Sargassum fish are present; the gills open as pores near the base of the pectoral fins. The anal fin has no spines and seven to 13 soft rays. The pelvic fins are large and the pectoral fins have 9-11 rays and are stalked and able to grip objects. The outer rays of the tail fin are simple, but the central rays are forked. The sargassum fish has a cosmopolitan distribution in tropical and subtropical seas down to a depth around . It is found in parts of the Atlantic Ocean and the Indo-Pacific Ocean, where drifting seaweed accumulates. In the western Atlantic,
Sargassum muticum observed in temperate environments. "Sargassum muticum" grows from half-tide to infralittoral areas (to a depth of 10 m.). It is fixed on solid substrates like rocks, stones, shells. It is highly tolerant towards temperature and salinity variations. The optimal temperature is between 17 and 20 °C but it tolerates -9 and 30 °C. Originally from Japan, it is thought to have gained worldwide distribution through being transported with Japanese oysters ("Crassostrea gigas"). "Sargassum muticum" was introduced to the Californian coast in the 40's and in Europe in the 70's (The species was first found in the British Isles in the