The lined soapfish has an unusual defence against being eaten: it tastes revolting. When threatened, this small Indo-Pacific fish produces a toxic, soapy slime so bitter that any predator bold enough to swallow it immediately spits it out. Despite its modest size, the lined soapfish is a remarkably effective survivor — a predator in its own right, armed with one of the ocean’s more unusual chemical defences.
Live throughout the Indo-Pacific
They live from the Red Sea and the coast of East Africa all the way to French Polynesia, stretching as far north as Japan and as far south as New Caledonia and Australia. From shallow reef flats and lagoons just 1 metre deep down to seaward reef walls dropping to 130 meters.
The fish that lathers up to avoid being eaten
When agitated soapfish produce a toxic body mucus that forms a bitter, slippery, soapsuds-like froth. This mucus contains a toxic called grammistin, which gives the soapfish its scientific name Grammistes sexlineatus. If a larger grouper tries to eat the soapfish, it immediately spits it out because of its terrible-tasting, poisonous, slimy coating.
Change from spots to stripes
The Lined Soapfish grows to around 27 cm, and changes colour as it grows. The smallest have pale yellow spots with red-edged fins. These spots elongate into three lines as the soapfish mature. When fully grown they have several yellow or creamy colour broken-stripes.
Class: Actinopterygii (Ray-finned fishes) > Order: Perciformes > Family: Serranidae (Groupers and sea basses) > Genus: Grammistidae (Soapfishes)
Sources and References
Lieske and Myers, Coral Reef Guide Red Sea (2012)
Britannica
Diamant, Ariel, and Daniel Golani. “Coloration and Probable Toxicity of Juvenile Soapfish Grammistes Sexlineatus (Pisces: Grammistidae).” Copeia, vol. 1984, no. 4, 1984, pp. 1015-17.
Main photo: Jill Studholme
