| ||Thunnus phillipsi Jordan & Evermann, 1926|
| ||Thunnus thynnus maccoyii Serventy, 1956|
|En - Southern bluefin tuna, Fr - Thon rouge du Sud, Sp - Atún rojo del Sur.|
3Alpha Code: SBF Taxonomic Code: 1750102608|
|Scientific Name with Original Description|
|Thunnus maccoyii Castelnau, 1872, Proc.Zool.Acclim.Soc.Victoria, 1:104-105 (Melbourne, Australia).|
|A very large species, deepest near middle of first dorsal fin base.
Gillrakers 31 to 40 on first arch.
Pectoral fins very short, less than 80% of head length (or between 20.2 and 23% of fork length), never reaching the interspace between the dorsal fins.
Ventral surface of liver striated. Swimbladder present.
Vertebrae 18 precaudal plus 21 caudal.
Colour: lower sides and belly silvery white with colourless transverse lines alternated with rows of colourless dots (the latter dominate in older fish), visible only in fresh specimens; first dorsal fin yellow or bluish; anal fin and finlets dusky yellow edged with black; median caudal keel yellow in adults.
|Probably found throughout the Southern Ocean south of 30° S.|
|Habitat and Biology|
|Epipelagic, oceanicin cold temperate waters, confined to temperatures between 5 and 20 C for much of its life span; spawning fish and larvae, however, are encountered in waters with surface temperatures between 20° and 30° C. In adults, seasonal migrations are observed between the warm water western and northwestern Australian spawning grounds (maximum catches are recorded at temperatures between 23° and 26° C) and coldwater feeding grounds off Tasmania and New Zealand (at temperatures of 13° to 15° C).
The spawning season extends throughout the southern summer from about September/October to March. Fecundity of a 158 cm long female with gonads weighing about 1.7 kg each was estimated at about 14 to 15 million eggs.
The food spectrum, covering a wide variety of fishes (cold and warm water species from different depth strata), crustaceans, molluscs, salps and other groups, reveals the southern bluefin tuna as an opportunist.It is in turn preyed upon by sharks, dolphins, seals and billfishes. Longevity is believed to be at least 12 years, older specimens being rarely encountered. One 3-year old individual was tagged off Albany, Australia, and recaptured off South Australia after 15 years and 4 months, suggesting that this species may attain an age of 20 years.
|Maximum fork length is 225 cm (Yukinawa, 1970). In the Indian Ocean, common sizes range between 160 to 200 cm fork length (Silas s Pillai, 1982). The all-tackle angling record is a 158 kg fish with a fork length of 203 cm taken off Whakatane, New Zealand in 1981. Length-weight correlations vary, particularly in adult fish in relation to physiological condition. A 180 cm long southern bluefin tuna may have a gutted weight of roughly 102 to 134 kg. Length at first maturity is estimated by circumstancial evidence at 130 cm, equivalent to about 40 kg of weight.|
|Interest to Fisheries|
|Southern bluefin tuna is an important commercial species, especially off Australia. Between 1975 and 1981 the world catch varied between a maximum of 43 223 metric tons (in 1976) and a minimum of 32 415 metric tons (in 1978). Japan and Australia landed the bulk of the catches (34 755 out of a total of 34 970 metric tons in 1981) (FAO, 1983). The major surface fishing grounds are found off New South Wales (peak catches in November and December) and in South Australian coastal waters (peak season February through April). Initially, in the fifties and early sixties, trolling was the dominant fishing technique but it was subsequently replaced by live-bait-and-pole fishing. Recently a specialized fishery for sashimi-quality has been developed by New Zealand fishermen. The main longline fishing grounds extend from 10° to 170° W with concentrations off Tasmania, New Zealand and South Africa. They shift seasonally associated with changes in hydrographical conditions. With the introduction of monthly sea surface temperature charts as an aid in fish locating, fishing operations increased their efficiency. On the Tasmanian and New Zealand grounds the fishing season peaks from June through September, and off Cape Town, from May to August, as expressed by maximum hook rates. Adult fish (over 130 cm fork length) are predominantly caught off New Zealand, Tasmania and on the Western Australian (spawning) longline fishing grounds.|
This species is prized for the sashimi markets of Japan, and individual fish have brought more than US$ 10 000 on the auction in Tokyo. Market prices change dramatically with the fat contents i.e. quality of the meat. Fat prespawning southern bluefin tuna fetch high prices while spent individuals meet low appreciation.A management scheme for the conservation of the stock is in operation. It involves an increase in the age at first capture through a voluntary scheme of closed seasons in areas where juveniles and up to 5-year-old fish aggregate; likewise, the Australian government has imposed restrictions on the number of boats allowed to operate within its waters. The total catch reported for this species to FAO for 1999 was 17 186 t. The countries with the largest catches were Japan (7 314 t) and Australia (5 583 t).
|former USSR :
Avstraliijskaya tunets .|
Southern bluefin tuna ,
Southern tunny .|
Bach maguro ,
Indo (Goshu) maguro ,
Minami maguro .|
|NEW ZEALAND :
Bluefin tuna ,
|SOUTH AFRICA :
Southern bluefin tuna ,
Suidelike blouvin-tuna .|
Fischer's Whitehead, eds (1974, Species Identification Sheets Eastern Indian Ocean/Western Central Pacific)
Olson, (1980, summarizes i.e. growth parameter estimates)
Shingu, (1963)(1981, reports i.e. population parameters)