Southern bluefin tuna

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Southern bluefin tuna
Drawing of a southern bluefin tuna.

Drawing of a southern bluefin tuna.

Systematics
Spinefish (Acanthopterygii)
Perch relatives (Percomorphaceae)
Order : Scombriformes
Family : Mackerel and tuna (Scombridae)
Genre : Tuna ( Thunnus )
Type : Southern bluefin tuna
Scientific name
Thunnus maccoyii
( Castelnau , 1872)

The southern bluefin tuna ( Thunnus maccoyii ) is a tuna from the Scombridae family . The species is an endangered food fish.

etymology

The additional species maccoyii refers to Frederick McCoy . He was the first director of the National Museum of Victoria in Australia.

features

The southern bluefin tuna is whitish on the underside and belly and has a lateral iridescent blue band. The first dorsal fin is deep yellow, while the second and anal fin are light yellow in color. The finlets are colored yellow with black tips. The skeleton has 18 pre-caudal and 21 caudal vertebrae. The fins formula is: D XII – XIV / 13–16 + 8–10, A 12–15 + 7–10, pectoral 33–36, C 17, PI / 5. Life expectancy is around 12 years, with isolated cases of older specimens being known. The species reaches a height of 160–200 cm, the record is 225 cm. The weight for a 180 cm fish is about 100-130 kg.

Way of life

The species occurs in the southern areas of the western Atlantic , Indian Ocean and Tasman Sea along the 30th to 50th parallel  - in exceptional cases up to 60 ° S - in the epipelagic . The species prefers cool water temperatures of 5–20 ° C for most of its lifetime, although spawning fish and larvae are observed in waters with surface temperatures of 20–30 ° C. The adults usually migrate to spawn in warmer waters between Australia and Indonesia up to 10 ° S. The spawning season takes place during the summer in the southern hemisphere from September to March. After the larval stage, the juveniles migrate to the Great Australian Bight (GAB). A cycle can be observed up to the age of five: During the summer the animals stay in the GAB, while they migrate to New Zealand or South Africa for the winter . Animals older than five years rarely return to the GAB and are distributed across the aforementioned oceans. The southern bluefin tuna feeds on a variety of different fish species, molluscs and crustaceans .

Economical meaning

In Australia in particular, catching the species is of economic interest. The fishing areas extend along 10 ° to 170 ° W along the southern hemisphere, although a concentration around Tasmania , New Zealand and South Africa can be observed. Fishing is usually done with longlines , while in Australia purse seine fisheries are used to transfer the fish to aquaculture .

At auctions in Tokyo, some of the copies fetch high-priced bids of over US $ 10,000  . Kiyoshi Kimura, head of a Japanese restaurant chain, bought a copy for $ 3.1 million in 2019. The price depends largely on the fat content and the quality of the meat. This is usually sold in sashimi markets in Tokyo . It is estimated that the southern bluefin tuna fishery is worth over 1 billion euros .

threat

The species is listed as "Critically Endangered" on the Red List of Threatened Species . The reasons for this are slow growth with late sexual maturity , pronounced cyclical migration and the fact that there is only a single spawning site. The main cause, however, is seen to be the intensive fishing of the stocks since the early 1950s. Stocks are believed to have decreased by 85% from 1973-2009 with no signs of recovery.

Individual evidence

  1. ^ A b c Dianne J. Bray, Martin F. Gomon: Southern Bluefin Tuna, Thunnus maccoyii (Castelnau 1872). In: Fish of Australia. Accessed November 26, 2018 .
  2. ↑ a b c d Scombrids of the world . An annotated and illustrated catalog of tunas, mackerels, bonitos and related species known to date. tape 2 . Rome 1983, ISBN 92-5101381-0 , pp. 87-88 ( fao.org [PDF; 6.0 MB ; accessed on November 27, 2018]).
  3. ↑ a b Takasho Kitagawa, Shingo Kimura (Ed.): Biology and Ecology of Bluefin Tuna . CRC Press, 2015, ISBN 978-1-4987-2488-3 , chap. 8 , p. 189–195 ( limited preview in Google Book Search [accessed November 27, 2018]).
  4. ↑ a b B. Collette et al. : Thunnus maccoyii, Southern Bluefin Tuna . In: Red List of Endangered Species . 2011 ( iucnredlist.org [accessed November 27, 2018]).
  5. ↑ Japan's 'tuna king' shells out $ 3.1 million for bluefin at Tokyo's new fish market. thenational.ae, January 5, 2019, accessed April 17, 2020 .