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Potential effects of a non-indigenous predator in its expanded range: assessing green crab, Carcinus maenas, prey preference in a productive coastal area of Atlantic Canada

Pickering, Tyler, Quijón, Pedro A.
Marine biology 2011 v.158 no.9 pp. 2065-2078
Carcinus maenas, Crassostrea virginica, Mya arenaria, Mytilus edulis, clams, coasts, crabs, feeding preferences, mussels, oysters, predators, Canada
The non-indigenous green crab (Carcinus maenas) is an important predator on bivalve wild beds in coastal areas worldwide. This study explored size-dependent green crab prey preference on American oysters (Crassostrea virginica), blue mussels (Mytilus edulis), and soft-shell clams (Mya arenaria) in a productive coastal system of Atlantic Canada. Using two sizes of prey and three different experimental manipulations, small, medium, and large green crabs were given a choice among these three bivalves, and their daily feeding rates were monitored over the course of 3 days. For both prey sizes, green crabs showed an early feeding preference for soft-shell clams and, only as they declined in numbers, a switch toward mussels and subsequently toward oysters. We found that such changes in the timing (order) of prey preference are related to prey differences in shell thickness, a fairly reliable indicator of prey shell strength.