Siganus rivulatus (Forsskål, 1775)
A pair of S. rivulatus. Photos by MCH/Andreas I. Iliopoulos
Size: maximum length (TL) about 40 cm and a weight round half a kilogram (500 gr), but usually not over 20 cm to 30 cm when adult
Depth: it occurs in shallow waters and found mostly in a depth of about 20 m.
Environment: Reef associated species. The animals form schools (measuring from about 50 to quite many - sometimes – individuals). Usually they stay near the bottom, grazing on algae and sometimes may enter estuaries (thus it is a euryhaline species)
Food: Feeds on algae and phytoplanktonic matter (i.e. small crustaceans and other invertebrates), but it is a mainly herbivorus fish.
Breeding: The animals are reaching maturity when they measure about 15 cm of (TL) length and they breed between June and December. Their eggs hatch one day to thirty six hours (24 h – 36 h) after spawning in temperatures between 24° C – 27° C. Their larvae are found near the water surface and (depending the ambient temperature) start eating in three days after hatching. After about three (3) weeks they metamorphose, form numerous flocks and they migrate in deeper waters, till the weight of about three grammars (3 gr).
Distribution: Southwestern Mediterranean Sea. The species is a Lessepsian migrant. They live in the Red Sea, western Indian Ocean and east Africa. These animals came in the Mediterranean basin through the Suez Canal (after 1869) and they have recorded there sometime on ‘40s for the first time.
The animal on the photo was found on August 2003. Note that just the previous summer these animals were not in these waters, which makes obvious that by time they continue to migrate north.
Common name: Red Sea rabbitfish, marbled spinefoot
General notes: Not a good addition in a marine tank, due to the fact that the animals are schooling and they would need very large tanks. Only when young, one may house a small group of them in a large tank, with rich algal growth.
Many times are found together with cow breams or its relative fishes S. luridus (also a Lessepsian migrant).
Their spines are venomous and hurt a lot.
This species is a Lessepsian migrant