The slender tuna, ''Allothunnus fallai'', is a species of

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max len ...

, the only species in the genus ''Allothunnus'', found around the world in the southern oceans between latitudes 20° and 50° South, although there are two records of probable

vagrants Vagrancy is the condition of homelessness without regular employment or income. Vagrants (also known as bums, vagabonds, rogues, tramps or drifters) usually live in poverty and support themselves by begging, scavenging, petty theft, tempora ...

, one in Los Angeles Harbour and the other from the North Pacific subarctic

gyre In oceanography, a gyre () is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction dete ...

. It has a more elongated body than other species of tuna with which it is symaptric such as the

albacore The albacore (''Thunnus alalunga''), known also as the longfin tuna, is a species of tuna of the order Perciformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct s ...

The colour is blue-black on the back with silvery greyish-white sides, however some individuals have a coppery sheen soon after capture. It has a small second

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

and anal fins resembling a small albacore, but the slender tuna lacks the long sweeping pectoral fins characteristic of albacores. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s and pelvic fins are purple on their distal portions and black near their bases. Its length is up to and it can weigh up to . It occasionally forms schools and its main prey is

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are consi ...

but it is also known to prey on squid and smaller fishes, such as jack mackerel. It is a species of minor commercial importance, taken mainly as bycatch by fisheries for other tuna species. It has rather oily flesh, paler than that of other tuna, but the flesh is palatable when cooked, although it is suitable for canning. The high oil content of the flesh is caused by the oily nature of its diet and varies over the tuna's life, fish which have just fed are high in oil but specimens caught at the end of their migrations will have relatively low oild content. The high concentration of omega-3 polyunsaturated fatty acids in the flesh of this species caused the CSIRO to declare that the slender tuna was Australia's healthiest seafood dish.

References

* Tony Ayling & Geoffrey Cox, ''Collins Guide to the Sea Fishes of New Zealand'', (William Collins Publishers Ltd, Auckland, New Zealand 1982)

External links

* * {{Taxonbar, from=Q18960418 Scombridae Fish described in 1948 Tuna