Exploitation of Two Critical Predators: The Gastropod Concholepas concholepas and the Rock Lobster Jasus lalandii

In the past three decades considerable research has been devoted to the profound influence of predators on intertidal and shallow-water biotic communities. Amongst other things, this has revealed that predators may act as critical or “keystone species” (Paine 1969), restricting the abundance of competitively dominant species and, thereby, preventing elimination of other species (Paine 1966, 1971, 1974; Dayton 1971; Lubchenco 1978; Peterson 1979; Lubchenco and Gaines 1981). Yet another topic is how predator-prey relationships are maintained in a relatively stable condition, i.e. what prevents the elimination of prey by their predators (Rosenzweig and MacArthur 1963). Possible options include the fact that prey may escape elimination by virtue of size, movement or periodic temporal relief (e.g. Paine et al. 1985; Hockey and Bosman 1988).