One, tuna introduction
Tuna (tuna) is a large pelagic important commercial food fish. It is found in the warm waters of the world, and mackerel, mackerel, horse mackerel and other close relatives, usually under the same mackerel family. There is considerable variation both within the family and between species, and the classification is very variable, with authorities divided on the subject.
Tuna is also known as tuna, or tuna in Hong Kong, and in Macao, it was formerly known as asado in Portuguese, and most of it belongs to the genus Tuna. Tuna's meat color is red, which is due to the large amount of myoglobin contained in the tuna's muscle. Some tuna, such as the bluefin tuna, can utilize the metabolism of the swimming muscles to keep the temperature of the blood in the body higher than the outside water temperature. This physiological function allows the tuna to adapt to a larger range of water temperatures and thus be able to survive in cooler waters.
Tuna swim fast, instantaneous speed of up to 160 kilometers per hour, the average speed of about 60-80 kilometers per hour. Tuna is distributed in the Indian Ocean, the central Pacific Ocean and the middle of the Atlantic Ocean, belonging to the tropical - subtropical oceanic fish. The tuna's swimming range is very far, in the past has been found in the Japanese coastal waters from the United States to swim past the California tuna.
Tuna has six species, most of which are huge, the largest body length of 3.5 meters, weighing 600 to 700 kilograms, while the smallest varieties of only 3 kilograms. Tuna's reproductive capacity is very strong, a 50 kg female, can produce as many as 5 million eggs per year. Tuna is a popular seafood with high economic value. Policies, activities and overfishing by fishermen in various countries have threatened their populations, most notably the bluefin tuna. As a result, international regulation of tuna fishing has begun, but with limited success.
Biological Properties
Chinese Name Tuna
Latin Name Thunnus
thynnus (Linnaeus)
Alias Tuna, Tuna
Archaeopoda
Phylum Chordata
Subphylum Chordata
Subspecies
Subphylum Vertebrata
Organism Scleractinia
Order Perch
Suborder Tuna
Family Tuna
Genus Tuna
English name tuna
Three physical characteristics
Tuna is a long fish with a long body.
The body is long, stout and rounded, streamlined, tapering backward to a fine tip and a slender caudal base, with a forked or crescent-shaped caudal fin. The caudal peduncle has distinct ridges on both sides, and the dorsal and anal fins each have a row of small fins behind them. It has a torpedo body shape with a slightly rounded cross-section. The tuna also has a peculiar shape, with its entirety streamlined and a pectoral armor that extends along the head as if it were a unique balance board capable of adjusting the current. In addition, the tuna's tail is half-moon shaped, enabling it to sprint forward very quickly in the ocean. Strong muscles and a crescent-shaped tail fin, the shoulders have a pectoral armor made up of tapering scales, darker on the dorsal side and silvery white on the ventral side, usually with iridescent rays and stripes. Another feature is a well-developed network of blood vessels under the belly, which serves as a thermoregulatory device for long-distance, slow-speed swimming.
The most massive and rare tuna is the bluefin tuna, also known as the black tuna, which grows to a maximum of about 4.3 meters and 800 kilograms.
Four, classification
Biologically speaking, broadly speaking, tuna refers to the fish family mackerel, swordfish and sailfish family *** counting about 30 species of fish. The species with greater economic value include bluefin tuna, marsupial tuna, bigeye tuna, yellowfin tuna, albacore tuna, skipjack tuna, and six other species:
1. Yellowfin Tuna
(English: Yellowfin Tuna): the body of the fish is fusiform, slightly laterally flattened, the head is small, the tail is long and thin, and the flesh is Pink color. The back of the body is bluish-blue, the side of the body is light gray, with a little yellow, a little transverse band, the second dorsal and anal fins and the small fins behind them of the adult fish, are bright yellow. The first dorsal and ventral fins are tinged with yellow. The length of the body is 1-3 meters, which varies from one sea area to another, and the large ones can reach up to 2 meters and weigh more than 100 kilograms.
The yellowfin tuna has a wide range of diets, with squid, surface fish and large crustaceans dominating. It makes long-distance migrations, and its migrations are related to seasonal changes in sea currents; during the tropical rainy season, it moves away from lighter coastal waters and swims to higher salinity sea areas.
Yellowfin tuna is widely distributed in the equatorial waters of the three oceans of the struggle, is a representative species of the tropical sea area. Yellowfin tuna is common in water depths up to 160 meters, water temperature up to 20-28 ℃, the maximum swimming speed of 90 km / hour.
2. Bluefin tuna
(English: Atlantic bluefin tuna) is the largest species in the tuna group, also known as blackfin tuna. The body is short and sturdy, tapered and elongated, with a crossed caudal fin; the bottom to the side of the body is brightly colored, while the upper body is dark blue, the fins are dark dark, the small fins are yellowish, and the caudal peduncle ridge is black. The entire body is scaled, the mouth is quite large, the eyes are not large, and the pectoral fins are short, ending less than the center of the first dorsal fin, which is the most characteristic feature of this species. The body length is generally 1-3 meters, the larger one is more than 3 meters long, weighing more than 700 kilograms.
Bluefin tuna are often found in schools of 50-60 fish, but there are also schools of more than 1,000 fish. Habitat water layer from the surface to 50 meters deep, the optimal water temperature of 10-20 ℃, bait to herring, sardines, mackerel, squid and crustaceans.
3. Bigeye Tuna
(English: Bigeye Tuna) is also known as fat tuna and parrot tuna, with a body length of about 1.5-2.0 meters, and a large body weight of more than 100 kilograms, generally 160-350 kilograms. The back of the body is blue-green, and the sides and belly are silver-white. The flesh is pink and slightly soft. The pectoral fins are long, with their ends protruding well below the second dorsal fin, which is also narrower and of similar height to the first dorsal fin. The fish is gray, plump, with a short tail and a distinctly larger head and eyes.
The bigeye tuna inhabits deeper water, up to 200-300 meters, and sexually mature individuals inhabit the surface layer. Mainly feed on deep-sea fish, small fish, squid and large crustaceans. The maximum swimming speed can reach 100 kilometers / hour.
4.Masu tuna
(English: Southern
bluefin tuna) Masu tuna, also known as the southern bluefin, southern bluefin tuna, which is a kind of fish living in the ocean's middle and upper waters, distributed in the Atlantic Ocean, the Indian Ocean and the Pacific Ocean in the temperate zone and the cold Ocean, mainly concentrated in the 30 ° S to 50 ° S, close to 60 ° S of the sea, is a highly migratory oceanic fish. The body of the tuna is generally 160 centimeters long, and can reach a maximum length of 245 centimeters and a weight of up to 260 kilograms.
5. Skipjack tuna
(English: Skipjacktuna), also known as skipjack tuna, smoked, small string, firewood, smoked tiger, one of the mackerel family of the suborder Mackerel of the class Perch of the order Orthopterygian finfish. It is distributed in the warm waters of the world's oceans. Body length 40-70 centimeters. The maximum body length can reach 111 centimeters. The maximum weight can reach 34.5 kilograms. The body is fusiform, laterally compressed, the back is pale black, the belly is white, and there are 4-10 longitudinal lines of intense blue color, the mouth is pointed, and most of them are scale-free. It lives in temperate and tropical waters and has seasonal migrations.
V. Distribution
Tuna tuna belongs to the Perch family Mackerelidae, also known as tuna, the Chinese world is also known as "tuna (fish). It is an oceanic warm-water migratory fish, mainly distributed in the low and mid-latitude sea area, in the Pacific Ocean, the Atlantic Ocean, the Indian Ocean are widely distributed. China's East China Sea, the South China Sea is also distributed. With the tuna is most similar to the skipjack tuna fish, the simplest way to distinguish between the skipjack tuna abdomen has 4-6 black longitudinal bands, other similar species such as the rudder skipjack tuna, skipjack tuna, etc. have a dark longitudinal bands and so on. Tuna species, on the other hand, do not have any black spots, or dark longitudinal stripes on the body. The tuna's ventral fins are significantly longer than those of the rudder skipjack and the fox skipjack.
Scientific studies have shown that most tuna inhabits the sea at a depth of 100-400 meters, juvenile bigeye tuna and yellowfin tuna and skipjack tuna are inhabiting the surface waters of the ocean, generally not more than 50 meters deep, while adult bigeye and yellowfin tuna inhabits the water deeper, and the bigeye tuna's inhabited water is deeper than the yellowfin tuna.
It has a long spawning period and a wide range of spawning areas, making it possible for tuna to spawn throughout the year in various areas of the sea, coupled with a strong reproductive capacity, so that eaters around the world can enjoy its delicious flavor.
Six, habits and characteristics
Tuna body is fusiform, with torpedo body shape, its cross-section is slightly rounded. Strong muscles and crescent-shaped caudal fin, scales have degenerated into small round scales, suitable for fast swimming, generally 30-50 kilometers per hour, the highest speed up to 160 kilometers per hour, faster than the fastest animals on land. Tuna will suffocate if it stops swimming, the reason is that the tuna always open its mouth when swimming, so that the water flow through the gills and oxygen respiration, so in its life it can only non-stop continuous high-speed swimming, even at night also do not rest, just slowed down the swimming speed, reduce the metabolism (this open mouth so that the water flow directly through the gills oxygen respiration respiration is called the impingement respiration, tuna belongs to impingement respiration.) . The color of the tuna's belly is lighter than its back, so that when you look at it from the sea, its light body color is similar to the color of the sea surface; the tuna's travel range can be as far as thousands of kilometers, and it can make inter-oceanic circumnavigation, which is known as "fish without national boundaries". According to scientists, tuna is the only large fish that can swim long distances quickly, experiments show that the tuna can reach 230 kilometers per day.
The tuna's habits are very interesting, it is one of the fastest swimming marine animals, only the most ferocious sharks and large dolphins can match it. At full speed, the tuna can reach speeds of up to 55 nautical miles per hour.
Eight, the body of mystery
1. Amazing food
In order to replenish non-stop swimming and vigorous metabolism consumed energy, the tuna must constantly eat. A pound of tuna a meal to eat the equivalent of 18% of its body weight in food, equivalent to a weight of 150 pounds of men eat a meal with the bones of two large roosters.
2. Swimming speed
Tuna's gill muscles have deteriorated, so it must swim constantly, so that fresh water flow through the gills to obtain oxygen. If the tuna stops swimming, it will die of asphyxiation due to lack of oxygen. When a tuna swims at full speed, its fins contract into the body to minimize drag, and it speeds forward like a loaded cannonball.
3. Warm-blooded
Most fish are cold-blooded, but tuna are warm-blooded, with a body temperature of 93-95 degrees Fahrenheit. The high body temperature and high metabolism make the tuna a superb hunter with its quick and agile reflexes. The tuna has a varied diet, with squid, crabs, eels, shrimp and other such marine animals as its favorites.
4, high-temperature cause
Tuna's temperature is higher than the surrounding water temperature, because of its body on both sides of the skin and muscle vascular network plexus, by the scientists thorough research, tuna's body temperature is higher than that of the surrounding water temperature by 9 ℃. This tireless fast swimmers, muscle contraction force is the main reason to make their body temperature rise. Along the tuna spine on both sides of the powerful muscles and skin on a large number of blood vessel network plexus, indicating that these parts of the metabolism is particularly vigorous, and thus the tuna's flesh resembles beef, is purplish red. It has a high content of hemoglobin and is low in fat but high in strong protein, making it highly nutritious.
Source
Baidu Encyclopedia:/link?url=c5hy_OVgGN6kSkFrYbvqj9KZLupmxmenJ_vSCoDPJS7cWXI3V3R48u5LF81_GgC9rMBGpg9aGKnVS56uI_m3LK