Abstract: The present invention provides a feeding stimulator for fishes and shellfishes, selected from the group consisting of dimethyl-.beta.-propiothetin and certain compounds related thereto or salts thereof, and a feed to which this feeding stimulator has been added. The above feeding stimulator has the action of stimulating gustatory sense or olfactory sense of fishes or shellfishes to promote their appetites. Hence, employment of a feed to which this feeding stimulator has been added enables enhancement of feed efficiency in aquaculture or the like of fishes and shellfishes. Also, even when a substitute feed available in a low cost is used, it becomes possible to maintain the same feed efficiency as the mixed feeds in which raw feeds and fish powder are used.