The Bay of Bizerta (Tunisia) has some sheltered rocky areas that support an important lithophagous fauna. The hard rocky limestone substrata in the bay showed a well-ordered mineralogical structure and the biomicritic matrix contained benthic Foraminifera and ostracod remains dating from Eocene. Monitoring the rocky benthic communities over a period of one year enabled us to study the behavior and the ecology of Lithophaga lithophaga and its associated fauna. The population of this lithophagous bivalve is threatened by unauthorized collecting and the rocky sites are seriously damaged by human activities. The number of individuals of L. lithophaga varies considerably, from one rock block to another, depending on the position and the shape of the substratum. This species usually dominates the zoobenthos community and the associated fauna comprises 29 species (between October 2002 and September 2003). This fauna consists of 8 faunistic groups (Bivalvia, Gastropoda, Polyplacophora, Sipunculoïda, Crustacea, Polychaeta, Echinoderma, and fish).