How to identify atlantic bonito

Sarda sarda · Scombridae

The characters that identify atlantic bonito, ranked by how far each one can be trusted on its own.

Safety

Species that bite — Can cause injury needing treatment

Conical teeth in a fast fish that thrashes at the point of landing, frequently on rock or a quay.

What reduces it: Keep fingers clear of the mouth, use pliers or a de-hooking tool, and control the fish before touching it.

Cliffs and rock platforms — Can cause serious injury or death

A great deal of the shore fishery for this species is from ocean rock marks and breakwaters, where swell sweeps anglers off.

What reduces it: Never fish rock marks alone. Watch a mark for a full set cycle before committing. Wear a buoyancy aid and footwear with grip, and plan the escape route first.

An Atlantic bonito held horizontally above the sea, showing several dark stripes running obliquely down and forward across the green-blue back and onto the upper flank, a pointed head, and conspicuous teeth in the open jaw. — Atlantic bonito (Sarda sarda). The dark stripes slant OBLIQUELY across the back and onto the upper flank — the character that separates it from the wavy-barred mackerels and from little tunny, whose markings stay above the lateral line.Identified by: The diagnostic is unusually clean. Dark stripes run OBLIQUELY — angled down and forward — across the back and onto the upper flank, which is the character of Sarda and is visible along the whole fish. That separates it from Atlantic mackerel, whose bars are near-vertical and wavy; from little tunny, whose markings stay above the lateral line; and from skipjack, whose stripes run along the belly. The conical teeth are supporting and are inconsistent with Thunnus.ricofish — CC0, via Wikimedia Commons — source, licence

Look at this first

Look at the back and ask which way the stripes run. On an Atlantic bonito several dark lines slant OBLIQUELY — down and forward — across the back and onto the upper flank. Mackerel bars run near-vertically and wave; skipjack stripes run along the belly. Then open the mouth: bonito have real teeth.

Diagnostic — settles it on its own

Each of these settles the identification on its own. If one is clear, you have your answer.

Oblique dark stripes across the back
Several dark stripes run diagonally down and forward across the dorsal surface, continuing onto the upper flank. This is the character of Sarda and it is the one to lead with, because it is a pattern geometry rather than a colour and it survives on a dead fish for as long as the markings last.
Conspicuous conical teeth
The jaws carry a row of well-developed pointed teeth, obvious in an open mouth. Tunas of similar size have far smaller teeth, and mackerel have fine ones. Together with the stripe angle this settles the fish against everything it is likely to be confused with.

Supporting — use with other characters

Real characters that are not conclusive by themselves. Use two or three together.

No markings and no spots below the lateral line
The belly and lower flank are plain silver. Little tunny carries dark spots below the pectoral fin and its wavy markings stay above the lateral line, which is the reciprocal check to the stripes running onto the flank here.

Suggestive only — varies with condition

Hints only. These vary with condition, season, water and how long the fish has been out of it, and a fish that contradicts them is still the same species.

The green-blue back
Vivid in a live fish and gone within an hour of death, when the whole animal goes leaden grey. Never identify a scombrid on the colour of its back, and be particularly careful with photographs taken on a deck in the sun.

What it gets confused with

Little tunny and other Euthynnus, separated by whether the markings cross the lateral line and by the spots below the pectoral.
Skipjack tuna, whose stripes run horizontally along the belly rather than obliquely across the back.
Atlantic mackerel at small sizes, separated by the near-vertical wavy bars and the absence of real teeth.
Other Sarda species outside the Atlantic, which this page does not attempt to separate.

Side by side: Atlantic bonito vs Narrow-barred Spanish mackerel.

Where this stops working

The stripe geometry is reliable while the markings are visible and they fade as a fish deteriorates, so a bonito that has been dead and warm for some hours can lose the character the page depends on. Small fish are harder, because the stripes are less developed and the teeth are less obvious. Where the fish is going to be eaten, the identification matters for a reason beyond naming: scombrid flesh forms histamine rapidly and the handling that prevents it is the same whichever scombrid this is, so an uncertain identification is not a reason to delay bleeding and chilling.

The full record

This page covers identification only. The Atlantic bonito record covers behaviour, lifecycle, distribution, handling and the sources behind all of it.

Reviewed 2026-08-13.

More about this fish

Telling it apart is one question. Here are the others.

Similar and related fish

What these connections rest on (3)

Scientific evidence — 3 connections

Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.

European anchovy
Recorded diet evidence identifies Engraulis encrasicolus as a food item of this predator at species level. The edge is written at that granularity and no further.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: Food items recorded for this predator, including Engraulis encrasicolus.States this directlyPassage read and verified
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Species account describing the diet of this predator in the region where Engraulis encrasicolus occurs.Background and mechanism onlyCitation checked — the work exists and is described correctly
European sprat
Recorded diet evidence identifies Sprattus sprattus as a food item of this predator at species level. The edge is written at that granularity and no further.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: Food items recorded for this predator, including Sprattus sprattus.States this directlyPassage read and verified
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Species account describing the diet of this predator in the region where Sprattus sprattus occurs.Background and mechanism onlyCitation checked — the work exists and is described correctly
Narrow-barred Spanish mackerel
A taxonomic and identification comparison naming both binomials.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: That Scomberomorus commerson and Sarda sarda are both Scombridae possessing well-developed teeth, unlike the true tunas of Thunnus.States this directlyPassage read and verified

Where you will find it

2 more

The Strait of Messina Fishing regions
The West African coast Fishing regions

What these connections rest on (10)

Scientific evidence — 10 connections