Bluefin tuna, one of the mackerel family in the suborder Perciformes of the class Scleractinian fishes, is widely distributed in the Pacific Ocean and the Atlantic Ocean of the Northern Hemisphere, with a habitat depth of 0-9850 meters and a body length of up to 458 centimeters. It is an oceanic migratory fish, active in schools and carnivorous, feeding on fish, cephalopods and crustaceans, and can be used as food fish, swimming and fishing, and fish breeding.
Characteristics
Bluefin tuna is generally about 200 centimeters in length, up to 458 centimeters, and weighs about 150 kilograms, up to 684 kilograms. The bluefin tuna is a very large species, with the highest point of the body near the center of the base of the first dorsal fin. The second dorsal fin is higher than the first; the pectoral fins are very short, less than 80% of the head length. Has swim bladder. Gill rakers 34-43. Lower side and ventral surface silvery-white with colorless with columns of colorless dots alternating with transverse tangents. The first dorsal fin is yellow or blue; the second reddish-brown; the anal and anal fins are dark yellow and have black edges; the central caudal keel ridge is black when the fish is adult.
The North Pacific bluefin tuna is almost identical in appearance to the Atlantic tuna, and some authorities thought they belonged to two separate populations. However, recent genetic analyses suggest that the two stocks are best considered full stocks. Because this two stocks have not been confused, they are managed as separate stocks.
Range
Bluefin tuna is widely distributed in the Pacific and Atlantic waters of the Northern Hemisphere and can be divided into two subspecies, the Atlantic subspecies and the Pacific subspecies. Atlantic distribution: Western Atlantic: Canada, the Gulf of Mexico, the Caribbean Sea to Venezuela and Brazil; Eastern Atlantic: Norway off the Lofoten Islands to the Canary Islands, including the Mediterranean Sea and the southern part of the Black Sea, and there is also a subpopulation of the distribution of South Africa off the coast of South Africa, is a highly migratory species.
North Pacific bluefin tuna live in Japan and the Philippines, and are found in Honshu in the southern part of the Sea of Japan, and off the coasts of the East China Sea, South China Sea, and Taiwan. Most females may lay as many as one billion eggs. Juveniles move northward in response to ocean currents. Some juveniles migrate eastward to the Pacific coast of North America to breed in the western Pacific Ocean. Most tuna make the return trip at 2 years of age, and some return after a much longer period of time.
Life habits
Bluefin tuna is an oceanic migratory fish, seasonal close to the coast, generally living in 0-100 meters of seawater, the maximum depth of up to 985 meters, the temperature range: 3 ℃ -30 ℃, the activity of the group, the fish according to the size of the group, sometimes accompanied by the barred skipjack tuna, yellowfin tuna, bigeye tuna, longitudinal band _ and other predators of small group swimming fish or squid and red crabs. They can reach speeds of up to 70 kilometers per hour, but usually swim slowly, only 2-3 kilometers per hour. They are carnivorous and feed on fish, cephalopods and crustaceans. The main competitors for food are marine mammals and other large fish, especially other mackerel and sailfish.
Growth and reproduction
Bluefin tuna are ovoviviparous. In the Atlantic Ocean, spawning areas are found in only two regions: the Mediterranean Sea and the Gulf of Mexico. In the Pacific, spawning areas are found in the Philippines. This is a limited spawning area compared to other tropical tunas. Little is known about bluefin tuna spawning because it has not been observed. Spawning occurs from April to June in the Gulf of Mexico and from June to August in the Mediterranean. The differences in timing may be due to a number of factors, such as different environmental factors or genetic variation. In the Gulf of Mexico, spawning occurs at temperatures ranging from 76.8 to 85.1°F (24.9-29.5°C), while in the Mediterranean it occurs at 66 to 70°F (19°C).
Generally, bluefin tuna reach sexual maturity in 3 years, however, it is also thought that bluefin tuna reach sexual maturity in 4-5 years. Females produce an average of up to 10 million eggs per year. Their eggs are buoyant and distributed over considerable distances by surface currents. The larvae hatch to a size of 3.0 millimeters. They have large heads and jaws, and their bodies lack pigmentation. Larval tuna species are difficult to distinguish, however only bluefin tuna have dorsal tail pigmentation. The larvae grow 1 millimeter per day. In spawning areas, larval numbers range from 0.1 to 1.0 per square yard. Young weigh between 40 and 80 kilograms and will separate into populations based on size. These populations are usually composed of multiple species and may contain albacore, yellowfin tuna, bigeye snapper, swordfish, flat ruddered skipjack tuna, skipjack tuna, and golden Spanish mackerel.
Protection level
The IUCN Red List is classified as: Critically Endangered (CR).
The bluefin tuna fishery is very tight at the end of May because the purse seine fleet fishery will officially open, according to a report by Search Fisheries.
Spain is the EU's largest fishery for bluefin tuna, with 2,411 tons of the entire EU quota of 12,900 tons of bluefin tuna,*** and 178 vessels licensed to fish for the species. However, several species of fish in the mackerel family, including tuna, mackerel and marlin, are facing threats to their survival out of 61 known species. The study points to severe overfishing of some species and the neglect of conservation measures for bluefin tuna because of its high commercial value.
Experts warned that three bluefin tuna species, the southern, Atlantic and Pacific bluefin tuna, are in danger of extinction due to overfishing because of their high commercial value, with the southern and Atlantic bluefin tuna on the brink of extinction. The bigeye tuna is also a vulnerable species, and the yellowfin and albacore tuna are also close to the endangered extinction level and will face extinction if protection measures are not adequate. In terms of other species, the blue and white marlin are also assessed as endangered, with the potential for global extinction.
The new study says the only way to save the southern and Atlantic bluefin tuna is to ban fishing until their populations recover, although doing so would cause an increase in illegal fishing.
Conservation measures
Bluefin tuna is one of the most popular food fish. Today the global population of bluefin tuna has been greatly reduced due to slow growth and overfishing. European Union fisheries experts have warned that bluefin tuna could become extinct if fishing is not restricted.
Monaco proposed in July 2009 to list Atlantic bluefin tuna as an object of protection in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The proposal was immediately supported by EU countries including France, Britain, the Netherlands, Germany and Austria. EU countries will discuss the proposal on August 21 to harmonize positions within the EU on the protection of Atlantic bluefin tuna.
The European Commission's commissioner for the environment, Timas, said the European Commission's stance meant that the EU had "taken an important step forward on the road to protecting Atlantic bluefin tuna." French President Nicolas Sarkozy said, "This is a great responsibility for us, and future generations will judge it."
Under the plan, the First Committee of the Conference of the Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) voted on March 18, 2010, and voted down a proposal to ban international trade in Atlantic and Mediterranean bluefin tuna. Japan, a major consumer of bluefin tuna, was "relieved" at the news; animal protection organizations and supporters of the proposal, such as the United States and the European Union, expressed disappointment.
The World Conservation Union lists the southern bluefin, a cousin of the Atlantic bluefin, as critically endangered, the highest level of endangered species in the wild, with the panda, by the way, being one level lower. Oceanographer Schaffner called the Atlantic bluefin the world's "worst victim of deliberate mismanagement".
Trends
The U.S. Tropical Tuna Commission reported in 2001 that because recent catches of bluefin tuna in the northern Pacific Ocean had not declined, it could be assumed that the stock remained stable. However, the average recovery yield of juvenile (age 0--1) tuna, which are heavily fished off Japan, has declined significantly throughout the northern Pacific.
After World War II, with the development of fishing and freezing technology, the ocean became a hunting ground for humans.
Around 1960, the U.S. trawled for large numbers of Atlantic bluefin for canning, resulting in a greatly reduced population of juvenile bluefin.
In 1972, Japan began to send frozen Atlantic bluefin (then worth only a few cents a pound) home from the United States and Canada by airplane, to great acclaim.
In 1989, the Atlantic bluefin population was down to 20 percent of what it was in 1970, and today it's down to 10 percent.
The global catch of bluefin tuna in 2006 was at least 30 percent over the limit.
Fishing season
In the Western Pacific, North Pacific bluefin tuna can be caught year-round.
In the eastern Pacific, on the other hand, North Pacific bluefin tuna can be caught in the summer and early fall only off the west coast of the United States and Mexico.
Catch records
In 1864, fishermen on the Italian island of Favignana recorded 14,020 bluefin tuna, weighing an average of 192 kilograms each, and in 2009 the catch was only about 100, averaging 29 kilograms, a true record of the bluefin tuna tragedy.
Adult stocks caught on longlines from the 1950s to the mid-1980s were already on the decline. But part of that decline may have been due to changes in migratory patterns.
Catches in the eastern Pacific Ocean were low between 1980 and 1990, but the Bellew regulations (1991) ruled out overfishing as the cause and attributed the migration of juvenile tuna from the west to the east during this decade to changes in their oceanographic conditions.
In 1991, the yield analysis suggested that the western and eastern fisheries would benefit from harvesting small numbers of juveniles to improve the age structure of the fishery. However, these models were hampered by incomplete age-structure data and the absence of reliable estimates of natural mortality for the stock.
After 2011, the harvest of juvenile fish continues to affect the fishery. Bellew's Law was noted in 2001, and yield and cohort analyses indicate that more catch could be made if the catch of age-0 and age-1 bluefin tuna were reduced or eliminated. The National Marine Fisheries Service (NMFS) draft fishery management plan for 2001 states, "The impacts of exploitation remain uncertain because the key rates for bluefin tuna are poorly known. No reliable relative rates of biomass and fishing mortality (maximum sustainable yield) have been determined."
January 5, 2011 marked the first trading day of 2011 at the nation's major wholesale markets specializing in fresh foods such as fish, fruits and vegetables in Japan. At the Tsukiji market in Tokyo, a bluefin tuna from Toei, Hokkaido, became the current "Nippon Ichi" (Japan's No. 1 tuna) with a weight of 342 kilograms. Eventually it was a high-class sushi restaurant owner in Ginza, Tokyo, Imada Yosuke and Hong Kong, a sushi restaurant chain owner Zheng Weitao joint auction, the price of 32.49 million yen, the fish will be divided equally between the two. The auction set a record for the highest auction price for a single tuna. Tsukiji market said this is the highest price for a single tuna since 1999, when Japan began to count the price of tuna, breaking the record set in 2001, when the "Nippon Ichi" sold for 20.2 million yen, and the first time that Hokkaido's Togai-produced tuna has fetched an all-time high price.
January 5, 2013 Japan's NHK TV news said, in the early morning of the 5th in Japan's largest fish market in Tokyo Tsukiji market, a sushi restaurant to 155 million yen (about 10 million yuan) to buy a 222kg tuna, the price also broke the record for the highest price, creating a new record.
On January 6, 2014, the first auction of bluefin tuna in Tsukiji, Tokyo, was sold for 7.36 million yen:2014's first bid. A 230-kilogram bluefin tuna from Oma, Aomori Prefecture, sold for 7.36 million yen (about 425,000 yuan, or 32,000 yen per kilogram), about one-twentieth of the 2013 top price. The winning bidder was Kiyomura, which operates a chain of sushi restaurants.
In April 2014, 56-year-old fisherwoman Donna Pascoe caught an 823-pound Pacific bluefin tuna, a record-breaking fish twice the size of a baby elephant.
On May 11, 2014, Shanwei fisherman Ah Hong caught a 680-pound suspected bluefin tuna 60 kilometers offshore of Huidong, Huizhou, and a Huidong netizen drew crowds of spectators by posting pictures of the big fish. Ahong said he had caught such a big fish for the first time in his 20 years of fishing experience. Li Huiquan, chief engineer of Guangdong Provincial Marine and Fishery Resources Monitoring Center, also introduced that the tuna is more likely to be bluefin, and such a huge tuna caught in Huizhou waters is the first time he has heard of it in his 30 years of experience.
July 13, 2014, on the coast of Cornwall, England, five college girls picked up a precious bluefin tuna. This tuna body two meters weighs about 272 pounds, the market value is worth nearly 7 million yuan.