Rev. biol. mar. oceanogr. 48(3): 431-450


A trophic characterization of intertidal consumers on Chilean rocky shores

Patricio A. Camus1, Paulina A. Arancibia1,2 and M. Isidora Ávila-Thieme1,2

1Departamento de Ecología, Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Casilla 297, Concepción, Chile
2Programa de Magister en Ecología Marina, Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Casilla 297, Concepción, Chile

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In the last 50  years, the trophic role of consumers has become a main research topic in the ecology of Chilean rocky shores, and in other regions. Several studies have typified species of echinoderms, crustaceans and mollusks as the most important herbivores and carnivores of intertidal assemblages. Unfortunately, little is known about the diet and behavior of many consumers, making difficult addressing key issues related to the importance of omnivory, intra- and inter-specific competition, or individual specialization. The goal of this paper is to fill some gaps in the available information and provide researchers with an exhaustive dietary analysis and relevant ecological descriptors for a suite of 30 consumer species distributed along the southeastern Pacific coast. Our data integrate information collected through seasonal samplings conducted between 2004 and 2007 at 4 localities distributed over 1,000 km of coast in northern Chile. Based on laboratory and field work analysis, we present: (a) a consumer-resource matrix obtained from high-resolution analyses of gut contents of 6,377 individuals, including 222 prey items (80% identified at species or genus level); (b) estimates of the density, body size (length and weight), diet width (at individual and species levels), and within-individual diversity of consumer species; (c) an nMDS ordination of the compositional similarity of consumers’ diets, and information on the relative importance and occurrence frequency of the most common preys of each consumer. Based on the high frequency of omnivory and the high diet overlap among consumers, we discuss their potential for competition and the role of individual specialization in shaping their generalist character, highlighting the need to reappraise their behavior and ecological effects in the intertidal community.

Key words:  Diet, niche width, individual specialization, omnivory, body size