The Sargassum Fish (Histrio histrio), also known as the Sargassum Anglerfish or Frog Fish, is a species of marine ray-finned fish belonging to the family Antennariidae. It is the only species in the genus Histrio. It lives among Sargassum seaweed which floats in subtropical oceans.

Distribution and Habitat

The Sargassum Fish has a cosmopolitan distribution in tropical and subtropical seas down to a depth of approximately 10 meters. It is found in parts of the Atlantic Ocean and the Indo-Pacific Ocean where drifting seaweed accumulates. In the western Atlantic it ranges from the Gulf of Maine south to Uruguay.

Physical Description

The Sargassum Fish blends well with its surroundings in its seaweed habitat. It is laterally compressed and can reach 20 cm (7.9 in) in length. The coloration of the body and large oral cavity is very variable, usually mottled and spotted yellow, green, and brown on a paler background. The fins often have several dark streaks or bands. The fish can change color rapidly from light to dark and back again. The body and fins are covered with many weed-like protrusions. The dorsal fin has three spines and 11-13 soft rays. The front spine is modified into an illicium tipped with a fleshy esca.

Diet and Feeding

The Sargassum Fish is a voracious ambush predator and also a cannibal. It stalks its prey among the tangled weeds relying on its cryptic camouflage. It dangles its esca as a fishing lure to attract small fish, shrimp, and other invertebrates. It can expand its mouth to many times its original size in a fraction of a second, drawing prey in via suction, and can swallow prey larger than itself. In captivity it should be fed live or frozen foods such as ghost shrimp and small fish.

Behavior and Reproduction

The Sargassum Fish can clamber through and cling to seaweed stalks with its prehensile pectoral fins. It is dioecious. At breeding time the male courts the female by following her closely. The female ascends rapidly to the surface where she lays a mass of eggs stuck together by gelatinous mucus. This egg raft adheres to the seaweed where it is fertilized by the male. This fish can leap above the surface onto mats of weed to avoid underwater threats and can survive for some time out of water.

Aquarium Care

The Sargassum Fish requires a tank of at least 30 gallons with stable water conditions. It is aggressive and will eat any small fish or invertebrate that fits in its mouth. It should be kept singly. It is reef-safe in that it does not bother corals but will consume small tankmates.

Conservation Status

Classified as Least Concern by the IUCN Red List.