One of the main challenges for managers is continuing to limit bycatch and non-target catch in the purse seine fishery that uses fish aggregating devices (FADs) while maintaining current levels of catch of skipjack. This requires collaboration among scientists, managers, and the fishing industry to develop new gear technologies and fishing and marketing strategies.
- Ocean perch
- Sea Bass
- Turbot (Greenland)
Pacific Skipjack Tuna
ALSO KNOWN AS:
Ocean Bonito, Lesser Tuna, Aku, Katsuo
U.S. wild-caught from waters of non-U.S. Pacific Island countries and the high seas, as well as U.S. Pacific Island territories, Hawaii, and California
- FISHING RATE
- HABITAT IMPACTS
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School of skipjack tuna.LAUNCH GALLERY
Skipjack tuna is a “highly migratory species” – these fish are found around the world and can travel across an entire ocean basin. Unlike non-migratory species found only off our coasts, U.S. fishermen aren’t the only ones fishing for highly migratory species. Fisheries for species such as skipjack 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 global tuna harvests and to minimize tuna fisheries’ impact on other species. U.S. fishermen responsibly harvest skipjack tuna under these regulations.
Almost all of the U.S. commercial harvest of skipjack tuna comes from the western and central Pacific near the Equator. U.S. fisheries catch about 9 percent of the total skipjack harvest in the Pacific. (In the Atlantic, annual skipjack tuna harvests make up a small percentage of the Atlantic tunas brought to port by U.S. fishermen and an even smaller percentage of the Atlantic skipjack tuna harvested worldwide.) Much of the U.S. harvest is exported to foreign canning markets. Most of the canned “light” tuna (which includes skipjack) for sale in the United States is imported, mainly from Thailand, the Philippines, Indonesia, and Ecuador.
LOCATION & HABITAT
Skipjack tuna are found in tropical, subtropical, and warm temperate waters of all oceans. In the eastern Pacific, they’re found from Vancouver Island, British Columbia, to Peru; in the western Pacific they’re found from northern Japan to southern Australia.
Skipjack tuna are a pelagic species – they mostly live in the open ocean, although they may spend part of their life in nearshore waters. They can be found in large schools swimming in warm, well-mixed surface waters and to depths of 850 feet during the day. They generally stay near the surface at night. Skipjack tuna is a highly migratory species, swimming long distances to feed and reproduce.
Like other tropical tunas, skipjack tuna grow fast, up to nearly 4 feet and over 70 pounds, and have a short life span compared to other temperate tunas, around 8 to 12 years. In the Pacific, skipjack are able to reproduce when they reach about 1.3 feet in length. They spawn throughout the year in tropical waters and seasonally (spring to early fall) in subtropical waters. Depending on their size, females produce between 100,000 and 2 million eggs each time they spawn. Once fertilized, the eggs hatch in about 1 day, depending on temperature. Skipjack spawn more than once a season, and some spawn almost every day.
Skipjack tuna are opportunistic feeders, preying on a variety of fish, crustaceans, cephalopods, and mollusks. Cannibalism is also common. Large pelagic fishes such as billfish, sharks, and other large tunas prey on skipjack tuna.
Skipjack tuna do not have scales except on the corselet and the lateral line. (The corselet is a band of large, thick scales forming a circle around the body behind the head and extending backwards along the lateral line. The lateral line is a faint line running lengthwise down each side of the fish.) Their back is dark purplish-blue, and their lower sides and belly are silvery with 4 to 6 conspicuous dark bands that run from behind the head to the tail, which may look like a series of dark blotches.
The Western and Central Pacific Fisheries Commission regularly assesses the status of the western and central Pacific skipjack tuna stocks, and the Inter-American Tropical Tuna Commission assesses the eastern Pacific stocks.
Skipjack tuna is a notoriously difficult species to assess. Due to skipjack’s high and variable productivity, it’s difficult to determine the effect of fishing on the population using standard fisheries data and stock assessment methods. Assessments are particularly difficult for the eastern Pacific stock due to limited data. Because of these difficulties, the status of the eastern Pacific stock is largely based on indices of abundance and the biological characteristics of the species (fast growing, etc.). Scientists are fairly certain the stock is abundant and is being fished at sustainable levels, but this is not based on a full stock assessment.
In the western and central Pacific, abundance estimates are well above the target level. Scientists believe this stock is being fished sustainably, but caution that they need additional data to address uncertainties in the relationships between the various abundance indicators used in skipjack tuna stock assessments.
Scientists at NOAA’s Southwest and Pacific Islands Fisheries Science Centers contribute to research on Pacific tropical tunas including skipjack by monitoring U.S. fisheries, conducting stock assessments, and participating in international forums for the assessment of these species.
Harvesting Pacific Skipjack Tuna
Skipjack tuna is a highly migratory species that travels throughout large areas of the Pacific. There are two stocks of skipjack tuna in the Pacific Ocean, one in the western and central Pacific and one in the eastern Pacific. In the western and central Pacific, skipjack tuna are harvested in a variety of fisheries, from small-scale artisanal fisheries in Pacific Island and southeast Asian waters to large, distant-water purse seiners operating in waters near the Equator. Distant-water fleets from Japan, Korea, Taiwan, and the United States capture most of the skipjack harvested in the western and central Pacific. Much of the U.S.-caught skipjack from this area is harvested by purse seiners based in American Samoa. Skipjack tuna is also caught in the Pacific Islands troll fisheries and the Hawaii-based longline, pole-and-line, and troll fisheries.
In the eastern Pacific, skipjack tuna are primarily harvested by purse seine vessels from Central and South American countries. The U.S. purse seine fleet operating in the eastern Pacific is small. Small purse seiners fishing off California for small pelagic species such as sardine and anchovy sometimes will also target skipjack tuna when warm water from the south brings the species within their range.
While 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 in the western and central Pacific, purse seiners are prohibited from fishing in certain areas 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 (as the measure prohibits them 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.
Although NOAA Fisheries and the fishery management councils manage our domestic skipjack tuna fisheries, fisheries for highly migratory species such as skipjack tuna 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 and the Western and Central Pacific Fisheries Commission, 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 collaboratively manage our domestic skipjack fisheries. Domestic management is guided by our participation in the two Commissions. Terms of the South Pacific Tuna Treaty also apply to U.S. purse seine vessels targeting tuna throughout the western and central Pacific.
- Fishermen must have a permit to harvest tuna and must keep logbooks \ documenting their catch.
- Gear restrictions to minimize bycatch.
- Large purse seine vessels on the U.S. West Coast required to have 100 percent observer coverage. All other purse seine vessels must carry a fishery observer, if requested by NOAA Fisheries.
- Fishermen must have a permit to harvest tuna and must keep logbooks documenting their catch.
- Gear restrictions and operational requirements to minimize bycatch.
- If requested, vessels are required to carry a NOAA Fisheries–certified observer to collect scientific data. 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.
The United States has implemented conservation and management measures adopted by the Western and Central Pacific Fisheries Commission to control juvenile tuna catch in the purse seine fishery targeting skipjack and to minimize impacts to non-target species such as sea turtles and sharks. These measures include:
- Limits on the number of days purse seiners can spend fishing in certain areas.
- A seasonal prohibition on the use of fish aggregating devices by purse seine vessels.
- Closure of specific high seas areas in the western and central Pacific to purse seine vessels.
- A requirement for purse seine vessels to retain certain tuna species.
- Purse seiners fishing in the Commission’s management area must also carry a fishery observer and must follow specific handling requirements in case they accidentally catch a turtle.
The United States has also implemented conservation and management measures adopted by the Inter-American Tropical Tuna Commission to control effort in the tuna purse seine fishery and reduce impacts to other species such as sea turtles, sharks, seabirds, and juvenile tunas. These measures include:
- Time/area closures to reduce the catch of juvenile tunas.
- Required retention of tuna caught in 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, vessel monitoring systems, observers, and port sampling.
Most of the global harvest of skipjack tuna in the Pacific Ocean comes from the western and central Pacific. U.S. fisheries account for about 9 percent of this harvest. In 2010, Hawaii-based fishermen landed close to 300,000 pounds of skipjack; American Samoa–based fishermen landed more than 243,000 pounds of skipjack.
Much of the U.S. harvest (mostly caught by American Samoa–based purse seiners) is canned in American Samoa or exported to foreign canning markets. West Coast–based commercial fisheries no longer harvest large numbers of tropical tunas – now less than 1 percent of the total eastern Pacific–wide catch – because U.S. canning facilities have relocated overseas to take advantage of cheaper labor markets. Some of the skipjack that is harvested is frozen and exported to other countries, including New Zealand, Russia, and Spain.
The United States also imports fresh and frozen skipjack tuna to supply U.S. canneries, mainly from China, Mexico, and the Philippines. Most of the canned tuna for sale in the United States is imported; the United States imports “canned light tuna” (which includes skipjack) mainly from Thailand, the Philippines, Indonesia, and Ecuador.
Recreational anglers also fish for skipjack tuna. Off the West Coast, anglers must have the appropriate licenses and permits to catch highly migratory species such as skipjack. There are no federal regulations for recreational fishing off Hawaii and U.S. Pacific Island territories; however, local rules may apply.
Skipjack tuna are primarily sold as “canned light tuna” (often packed along with yellowfin tuna) but are also sold fresh or frozen. When raw, good-quality skipjack tuna meat is deep red. Smaller fish are lighter red. Cooked skipjack becomes light gray. Skipjack tuna has the most pronounced taste of all of the tropical tunas.
Skipjack is an excellent source of low-fat protein.
|Serving Weight||100 g (raw)|
|Fat, total||1.01 g|
|Saturated fatty acids, total||0.328 g|
|Sugars, total||0 g|
|Fiber, total dietary||0 g|
Pacific Skipjack Tuna Table of Nutrition