An olive-silver fish to 30 cm (12 in) with fine gold lines along the flank, in schools that arrive on a patch of algae, crop it and leave together. It is one of the most numerous grazers in shallow water here and it is treated as food across the region.
Every fin spine is venomous. Thirteen dorsal, seven anal and two pelvic spines carry venom glands, which is why the family is called spinefoot and why fishermen handle them with a rag; the sting is intensely painful and swells hard, and hot water is the standard first aid. Nothing about the fish is aggressive - the spines are strictly for whatever tries to eat or grab it.
Schooling has a purpose beyond safety. A wall of grazers can overwhelm the defense of a damselfish that farms an algae patch, which one or two fish could never enter, so the school is a way of taxing the reef's farmers.
It was also one of the first fish through the Suez Canal (🇪🇬 Egypt), reaching the Mediterranean by 1927, and it is now abundant there - one of the small number of Lessepsian migrants that became a commercial fishery in its new sea rather than a nuisance.
The species. Siganus rivulatus Forsskål & Niebuhr 1775 - rivulated. ETYFish
- olive-silver body with fine wavy gold lines along the flank
- small mouth with a slightly protruding snout, made for cropping algae
- moves in schools that graze the same patch and then move on together
- length up to 30 cm
