Cutting giant bluefin tuna to luxurious sashimi, teppanyaki tuna / 巨大黑鮪魚切割秀, 鐵板上腹肉 - Taiwanese food
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Pacific bluefin tuna (lat. Thunnus orientalis) is a species of the genus of tuna of the mackerel family. It is the second largest member of its genus after the common tuna, with a maximum recorded length of 3 m and a mass of 450 kg. Pacific bluefin tuna live in subtropical, less often in warm temperate and tropical waters of the Pacific Ocean between 52° N. w. and 50° S. w. and between 112° E. long and 77° west d. These schooling pelagic fish are found both in coastal waters and in the open ocean at depths of up to 550 m. They usually stay in near-surface waters. They make seasonal migrations, moving mainly along the coast. Closely related to common and Australian tuna. The diet consists of small pelagic fish and cephalopods. Reproduction by spawning. Valuable commercial species. Due to overfishing, it has received the conservation status of Near Threatened. Tuna are caught using longlines, purse seines and various hook and line gear. They are a popular sport fishing target. The population is estimated to have declined to 4% of pre-fishing levels in the mid-20th century.
Pacific bluefin tuna are constantly on the move. When they stop, breathing becomes difficult because the gill covers open in accordance with the lateral movements of the body to the left and right. Water passes through the open mouth into the gill cavity only when moving. Tuna are capable of reaching speeds of up to 20-30 kilometers per hour for a short time. In these swimmers (as in mackerel, bonito, swordfish, and marlin), the main locomotor function is performed by the caudal fin, and the short, streamlined body remains almost motionless.
Like other representatives of the genus, Pacific bluefin tuna are capable of maintaining a body temperature elevated relative to the environment due to endothermy. The effect is provided by a complex of subcutaneous blood vessels called lat. Rete mirabile - "wonderful network". This is a dense interweaving of veins and arteries that runs along the sides of the fish’s body and supplies blood to the lateral muscles and the red muscles adjacent to the spine. It allows you to retain heat, warming up cold arterial blood due to venous blood, heated by the work of the muscles. This ensures higher temperatures in the muscles, brain, internal organs and eyes, allowing tuna to swim at high speeds, reduce energy expenditure and allow them to survive in a wider range of environmental conditions than other fish. At moments of greatest energy expenditure, the body temperature of tuna can be 9-10 °C higher than the temperature of the surrounding water.
Tunas are distinguished by a high oxygen capacity of the blood: the hemoglobin content in the blood of these fish reaches 21 g%, while in bonito fish, which are also excellent swimmers, its concentration is no more than 14 g%. Most fish have white flesh, but tuna have muscle tissue that is colored in different shades of red, from pale pink to dark red. This color is given to the myotomal muscles by the oxygen-binding protein myoglobin, which is found in much larger quantities in tuna meat compared to the meat of other fish. Oxygen-rich blood provides muscles with additional energy. Such a system of blood vessels probably increases the elasticity of the body by filling the surface tissues with blood, which allows the fish to make frequent oscillatory movements of the tail. A similar mechanism has been found in cetaceans.
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#streetfood #cook #tuna #omar
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