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Slender tuna

Slender tuna

A southern ocean tuna with oily flesh and a slender build.

The slender tuna is the sole member of its genus, inhabiting southern oceans between 20 and 50 degrees south. It reaches one metre in length and feeds mainly on krill, serving as minor bycatch in commercial fisheries.

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  • Only species in the genus Allothunnus
  • Reaches up to 1 metre in length
  • Main diet consists of krill
  • Flesh is high in omega-3 fatty acids
  • Found mainly in southern oceans

What it is

This fish is the only species within the genus Allothunnus. It possesses a more elongated body shape compared to other tunas sharing its range, such as the albacore. The back displays a blue-black hue, while the sides are silvery greyish-white. Some specimens show a coppery sheen immediately after capture. The second dorsal and anal fins are small, resembling those of an albacore, but it lacks the long sweeping pectoral fins typical of that species. The distal portions of its pectoral and pelvic fins are purple, turning black near the bases.

Where it lives

The species inhabits the southern oceans, specifically between latitudes 20 and 50 degrees south. It is primarily found in these open waters. There are two recorded instances of probable vagrants outside this normal range. One was observed in Los Angeles Harbour, and another was found in the North Pacific subarctic gyre. These occurrences are rare exceptions to its usual distribution pattern in the southern hemisphere.

How it lives

It occasionally forms schools while swimming. Its primary food source is krill, which contributes to the oily nature of its flesh. It also preys on squid and smaller fishes, including jack mackerel. The oil content in its body varies throughout its life cycle. Fish that have recently fed contain high levels of oil, whereas specimens caught at the end of their migrations have relatively lower oil concentrations.

Fish and people

This tuna holds minor commercial importance and is mostly taken as bycatch in fisheries targeting other tuna species. The flesh is paler than that of other tunas and has a high oil content. It is considered palatable when cooked and is suitable for canning. The CSIRO once declared it Australia's healthiest seafood dish due to its high concentration of omega-3 polyunsaturated fatty acids.

Questions people ask about Slender tuna

Where does the slender tuna live?

It is found in the southern oceans between latitudes 20 and 50 degrees south. Rare records exist from Los Angeles Harbour and the North Pacific subarctic gyre.

What does the slender tuna eat?

Its main prey is krill. It also consumes squid and smaller fishes such as jack mackerel. This diet contributes to the high oil content in its flesh.

Is the slender tuna good to eat?

Yes, the flesh is palatable when cooked and suitable for canning. It has a high concentration of omega-3 fatty acids, leading some to call it a healthy seafood option.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Slender tuna", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

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The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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