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<p>Top-down effects of predators in systems depend on the rate at which predators consume prey, and on predator&nbsp;preferences among available prey. In invaded communities, these parameters might be difficult to predict because&nbsp;ecological relationships are typically evolutionarily novel. We examined feeding rates and preferences of a crab native to the&nbsp;Pacific Northwest, <em>Cancer productus</em>, among four prey items: two invasive species of oyster drill (the marine whelks&nbsp;<em>Urosalpinx cinerea</em> and <em>Ocenebra inornata</em>) and two species of oyster (<em>Crassostrea gigas</em> and <em>Ostrea lurida</em>) that are also&nbsp;consumed by <em>U. cinerea</em> and <em>O. inornata</em>. This system is also characterized by intraguild predation because crabs are&nbsp;predators of drills and compete with them for prey (oysters). When only the oysters were offered, crabs did not express&nbsp;a preference and consumed approximately 9 juvenile oysters per crab per day. We then tested whether crabs preferred adult&nbsp;drills of either <em>U. cinerea</em> or <em>O. inornata</em>, or juvenile oysters (<em>C. gigas</em>). While crabs consumed drills and oysters at&nbsp;approximately the same rate when only one type of prey was offered, they expressed a strong preference for juvenile&nbsp;oysters over drills when they were allowed to choose among the three prey items. This preference for oysters might negate&nbsp;the positive indirect effects that crabs have on oysters by crabs consuming drills (trophic cascade) because crabs have&nbsp;a large negative direct effect on oysters when crabs, oysters, and drills co-occur.</p>