeye tuna grown fast and can reach about 6.5 feet in length. They live 7 to 8 years and are able to reproduce when they’re 3 years old. Bigeye tuna spawn throughout the year in tropical waters and seasonally in cooler waters. They’re able to spawn almost daily, releasing millions of eggs each time. Eggs are found in the top layer of the ocean, buoyed at the surface by a single oil droplet until they hatch.

Bigeye tuna feed near the top of the food chain, preying on fish, crustaceans, and squid. They’re also prey for many top predators including larger tunas and billfish.

 
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PHYSICAL DESCRIPTION

Bigeye tuna are dark metallic blue on the back and upper sides and white on the lower sides and belly. The first fin on their back is deep yellow, the second dorsal and anal fins are pale yellow, and the finlets are bright yellow with black edges.

Bigeye and yellowfin tuna look fairly similar. In fact, it’s hard to distinguish the two species without experience. Among other characteristics, the bigeye’s eyes are larger than the yellowfin’s and their finlets have black edges.

 
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OVERVIEW

The Inter-American Tropical Tuna Commission disclaimer assesses the status of eastern Pacific bigeye tuna every 1 to 2 years. The Western and Central Pacific Fisheries Commission’s disclaimer Scientific Committee regularly assesses the status of western and central Pacific bigeye tuna.

 
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POPULATION STATUS

There are two stocks of bigeye in the Pacific – the western/central Pacific stock and the eastern Pacific stock. In general, although the Pacific-wide population is not overfished, the latest stock assessment (2011) found that fishing rates are too high.

Since hitting a low in 2004, the eastern Pacific bigeye stock has been increasing in abundance and is now above target population levels, partly due to international tuna conservation measures, which established time/area closures for the purse seine fleets and instituted catch quotas in the longline fleets.

The western and central Pacific bigeye stock has declined over the past few decades. The population will continue to decline if both domestic and international fishing rates are not reduced.

 
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ADDITIONAL RESEARCH

Scientists at NOAA’s Pacific Islands and Southwest Fisheries Science Centers monitor tuna fisheries and conduct research on tunas and other animals caught as bycatch in those fisheries.

 
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Harvesting Pacific Bigeye Tuna

Bigeye tuna are an important part of the tuna fisheries throughout the Pacific Ocean and are caught by both surface and deeper longline gears. There are two stocks of bigeye in the Pacific – the western and central Pacific stock and the eastern Pacific stock. In the western and central Pacific, large distant-water longline fleets from Japan and Korea and smaller, fresh sashimi longline fleets based in several Pacific Island countries harvest the majority of bigeye tuna. In the eastern Pacific, the commercially important tropical tuna species (yellowfin, bigeye, and skipjack) are mainly harvested by vessels from the Central and South American fishing fleets.

U.S. commercial fishermen harvest bigeye tuna incidentally in the purse seine fishery and with deep-set pelagic longlines on the high seas. Other domestic fisheries harvest smaller amounts of bigeye tuna. Although none of these fishing gears typically impact habitat, purse seines and longlines sometimes incidentally catch other marine species. Many purse seine fishermen use fish aggregating devices (FADs) to target tunas. FADs are natural floating or man-made objects that are found or placed on or near the ocean surface and used to attract schooling fish underneath. However, FADs can also attract non-target and bycatch species, including juvenile tunas, sharks, other fish, and occasionally protected species. Bycatch of juvenile yellowfin and bigeye tuna is the most significant issue in the purse seine fishery. In the eastern Pacific and western and central Pacific, purse seiners are prohibited from fishing in certain areas and with FADs at certain times of the year to regulate fishing effort and reduce bycatch of juvenile tunas. Fishermen are also required to retain all tuna caught in the purse seine fishery. This measure is partly intended to encourage fishermen to target larger, more profitable adult tunas, rather than juvenile tunas (they are prohibited from discarding juvenile tunas to make room in their fish holds).

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. Management restricts the type of fishing gear that can be used and prohibits fishing in certain areas to minimize impacts on protected species. In addition, longline fishermen are trained in safe handling and release techniques for sea turtles, seabirds, and marine mammals and 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.

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Management

Although NOAA Fisheries and the fishery management councils manage our bigeye tuna fisheries domestically, fisheries for highly migratory species such as bigeye require cooperative international management to ensure they are sustainable.

Who’s in charge? The United States is a member of the Inter-American Tropical Tuna Commission (IATTC) disclaimer and the Western and Central Pacific Fisheries Commission (WCPFC), disclaimer both of which are responsible for the international conservation and management of tuna and tuna-like species in the Pacific Ocean. NOAA Fisheries and the Pacific and Western Pacific Fishery Management Councils disclaimercollaborate in the management of our domestic bigeye fisheries. Domestic management is guided by our participation in the Commissions. Terms of the South Pacific Tuna Treaty also apply to U.S. purse seine vessels operating throughout the central and western Pacific.

Current management: Highly Migratory Species Fishery Management Plan.

  • Permitting, logbook, and monitoring requirements.
  • Gear restrictions and operational requirements to minimize bycatch.
  • Longline vessels and large purse seine vessels on the U.S. West Coast require 100 percent observer coverage. All other purse seine vessels must carry a fishery observer, if requested by NOAA Fisheries.
  • Longline fishing prohibited within 200 miles of the U.S. West Coast.
  • Mandatory annual protected species workshops for all longline vessel owners and operators.

Fishery Ecosystem Plan for Pelagic Fisheries of the Western Pacific disclaimer

  • Permitting, logbook, and monitoring requirements.
  • Gear restrictions and operational requirements to minimize bycatch.
  • Limited entry permit program for Hawaii and American Samoa longline fisheries to control the number of vessels fishing.
  • Longline fishing prohibited areas around the Main Hawaiian Islands, Northwestern Hawaiian Islands, Guam, the Northern Mariana Islands, and American Samoa to protect endangered Hawaiian monk seals, and reduce potential gear conflicts and localized stock depletion (when a large quantity of fish are removed from an area). These zones are enforced through NOAA Fisheries vessel monitoring system (VMS). Longline boats must be equipped with a satellite transponder that provides real-time position updates and tracks vessel movements.
  • Hawaii and American Samoa–based longline vessels must carry onboard observers when requested by NOAA Fisheries, in part to record any interactions with sea turtles, seabirds, and marine mammals. Tuna longline vessels are required to have 20 percent observer coverage. Purse seine vessels operating under the South Pacific Tuna Treaty (i.e., most of the U.S. purse seiners operating in the Pacific Ocean) are required to have 100 percent observer coverage.
  • Mandatory annual protected species workshops for all longline vessel owners and operators.

The United States has implemented management measures recommended by the IATTC disclaimer to address concerns about the condition of eastern Pacific bigeye tuna, including:

  • Purse seine closures in the eastern Pacific.
  • Required retention of tuna caught in the purse seine fishery.
  • Annual catch limit for bigeye tuna caught in the eastern Pacific by U.S. longline vessels.

The United States has also implemented measures as recommended by the WCPFC disclaimer to address concerns about the western and central bigeye stock, including:

  • Annual bigeye tuna catch limits in the Hawaii tuna (deep-set) longline fishery.
  • Limits on purse seine fishing effort.
  • Limits on the number of vessels participating in other fisheries that take bigeye tuna.
  • Seasonal closure of the purse seine fishery that uses fish aggregating devices.
  • Purse seine requirements to retain catch of tuna species.
  • Annual catch quota for the purse seine fishery.

Under conditions of the South Pacific Tuna Treaty, purse seine vessels operating throughout the central and western Pacific must be registered and are monitored through logbooks, cannery landing receipts, national surveillance activities, and vessel monitoring systems, observers, and port sampling.

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Annual Harvest

The majority of the Bigeye Tuna catch comes from Hawaii-and in 2011, Hawaii commercial fishermen landed over 12.8 million pounds of bigeye tuna. California landed just over 100,000 pounds, and nearly 385,000 pounds were landing in American Samoa.

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Economy

In 2011, Pacific Bigeye Tuna landings were worth more than 53 million dollars.

Bigeye tuna caught in the purse seine fishery is canned along with skipjack and yellowfin and sold as “light” tuna. A small amount of bigeye caught in the Hawaii longline fishery is exported fresh; the remaining fresh supply is sold in U.S. markets, both on the island and mainland.

The United States also imports fresh or frozen bigeye tuna from around the world, mainly from Asia, South America, and Central America.

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RECREATIONAL

Anglers also fish for bigeye tuna in the Pacific Ocean. To fish for bigeye off California, private anglers must carry a state-issued saltwater fishing license and charter vessels must obtain highly migratory species permits. U.S. recreational anglers are allowed to possess a maximum of 10 bigeye tuna per day, and charter vessels must keep logbooks documenting their catch. There are no federal regulations for recreational fishing off Hawaii and U.S. Pacific Island territories; however, local rules may apply.

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OVERVIEW

Bigeye tuna is caught in deeper, cooler water than the other tropical tunas. Bigeye tuna meat has a reddish-pinkish color. It typically has a higher fat content than yellowfin and is preferred by sashimi lovers. The prices paid for both frozen and fresh product on the Japanese sashimi market are the highest of all the tropical tunas. Tropical tuna (like bigeye) caught in the purse seine fishery are often canned as “light” tuna. Bigeye from other fisheries is sold fresh and frozen.

 
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SEASONAL AVAILABILITY

Year-round.

 
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NUTRITION

Tuna is low in saturated fat and sodium and is rich in niacin, vitamin B6 and B12, selenium, and phosphorous.

Servings 1
Serving Weight 113 g
Calories 130
Protein 27 g
Fat, total 2 g
Saturated fatty acids, total 0.5 g
Carbohydrate 0 g
Sugars, total 0 g
Fiber, total dietary 0 g
Cholesterol 45 mg
Selenium 160% daily value
Sodium 70 mg

Pacific Bigeye Tuna Table of Nutrition

 
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RECIPES

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