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Understanding for tuna

Author:奥讯

Date:11/23/2013 8:10:22 AM

Hits:1153

I once participated in the East China Sea marine survey ship has just opened near mountain fish , standing on the bow saw about 4 - There are large areas of dark blue color on a partial 500 meters from the sea in a fast moving object ; survey ship via when longitude 125 degrees, has repeatedly seen such a scene . I wondered what this fish is fish , fishing can produce ? The Putuo District fishing happened last real tuna caught by purse-seine , turn our old ideas raised. Aiming at the domestic fishing pressure exists , it is proposed to develop the use of domestic tuna fishery resources of the new fishing project .
According to the East China Sea Fisheries Research Institute of Chinese Academy of Fishery Sciences showed that tuna is widely distributed in the Pacific, Indian and Atlantic low- latitude coastal waters off the coast and oceans . Tuna generic Perciformes Scombridae , also known as tuna, and mackerel , mackerel , mackerel and other relatives , the same scribe Scombridae . Division within and between species has a large variation, classification is also very different , pundits disagree on this issue . Tuna more varieties including 13 species belonging to four genera: tuna genus (Thunnus), tuna genus (Euthynnus), skipjack genus (Katsuwonus) and rudder bonito genus (Auxis). One of the most economic value and market supply large quantity of six species: skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), tuna (Thunnus thynnus), albacore tuna (Thunnus alalunga), Massu tuna (Thunnus maccoyii ) and bigeye tuna (Thunnus obesus). Tuna body elongated , thick and round, was streamlined , tapered tip back and tail base slender, forked caudal fin or crescent . Both sides of the caudal peduncle obvious ridge , back, behind each row of small anal fin . Breastplate shoulders consisting of enlarged scales . Another feature of the subcutaneous vascular network has developed as a long slow swimming thermoregulation means . Giant bluefin tuna (Thunnus thynnus), also known as black tuna, the largest can grow to about 4.3 meters and weighs 800 kilograms . Tuna is generally dark dorsal , ventral white, usually iridescent glitter . So when large tuna swimming in the sea surface , to see is a dark color .
Tuna takes the shape of a spindle with a torpedo shape, slightly rounded in cross-section . Strong muscles and crescent-shaped tail fin , scales to degenerate into small round scales , suitable for fast swimming , the general speed of 30 per hour - 50 km , maximum speed up to 160 kilometers per hour, the fastest than on land animal faster . Therefore, it is more difficult to fishing , mostly in longline Pacific, Indian , Atlantic operations. Of course, there seine fishing .
Bluefin tuna with blue fins and silvery spots or bands, is a precious sport fishing species. Longline is the main practices. Yellowfin tuna is a prized food fish and game fish . Yellowfin tuna in the world live in tropical and subtropical oceans .
The main distribution area : the Indian Ocean , the Pacific , Atlantic tropical and subtropical waters. In China , only distributed in the South China Sea and East China Sea. Many scholars believe that the resource is still possible, because there is no fishing resources is steadily increasing. According to reports, the main yellowfin tuna fishery in the equatorial waters between the latitude of 35 degrees , is the largest yellowfin tuna catches of tuna species.
Yellowfin tuna shape characteristics : a body length of up to three meters and weigh up to 225 kilograms , generally up to two meters large , weighing 100 kg, yellow fin , streamlined body was lean . Juveniles of rapid growth and development of adult fish growth slowed significantly . 3-6 months each year is yellowfin tuna spawning season. A female fecundity between 200-800 million pills of a spawning season females spawn repeatedly , is spawning a batch type . Yellowfin tuna is quite exuberant fecundity .
Therefore , it should be said that the world is now in the yellowfin tuna rational development of the state . Currently the main target of foreign tuna purse seine fishing for skipjack and yellowfin tuna younger because their activities and in clusters near water feeding migratory and other conditions, is more suitable for purse seine fishing , prompting these two types of fish in the catch volume exceeded 100 million tons , respectively , particularly skipjack reached 1,976,400 tons in 1999 , and this is related to the development of the tuna purse-seine fishery .

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