Atlantic bluefin tuna
The Atlantic bluefin tuna is one of the most iconic fish species in the world. They are known for being large, beautiful, strong swimmers that can live up to 80 years old. But what do you know about the scientific classification of the Atlantic bluefin tuna? What does it mean to be classified as a “Thunnus?” And how did the binominal name come into existence?
Atlantic Bluefin Tuna – Scientific Classification
Scientific Classification of Atlantic Bluefin Tuna
Atlantic Bluefin TUNA
What Is A Thunnus?
A Thunnus is an order of fishes within the class Osteichthyes. The order includes all bony fishes (including sharks and rays) and some cartilaginous fishes (such as dolphins). There are currently around 1,500 different species of fish in this group.
The word “Thunnus” comes from the Greek words thunna meaning “tocut or divide” and ous meaning “fish”. This means that the word “Thunnidae” literally translates to “the family of fish with cutting fins”.
The Atlantic bluefin is also called the “true tunny” because they belong to the genus Thunnus. In fact, there are two other genera of tunnies: Thynnus and Euthynnus. However, these three genera are not closely related to each other.
The Atlantic bluefin belongs to the subfamily Thunninae which contains only four species of tunnies. These include the Pacific bluefin tuna, the Japanese skipjack tuna, the yellowfin tuna, and the bigeye tuna.
The Atlantic bluefin tuna (Thunnus thynnus) was one of the many species originally described by Swedish naturalist Carl Linnaeus in the 10th edition of his seminal workSystema naturae, published in 1758. He gave it the binomial name Tux thunni; the specific epithet thynnus means “of the sea”. In the same volume he described the Pacific bluefin tuna and several other species of tuna, along with some smaller fishes.
Linnaeus’ description of the Atlantic bluefin tuna was based on specimens collected off Sweden and Denmark. His account of the species was the first scientific treatment of the subject, predating Johann Georg Gmelin’s 1810 Synopsis methodica animalium marinae sive de aquatibus regionibus ejusdem, which included descriptions of the Atlantic bluefin and the Pacific bluefin.
In the 10th edition, Linnaeus recognized three subspecies of the Atlantic bluefin:
A. thynnus (Linnaeus, 1758): the nominate subspecies, found in the North Sea, Baltic Sea, Kattegat, Skagerrak, Norwegian Sea, Barents Sea, White Sea, Gulf of Bothnia, and Black Sea. This subspecies had been named by Karl Friedrich von Martius in 1844.
B. oceaniensis (Günther, 1861): found in the Mediterranean Sea. Named by Johannes Peter Müller in 1869.
C. tardus (von Siebold, 1848): named by Charles Frédéric Girard in 1851. Found in the Indian Ocean.
Subsequent authors have generally followed Linnaeus’ taxonomic arrangement, though some authorities recognize additional subspecies:
1. thynnus (L.) (Linnaeus,1758)
2. maccullochi (Cuvier, 1830)
3. hansoni (Forsskål, 1775)
4. kobbei (Bleeker, 1860)
5. lanceolatus (Bloch, 1792)
6. japonicus (Temminck & Schlegel, 1850)
7. leucurus (Houttuyn, 1782)
8. macropterus (Risso, 1827)
9. mazatlantensis (Deshayes, 1825)
10. mexicanus (Valenciennes, 1840)
11. nigrescens (Poey, 1860)
12. pinnatus (Sauvage, 1874)
13. ruficaudalis (Steindachner, 1867)
14. schlegeli (Mueller, 1883)
15. sebastianii (Boulenger, 1900)
16. stejnegeri (Regan, 1908)
17. thompsoni (Kishinouye, 1906)
18. zetlandicus (Richardson, 1909)
19. wollebaeki (Jäderholm, 1913)
20. yaluensis (Worthington, 1912)
21. yamashitai (Yamaguchi, 1935)
The Atlantic bluefin is one of the world’s most powerful predatory fishes. Its name is derived from the colour of its flesh; the word ‘blue’ refers to the bluish tint seen in the dorsal surface of the fish.
The species epithet is Latin for ‘big’, referring to the size of the fish. Bluefins are among the fastest swimmers in the ocean, reaching speeds up to 35 km/h (22 mph). They are capable of accelerating rapidly for short distances and can reach cruising speed within seconds. They swim slowly when stationary, but can accelerate quickly when disturbed. Bluefin tuna are highly aggressive towards each other, even while still immature. When adults, they rarely attack unless provoked, although they do sometimes fight with larger predators such as sharks. This behaviour is likely due to the fact that they are usually very old and slow moving compared to their potential prey. However, they are known to occasionally hunt young sharks, possibly because they are easier to catch.
Bluefin tuna grow extremely fast during their early life stages, reaching maturity in about five years. Adult males typically measure 3 metres (9.8 ft) in length and weigh up to 250 kilograms (550 lb), while
Biology and ecology
The Atlantic bluefin tuna typically hunt small fish such as sardines, anchovies and herring. In addition to being a popular food source, the species is also considered an important component of marine ecosystems because it plays a role in maintaining healthy populations of smaller fish. They are known to migrate long distances in pursuit of prey. For example, some individuals travel up to 5,000 km (3,100 mi) during spawning migrations.
Bluefin tuna typically feed on zooplankton, small crustaceans, cephalopods, and bony fishes. Like most tunas, they swim at speeds of around 20–40 km/h (12–25 mph), though occasionally reaching 50 km/h (31 mph). Their maximum speed is about 60 km/h (37 mph), and they usually cruise at 30 km/h (19 mph). A bluefin can weigh up to 2 tonnes (2 short tons; 2 t) and reach lengths of 3 metres (9.8 feet). The average lifespan is 8–10 years.
Bluefin Tuna (Thunnus thynnus) are oviparous, congregating together in large schools called tunaseries to spawn. They are found in temperate waters worldwide; the southern limit of their distribution is the Gulf Stream off the coast of Florida.
Spawning occurs over many days, usually during the summer months, depending upon location. Females release large numbers of eggs into open bodies of water such as bays, estuaries, and coastal lagoons. The number of eggs released varies widely among females, ranging from 2,000 to 50,000. A single female may release as many as 40 million eggs in one spawning event.
The female bluefin tuna spawns every three to four years, and she does it multiple times throughout her life. She typically mates once, although some females mate twice. After mating, the female lays approximately 80,000 eggs, each weighing less than half an ounce. Each egg hatches within 48 hours of being laid, and the larvae take two weeks to develop into juvenile fish.
Juvenile bluefin tuna live in small groups known as “schools”, each school consisting of 25–50 individuals. School sizes vary greatly, from just a few fish to hundreds of fish. Schools of bluefin tuna migrate seasonally, following prey species, and often.
Schools of bluefin tuna have been observed to follow schools of schooling fish such as mackerel or sardines. During migration, bluefin tuna will form large aggregations, which are referred to as tunasheries. These aggregations are composed of thousands of individual fish. Tunasheries are generally located near feeding grounds, where the fish feed on planktonic organisms such askrill, copepods, and larval fish.
Tunas mature sexually when they are between five and seven years old. Most bluefin tuna do not breed until they are eight to ten years old. However, there are exceptions. Some bluefin tuna that are caught early in their lives may be immature males who were captured while still migrating with their mothers. Other bluefin tuna maybe mature females who were born prematurely.
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Atlantic bluefin tuna are among the most sought-after fish in the world. Their meat is considered one of the best tasting and highest quality seafood products. This deliciousness makes it easy to understand why the Atlantic bluefin tuna population has declined over the past few decades.
The Atlantic bluefin tuna population is now listed as critically endangered by the International Union for Conservation of Nature (IUCN). A recent study published in Marine Policy found that the Atlantic bluefin tuna stock had declined by 90% since the 1970s.
This decline is due to unsustainable fishing practices such as longlining, gillnetting, trawling, bottom trawling, purse seining, drift netting, and illegal, unregulated and unreported (IUU) fishing.
After World War II, Japanese fisherman needed more tuna to feed themselves and to export for European canning industries. To meet demand, they had to expand their fishing range and perfect industrial long-line fishing—a process that involves thousands of baited hooks attached to miles-long lines. In the 1970s, Japan’s manufacturers began developing lightweight, high-strength materials that were spun into drift nets. These nets could withstand the force of ocean currents and waves, allowing fishermen to deploy them over large areas.
At-sea freezing technology then enabled them to bring frozen sushi ready tuna from the furthest oceans to market after as little as one year. By the 1980s, the industry employed tens of thousands of people. But it wasn’t just about quantity; it was about quality too. As demand increased, some fishermen turned to illegal methods like driftnetting, which involved setting long-lines baited with thousands of hooks that dragged along the sea floor. This method was banned on the high seas under the Convention on International Trade in Endangered Species (CITES), but in the late 1970s, hundreds of kilometers of driftnets were often deployed in a matter of nights.
The initial target was yellowfin. Because they are small, fast swimmers, yellowfin are easy prey for larger fish such as blue marlin, swordfish, and sharks. Yellowfins are also highly sought-after because of their rich taste and fat content.
The IUCN Red List of Threatened Species classifies a species as critically endangered, endangered, vulnerable, or near threatened based on how likely it is to become extinct within the next 10–20 years. A species is considered “extinct in the wild” if there are no living individuals left in the wild.
A species is assessed as being “further removed from extinction” if there are still some living individuals remaining in the wild. For example, a species classified as “endangered” could either fall into one of three categories—critically endangered, endangered, or vulnerable—based on whether it faces an extremely high risk of becoming extinct in the wild, a high risk of extinction, or a moderate risk of extinction, respectively.
Bluefins are known for being one of the most voracious predators in the ocean. In fact, they are often referred to as “the world’s greatest scavengers.” This makes sense given how much food they eat. A single bluefin could consume up to 50 tons of prey per day.
They will also filter-feed, meaning they use their mouth to sift plankton and small organisms out of seawater. A bluefin might spend hours swimming around looking for something tasty to chow down on. When it finds something good, it opens its huge mouth wide, filters out the food, and swallows it whole.
Western Atlantic Bluefin Tuna
The western Atlantic bluefin tuna population has been decimated, according to the latest assessment by the International Union for Conservation of Nature (IUCN). This is the second consecutive year the IUCN has downgraded the status of the species to critically endangered due to overfishing. In 2016, the organization listed the western Atlantic stock as being under threat because it had lost 75 percent of its biomass since 1970.
The IUCN report states that the population has declined by 90 percent during the past three decades. There are just 2 million tons left compared to 50 million in 1970. The decline has been attributed to unsustainable fishing practices such as longline and gillnetting. Overfishing has led to depleted stocks of predators like sharks and seabirds, which prey upon fish eggs and larvae.
In addition to the declining numbers, the IUCN says there is evidence that the western Atlantic bluefin population is genetically isolated. This could lead to further declines in the future.
About the Species
The western Atlantic bluefin tuna fishery is one of the most sustainable fisheries in the world. This species is harvested responsibly and carefully monitored by scientists to ensure sustainability. Western Atlantic bluefin tuna are caught primarily in international waters off the coasts of New York, Massachusetts, Rhode Island, Connecticut, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, Texas, Puerto Rico and Bermuda.
The population level is unknown for the western Atlantic bluefin tuna stock. However, there are several estimates of total global catch levels. In 2016, the Food and Agriculture Organization (FAO) reported that the world caught around 50 million tonnes of bluefin tuna. This number included catches from both commercial fisheries and artisanal fishermen. But it did not include illegal fishing activities such as driftnetting.
In 2010, the FAO estimated that the world caught about 55 million tonnes of bluefin. This number includes catches from both commercial fisheries as well as artisanal fishermen.
In 2009, the International Commission for the Conservation of Atlantic Tunas (ICCAT) estimated that the world caught around 70 million tonnes of bluefin that year. ICCAT used data from 2004–2008 to estimate the size of the fish being caught. They assumed that the average weight of each fish was 400 kg.
In 2007, the United Nations Food and Agricultural Organization (UNFAO), along with Japan, Korea, Taiwan, China, Vietnam, Indonesia, Malaysia, Thailand, and the Philippines, estimated that the world caught approximately 85 million tonnes of bluefin in 2005. UNFAO used data from 2000–2006 to estimate the size of each fish being caught. They again assumed that the average weight was 400 kg.
However, none of these numbers take into account the amount of fish that is discarded due to lack of market demand.
The term fishing rate refers to how often you catch fish while fishing. This value represents the number of times you caught a fish per hour of fishing. For example, if you are catching one fish every 30 minutes, your fishing rate is 0.33 fish/hour. If you are catching 10 fish per hour, your fishing rate is 3.0 fish/hour.
Fishing gear used to catch bluefish off the coast of New England rarely touches the ocean floor and has little effect on the environment, according to a study published Tuesday in Scientific Reports. Researchers found that a majority of commercial fishing equipment did not touch the seafloor during its use, meaning it had no significant impact on habitats. The findings are based on surveys conducted over three seasons in 2013, 2014 and 2016. In total, researchers surveyed nearly 500 pieces of fishing gear. They found that about 80% of the nets, traps, lines and hooks never touched the bottom. Only 2% of the gear actually contacted the seabed. Bluefin tuna, one of the world’s most lucrative fish species, is being fished heavily off the Atlantic Coast of North America. But many fishermen don’t follow strict regulations designed to protect the marine ecosystem. This lack of regulation has led to concerns over how much damage the industry causes. Bluefin tuna, once common off the East Coast, now face extinction due to overfishing. Scientists estimate that there are fewer than 10 mature female bluefin left in the Atlantic Ocean. About 70% of the bluefin caught are juveniles, meaning they’re too young to reproduce.
Western Atlantic Bluefin Tuna (Thunnus thynnus) stocks are assessed annually by ICCAT using the Population Viability Analysis (PVA). This analysis uses scientific data and models to estimate fish population growth rates and assess whether the population is likely to recover within the next 10 years. A stock is considered overfished if it cannot reach a target level of abundance. In addition, ICCAT recommends management measures to prevent further decline of the stock.
In June 2018, the Western Atlantic stock assessment reported that the stock had recovered sufficiently since 2006 to return to sustainable levels. Overfished status was removed from the stock. However, the stock continues to face challenges due to high mortality caused by illegal driftnet fisheries operating off the coasts of Florida and Texas.
The stock is now being managed under ICCAT recommendation 20-06, which is based on a recent stock assessment and scientific recommendations. The recommendation provides for annual catch limits ranging from 0.8 million tons to 3.3 million tons per year. These quotas are designed to maintain the current size of the stock while allowing the stock to grow naturally.