ABSTRACTOpen‐ocean mariculture might have considerable advantages in large‐scale production over usual tank and closed‐bay techniques. Most of the benefits would lie in the elimination of closed systems which require extensive power for water circulation and are subject to the rapid spread of chemical pollutants and disease. In tropical and subtropical waters pelagic sargassum is suggested as a medium for mariculture. Sargassum could be utilized in shallow water as cover, with the concomitant life forms (i.e. plankton, crustaceans, etc.) as a food supply for juveniles such asCoryphaenasp. Some benthic forms, molluska for example, might produce higher yields under cover of sargassum than on reefs or platforms. Studies could also be made on the relationship of seaweed to eels and turtles with a view towards developing culture methods. Deep water platforms might be based under the sargassum mass to eliminate pollution problems associated with nearby land masses.As a byproduct of mariculture, the sargassum would provide the basis for a local alginate extraction ind