The ecological role played by man as a top predator in rocky intertidal environments has been largely overlooked in the literature. Although several publications have dealt with the rocky intertidal assemblages of cen-tral Chile (Guiler 1959a, b, Alveal 1971, Santelices et al. 1980, Castilla 1981, Paine et al. 1985) they have neglected in all but a few (ie Moreno et al. 1984) this role.

Castilla (1981) noted high densities of the limpet-like carnivorous muricid gastropod Concholepas conchole-pas intertidally in a stretch of rocky shore line with lim-ited human perturbation at Peninsula El Salto, Los Molles (for details see also Castilla and Bahamondes 1979). These observations suggested that this species might play a key ecological role on rocky shores where it is not harvested. For example the study site at Los Molles showed an almost total absence of some com-mon, competitively dominant species such as the mussel Perumytilus purpuratus, a prey species of intertidal Concholepas (Castilla et al. 1979, Guisado and Castilla 1983). Since localities such as Los Molles with little or no human interference are difficult to find in central Chile it has become necessary to perform long-term man exclusion manipulative experiments (sensu Hurl-bert 1984) if possible human effect are to be identified and understood. In this way the natural role of this species, particularly prized for human consumption, can be discovered as well as contributing to the understanding of rocky intertidal community structure and dynamics in the absence of human interference. Concholepas concholepas, known in Chile as" loco", is a unique gastropod present only along the Chilean and part of the Peruvian coasts (Stuardo 1979). It is a traditional shellfish species of great economic importance in Chile (Castilla 1982). In 1980 a record 24856 metric tons were fished (mostly subtidally and using di-ving techniques) in this country. Castilla (1982, 1983) summarized the papers published so far on the species. Guisado and Castilla (1983) rewieved some of the ecology and growth of an intertidal juvenile population of locos in central Chile.