Experiments were conducted to determine whether locally abundant crab species prefer co-occurring littleneck clams, Protothaca staminea (Conrad, 1837) and Tapes philippinarum (A. Adams and Reeve, 1850), relative to a recently introduced species, the varnish clam, Nuttallia obscurata, (Reeve, 1857). Prey preference, handling time, pick-up success, profitability and consumption rates were investigated for two crab species, Dungeness crab, Cancer magister (Dana, 1852) and red rock crab, Cancer productus (Randall, 1839) crabs. Both crab species preferred varnish clams over the native species. This may be attributable to the lower handling time, higher pick-up success and increased profitability of consuming varnish clams. Handling time appeared to be a factor not only in species preference, but also in the degree of preference, with shorter handling times corresponding to stronger preference values. Both native and introduced bivalves burrow into the substratum, with the varnish clam burrowing deepest. When feeding on clams in limited substratum both crab species preferred the varnish clam. In the unlimited substratum trials Dungeness crabs preferred varnish clams (although to a lesser degree) while red rock crabs preferred littleneck clams. This was likely due to the significantly deeper burial of the varnish clam, making it less accessible. Although the morphology (i.e. thin shell, compressed shape) of the invader increases its vulnerability to predation, burial depth provides a predation refuge. These results demonstrate how interactions between native predators and the physical characteristics and behaviour of the invader can be instrumental in influencing the success of an invasive species.