The Response of an Intertidal Concholepas concholepas (Gastropoda) Population to Protection from Man in Southern Chile and the Effects on Benthic Sessile Assemblages

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Abstract
In this paper we document the changes experienced by the carnivorous Concholepas concholepas snail population after the establishment of a marine reserve in May 1978. Our data indicate that the release from human predation results in a striking change of the Concholepas population structure, due to the increment of individuals larger than 40-50 mm peristomal length. This evidence strongly indicates that the usual absence of larger size classes from the intertidal is not a consequence of physiological limitations of the muricid, as was previously thought. Significant density differences were detected only in 1984, but they were due to substantial reduction of the snails in the harvested control area. The reduction experienced by Concholepas prey species (barnacles and Perumytilus purpuratus) in the marine reserve area during the same period, indicates that the carnivore has an important role in the organization of the intertidal benthic sessile assemblage. Although, our results support the idea that in the absence of human intervention of intertidal community structure differs from the usual, previously considered "natural" structure.