Longtail Tuna

This species is known to be fished off Japan (but is very rare), the Philippines, Australia, Papua New Guinea, Indonesia, and India, but catch statistics were only reported for Australia and Papua New Guinea, ranging between only 9 and 59 t per year in the period from 1975 to 1980. In 1981, catches of 350 t were for the first time reported by the United Arab Emirates bringing the total to 368 t in this year (FAO, 1983). This is doubtlessly a still gross underestimate of the actual landings of this species. Fishing gear comprise trolls, driftnets, and longlines. The total catch reported for this species to FAO for 1999 was 103 851 t. The countries with the largest catches were Thailand (46 361 t) and Iran (Islamic Rep. of) (23 465 t).

A small species, deepest near middle of first dorsal fin base. Gillrakers few, 19 to 27 on first arch. Second dorsal fin higher than first dorsal; pectoral fins short to moderately long, 22 to 31% of fork length in smaller specimens (under 60 cm fork length) and 16 to 22% in larger individuals; ventral surface of liver not striated. Swimbladder absent or rudimentary. Vertebrae 18 precaudal plus 21 caudal. Colour: lower sides and belly silvery white with colourless elongate oval spots arranged in horizontally oriented rows; dorsal, pectoral and pelvic fins blackish, tip of second dorsal and anal fins washed with yellow; anal fin silvery; dorsal and anal liver finlets yellow with greyish margins; caudal fin blackish, with streaks of yellowish green.

Indo-West Pacific Ocean from Japan south through the Philippines to Papua New Guinea, New Britain, the northern three quarters of Australia (Twofold Bay, New South Wales to Freemantle, Western Australia) west through the East Indies to both coasts of India, southern Arabian Peninsula, the Red Sea and the Somalia coast.

Maximum fork length is about 130 cm. In the Indian Ocean, common fork lengths range between 40 and 70 cm (Silas & Pillai, 1982). The all-tackle angling record is a 35.9 kg fish of 136 cm fork length taken at Montagne Island, New South Wales, Australia, in 1982.

An epipelagic, predominantly neriticspecies avoiding very turbid waters and areas with reduced salinity such as estuaries. Longtail tuna may form schools of varying size.Being an opportunistic feeder, its diet includes many species of crustaceans, cephalopods and fishes, at varying percentages.

A small species, deepest near the middle of the first dorsal fin base. The second dorsal fin is higher than the first dorsal fin; the pectoral fins are short to moderately long; swim bladder is absent or rudimentary. Lower sides and belly silvery white with colorless elongate oval spots arranged in horizontally oriented rows. The dorsal, pectoral and pelvic fins are blackish; the tip of the second dorsal and anal fins are washed with yellow; the anal fin is silvery; the dorsal and anal finlets are yellow with grayish margins; the caudal fin is blackish, with streaks of yellow green.

Vertebrae: 39

Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.

Didymocystoides Infection 1. Parasitic infestations (protozoa, worms, etc.)

Didymocystis Infestation 12. Parasitic infestations (protozoa, worms, etc.)

Didymocystis Infestation 10. Parasitic infestations (protozoa, worms, etc.)

Didymocystis Infestation 2. Parasitic infestations (protozoa, worms, etc.)

Terranova Disease. Parasitic infestations (protozoa, worms, etc.)

Scolex Infestation (Scolex pleuronectis). Parasitic infestations (protozoa, worms, etc.)

Pseudocycnus Disease. Parasitic infestations (protozoa, worms, etc.)

Didymocystis Infestation 21. Parasitic infestations (protozoa, worms, etc.)

Didymocystis Infestation 19. Parasitic infestations (protozoa, worms, etc.)

Metapseudaxine Infestation. Parasitic infestations (protozoa, worms, etc.)

Caballerocotyla Disease. Parasitic infestations (protozoa, worms, etc.)

Caballerocotyla Infestation 5. Parasitic infestations (protozoa, worms, etc.)

Predominantly neritic species avoiding very turbid waters and areas with reduced salinity such as estuaries. May form schools of varying size. Feeds on a variety of fishes, cephalopods, and crustaceans, particularly stomatopod larvae and prawns (Ref. 9684). Marketed mainly fresh and dried salted (Ref. 9684), but also smoked, canned and frozen (Ref. 9987).

fisheries: highly commercial; gamefish: yes; price category: very high; price reliability: reliable: based on ex-vessel price for this species

主要分布於印度-西太平洋，由日本南至巴布新幾內亞及澳洲，沿印度、阿拉伯半島南部、紅海至索馬利亞的沿岸。台灣各地均產，尤以東部及南部產量最多。

沿岸重要之漁獲物，全世界年產量在100,000-500,000公噸。一般漁法包括延繩釣、圍網及流刺網等。可作生魚片或加工以及各種烹煮調理皆宜。

體紡錘形，橫切面近圓形，稍側扁；尾柄細長，平扁，每側具發達的中央隆起脊，尾鰭基部每側另具小隆起脊2條。眼中大。上下頜各具細小尖齒一列。鰓耙正常，第一鰓弓上之鰓耙數為19-27。體被細小圓鱗，頭部無鱗，胸部鱗片特大，形成胸甲。第一背鰭具硬棘XIII-XIV，與第二背鰭起點距離相當近，其後具8-9個離鰭；臀鰭與第二背鰭同形，不特別延長而略呈鐮刀形，較胸鰭為短；胸鰭略短於頭長，僅延伸至第二背鰭起點下方；尾鰭新月形。體背側藍黑色，腹部銀白色，體側具有5-10條銀白色點狀縱帶。背鰭、胸鰭及腹鰭灰黑色；離鰭均為黃色而帶灰緣；尾鰭灰黑而帶黃綠色光澤。

沿岸表層洄游魚類，具有避開混濁水域及低鹽度水域之習性。以洄游性之小型魚類，如鯖等為食，亦捕食甲殼類及頭足類等。

Thunnus tonggol is a species of tuna of tropical Indo-West Pacific waters.

It is commonly known as the longtail tuna or northern bluefin tuna. The usage of the latter name, mainly in Australia to distinguish it from the southern bluefin tuna, leads to easy confusion with Thunnus thynnus of the Atlantic and Thunnus orientalis of the North Pacific. Compared to these "true" bluefins, Thunnus tonggol is more slender and has shorter pectoral fins.

Thunnus tonggol reaches 145 centimetres (57 in) in length and 35.9 kilograms (79 lb) in weight. Compared to similar-sized tunas, its growth is slower and it lives longer, which may make it vulnerable to overfishing.

Predominantly neritic species avoiding very turbid waters and areas with reduced salinity such as estuaries. May form schools of varying size. Feeds on a variety of fishes, cephalopods, and crustaceans, particularly stomatopod larvae and prawns (Ref. 9684). Marketed mainly fresh and dried salted (Ref. 9684), but also smoked, canned and frozen (Ref. 9987).