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Butterfly kingfish

Butterfly kingfish

A rare, warm-blooded mackerel of southern oceans.

The butterfly kingfish is a unique member of the mackerel family found in cool southern waters. It stands apart from its relatives due to its large scales and ability to regulate body temperature. This species grows quite large and is occasionally caught by commercial longline fisheries.

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  • Can raise body temperature like a tuna
  • Has enormous pelvic fins as a juvenile
  • Lives in cool waters down to 200 metres
  • Marketed legally as mackerel in the US
  • Only member of its genus and subfamily

What it is

This ray-finned bony fish belongs to the mackerel family but sits in its own distinct genus and subfamily. It features very large cycloid scales covered by a thick fat layer. Juveniles display enormous pelvic fins that tuck into a ventral groove, similar to how other mackerels hide their dorsal spines. The fish lacks a median keel on its tail base, possessing only small lateral keels. It can reach lengths of 1.64 metres and weigh up to 70 kilograms.

Where it lives

The species lives in southern temperate waters around the world. It prefers temperatures between 8 and 15 degrees Celsius, often staying below 10 degrees. These fish inhabit the open ocean at depths reaching 200 metres. While distributed globally in these cool zones, they appear common around Oceania and have been recorded as far north as Hawaii.

How it lives

Unlike most bony fishes, this species is endothermic. It can raise its body temperature above the surrounding water, a trait shared with tunas. A specialised brain heater organ, derived from an eye muscle, helps maintain this warmth. This adaptation distinguishes it from billfishes, which use a different muscle for heating. The fish swims in deep, cool offshore environments.

Fish and people

Regulatory bodies allow this fish to be marketed simply as mackerel. It holds minor importance in commercial fisheries, usually caught incidentally by longlines while targeting other species. Recreational anglers also encounter it, though it remains a rare catch. Its unique status within the mackerel family makes it a subject of taxonomic interest.

Questions people ask about Butterfly kingfish

Is the butterfly kingfish a type of tuna?

It belongs to the same family as tunas but is in its own distinct genus. It shares traits like warm-bloodedness but has a more primitive evolutionary lineage compared to true tunas and mackerels.

How large does this fish grow?

Adults can reach a length of 1.64 metres, which is about 5.4 feet. They typically weigh around 50 kilograms, though specimens up to 70 kilograms have been recorded.

Where can you find butterfly kingfish?

They live in southern temperate waters around the globe. They prefer cool temperatures between 8 and 15 degrees Celsius and are often found in the open ocean at depths up to 200 metres.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Butterfly kingfish", 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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Photo credits on this page

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

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