THE ANIMAL FILES

Flathead grey mullet

Mugil cephalus

A fish can use river water and still return to sea to spawn.

Flathead grey mullet live in fresh, brackish and marine water. Fish growing in rivers and estuaries return to the sea to spawn, linking these habitats across the life cycle. Silver flanks and lengthwise stripes mark their bodies.[1]

Follow the evidence ↓
Flathead grey mullet
Image: Roberto Pillon · Commons · CC BY 3.0
A silver-sided body
Sides are silver beneath an olive back.[1]
Moving across salinities
The species tolerates a broad salinity range.[1]
A marine spawning connection
Spawning migrations lead back to sea.[1]

A silver-sided body

The back is olive green, the sides silvery and the belly pale. Several horizontal stripes can run along the body, and the lips are thin.[1]

Moving across salinities

Records include estuaries, lagoons, coastal sea and lower rivers. Individuals can live in fresh water as well as brackish and marine habitats. A freshwater capture therefore does not by itself establish a separate freshwater-only species.[1]

A marine spawning connection

Fish living in rivers and estuaries migrate back to the sea to spawn. A river-to-sea route therefore connects feeding habitat with a reproductive habitat; occupying fresh water does not mean the whole life cycle takes place there.[1]

A COMMON MIX-UP

Does finding a mullet in a river prove it never uses the sea?

No. This species uses several salinities and returns to sea for spawning.[1]

TRY A LITTLE REASONING

Why could a blocked river-to-sea route matter beyond one local pool?

Reveal the explanation

It can separate habitats used during different parts of the life cycle, including the route to marine spawning.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Flathead grey mullet (cited revision)
  2. NCBI Taxonomy — Mugil cephalus

Last fact check:

One discovery leads to another

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