Aggressiveness of Stegastes adustus towards humans and other S. adustus

Four sites were assessed in Discovery Bay, Jamaica to monitor the aggressive behavior of the Dusky damselfish, Stegastes adustus: two sites by the jetty, one by the limestone rock area and one by the mangrove. All four sites were specifically chosen because of its sufficiency in its food supply, algae.  The purpose of this study is to observe the territorial behavior of S. adustus and recording whether the damselfish reacts more aggressively to humans or to its own kind. Within all of the four sites, two controls were performed using an empty plastic jar, as well as seven trials of  human interaction, and seven trials of another damselfish placed in the container.  On a reaction scale that measures the level of aggression from 1 to 5, the damselfish were most aggressive towards another damselfish in all of the four sites. The first site of the jetty experienced the highest level of aggression. Its aggression level reached a level 5 (physically attacking the object), when the object was within zero feet of its territory. This area also showed a higher level of aggressiveness towards humans as compared to the other three sites – an average of a level 4 behavior. The damselfish were least aggressive towards another damselfish in the limestone rock area and the mangrove. Both sites encountered an average of level 3 behavior (flapping of their fins). This project suggests that the S. adustus are highly aggressive. Regardless of the ample food supply that is has in its territory, it still reacts more aggressively to its own kind than it does to humans.

Jenna and Paulie