Cobia , or nigrite , or sergeant fish , or canadus [1] ( lat. Rachycentron canadum ) is a species of ray-finned fish from the order Carangiformes , the only representative of the cobium genus [1] , or nigrite [1] ( Rachycentron ) and the kobian family [1] ] (Rachycentridae) [2] .
| Cobia |
Male | 
Female |
|
| Scientific classification |
|---|
| No rank : | Bilateral symmetrical |
| Family: | Cobium ( Rachycentridae Gill , 1896 ) |
| Gender: | Cobia ( Rachycentron Kaup, 1826 ) |
|
| International scientific name |
|---|
Rachycentron canadum ( Linnaeus , 1766 ) |
|
The fish has a smooth, elongated, torpedo-shaped body and a flat, wide head. The length of the fish is up to 1.80 m, weight - 70 kg. The body is dark brown with white patches on the belly. The dorsal fin is represented by 7β11 short, strong spines, not connected by the membrane. The anal fin is long and has from 2 to 3 hard and from 22 to 28 soft rays.
Kobia lives in coastal, pelagic waters of all tropical and subtropical seas. This predatory fish preys on other fish, as well as crabs and squids.
Content
It reaches a maximum length of 2 meters and a maximum weight of 68 kg [3] . The body is elongated spindle-shaped (torpedo-shaped), the head is flat and wide. The eyes are small, the lower jaw protrudes slightly beyond the upper jaw. On the jaws, tongue and palate, two rows of teeth in the form of villi. The smooth body is covered with small scales, the dark brown coloring of the back gradually changes on the sides to light gray tones, the belly is silver-white. Two longitudinal stripes are distinguishable along the sides. The bands may not be pronounced with the exception of the spawning period, when the color of the fish becomes brighter and the fish take a pronounced striped look.
Large pectoral fins are usually horizontal, therefore, underwater observations of these fish can be confused with small sharks. When catching fish from the water, horizontally located pectoral fins allow cobia to remain upright, and vigorous resistance makes them dangerous.
The first dorsal fin consists of 6β9 short, strong, and sharp spines not connected by a membrane. The second soft dorsal fin with 31 rays is a long, crescent-shaped. Anal fin of the same shape and length with 2-3 spiny rays and 24 articulated (soft) rays. The caudal fin in mature individuals is forked in the shape of a crescent, dark brown. The upper lobe is longer than the lower. The name of the family Rachycentridae comes from the Greek rhachis - spine - and kentron - sting, which is probably due to the characteristic appearance of the dorsal fin. The swim bladder is absent.
The family of cobium (or nigrite), which is undoubtedly close to the horse mackerel , and to a certain extent also to the sticking fish, includes only one species. It is similar to closely related remora from the family of adherent (Echeneidae). However, cobia lacks a suction cup, the body is more complete and the fins are more developed and more forked, rather than rounded. Juveniles with noticeable stripes of black and white. In juveniles, the caudal fin is more rounded, and not forked, as in adult fish.
Cobia is a large pelagic fish, usually lead a solitary life with the exception of annual spawning aggregations, however, large groups of fish are often observed at reefs, wrecks of shipwrecks, pile structures, buoys and other obstacles. Mangroves also enter the estuary in pursuit of prey. Distributed in the coastal waters of all subtropical and tropical seas of the eastern and western Atlantic , in the Caribbean , in the Indo-Pacific from India to Australia and Japan [3] [4] . None in the Eastern Pacific. The largest specimen, caught by spinning off the coast of Australia, weighed 60 kg. Eurythermic fish withstand a wide range of temperatures from 1.6 to 32.2 Β° C. Euryhaline fish resistant to changes in salinity from 5 to 44.5 β° [5] .
It feeds mainly on crabs , squid and pelagic fish. In particular, Dasyatis marianae stingers can become their prey [6] . Often cobies follow large animals such as sharks , turtles and stingrays , hoping for leftovers. Kobia is a very curious fish, does not feel fear from boats and sometimes pursues fish caught by fishermen right up to the side of the boat. Attacks of other fish on adult cobia have not been documented, however, the observations of fishermen indicate the feeding of mako sharks by adult cobia during their spring migrations in the Gulf of Mexico. It is known that the adult coryphaena ( Coryphaena hippurus ) is often fed by cobia juveniles.
Cobias form large spawning clusters in the pelagic coastal waters. Females sweep a large number of small (up to 1.2 mm in diameter) caviar. Fertilized caviar is moved by currents in the water column. Larvae also lead a pelagic lifestyle, almost defenseless during the first week until the development of the eyes and mouth. Cobias are fast-growing fish. Males first mature at the age of 2 years, and females at the age of 3 years. Life expectancy of individuals of both sexes is up to 15 years. Spawning occurs during daylight hours in April-September. Spawning is portioned; females can spawn up to 30 times per season with an interval of 1-2 weeks [7] . Cobia is often infected with parasites, such as nematodes, trematodes, cestodes, copepods, and scratches.
Kobia makes seasonal migrations along the coast in search of waters with a preferred temperature. After wintering in the Gulf of Mexico, they migrate north, crossing the coastal waters of Florida in March and reaching the coast of Maryland in summer.
Valuable expensive fish with dense and delicious meat. However, it does not have an independent commercial value, since it leads a solitary lifestyle and does not form commercial clusters. Of great interest to sports fishermen. In the official list of fish records caught on sea spinning, cob weighing 46.4 kg is listed. It is an object of aquaculture. Cobia meat is usually sold fresh. It is cooked on the grill or in the form of a boiled filet.
Cobia is considered one of the most attractive candidates in the world for warm-water mariculture in open waters [8] [9] . The high growth rate when kept in cages, as well as the exceptional quality of meat, make these fish one of the most important objects of mariculture of the future [9] .
Cobies are currently grown in coastal pools, ponds or coastal cages, and then in open sea cages in many regions of Asia and along the coast of the United States, Mexico and Panama. In Taiwan, cobalt juveniles weighing 100β600 g are transferred to marine cages and are grown to 6β8 kg in 1β1.5 years, which is an acceptable size for export to Japan [9] . Now about 80% of marine cages in Taiwan are allocated for cobia mariculture. In 2004, according to the FAO, 80.6% of world cobal production was accounted for by China and Taiwan. The third world producer is Vietnam, where 1,500 tons of cobium were grown in 2008 [10] . The success of cobia mariculture in Taiwan and the development of growing technologies have allowed the reproduction of this fish in submersible cages in Puerto Rico and the Bahamas [11] .
Large depths under sea cages, strong currents and a significant distance from the coast reduce the potential negative impact of mariculture on the environment. The use of marine cages in open waters may be the most environmentally acceptable method for commercial mariculture of fish [12] . However, some problems in the cultivation of cobia still exist, and to increase production, these problems must be resolved. Among the main problems are the high mortality due to stress during transportation to marine cages, as well as fish diseases both during initial rearing and at sea.
- β 1 2 3 4 Reshetnikov Yu.S. , Kotlyar A.N. , Russ T.S. , Shatunovsky M.I. Pyatilingual dictionary of animal names. Fish. Latin, Russian, English, German, French. / edited by Acad. V. E. Sokolova . - M .: Rus. Yaz., 1989 .-- S. 254. - 12,500 copies. - ISBN 5-200-00237-0 .
- β Nelson J. S. , Grande T. C., Wilson M. V. H. Fishes of the World . - 5th ed. - Hoboken: John Wiley & Sons , 2016 .-- P. 384. - 752 p. - ISBN 978-1-118-34233-6 . - DOI : 10.1002 / 9781119174844 .
- β 1 2 Kobia in the FishBase database.
- β Ditty JG, Shaw RF Larval development, disribution, and ecology of cobia Rachycentron canadum (Family: Rachycentridae) in the northern Gulf of Mexico (Eng.) // Fishery Bulletin. - 1992. - Vol. 90, no. 4 . - P. 668-677.
- β Resley MJ, Webb KA, Holt GJ Growth and survival of juvenile cobia Rachycentron canadum cultured at different salinities in recirculating aquaculture systems (Eng.) // Aquaculture. - 2006. - Vol. 253, no. 1-4 . - P. 398-407.
- β Gomes UL, Rosa RS and Gadig OBF Dasyatis macrophthalma sp. n .: A New Species of Stingray (Chondrichthyes: Dasyatidae) from the Southwestern Atlantic (Eng.) // Copeia. - 2000. - Vol. 2000, no. 2 . - P. 510-515. - DOI : 10.1643 / 0045-8511 (2000) 000 [0510: DMSNAN] 2.0.CO; 2 .
- β Brown-Peterson NJ, Overstreet RM, Lotz JM Reproductive biology of cobia, Rachycentron canadum, from coastal waters of the southern United States. Fishery Bulletin. - 2001. - Vol. 99., no 1. - P. 15-28.
- β Kaiser JB, Holt GJ Cobia: a new species for aquaculture in the US // World Aquaculture Magazine. - 2004. - Vol. 35, no 2. - P. 12-14.
- β 1 2 3 Liao IC, Huang TS, Tsai WS, Hsueh CM, Chang SL, Leano EM Cobia culture in Taiwan: current status and problems // Aquaculture. - 2004. - Vol. 23, no 1-4. - P. 155-165.
- β Nhu VC, Nguyen HQ, Le TL, Tran MT, Sorgeloos P., Dierckens K., Reinertsen H., Kjorsvik E., Svennevig N. Cobia Rachycentron canadum aquaculture in Vietnam: recent developments and prospects // Aquaculture. - 2011 .-- Vol. 315, no 1-2. - P. 20-25.
- β Benetti DD, Orhun MR, Zink I., Cavalin FG, Sardenberg B., Palmer K., Denlinger B., Bacoat D.,. O'Hanlon B. 2007. Aquaculture of cobia (Rachycentron canadum) in the Americas and the Caribbean. Pages 57β78. In: I C. Liao and EM Leao (editors) In: Cobia Aquaculture: Research, Development and Commercial Production. Asian Fisheries Society, Manila, Philippines, World Aquaculture Society, Louisiana, USA, The Fisheries Society of Taiwan, Keelung Taiwan, and National Taiwan Ocean University, Keelung, Taiwan.
- β Benetti DD, AlarcΓ³n JF, Stevens OM, O'Hanlon B., Rivera JA, Banner-Stevens G., Rotman FJ 2003. Advances in hatchery and grow out technology of marine fish candidate species for offshore aquaculture in the Caribbean. 54th Ann. Gulf and Caribbean Fisheries Institute, Nov. 2001, Turks and Caicos. 54 : 473β487.
- Joseph S. Nelson : Fishes of the World , John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
