Molluscs whose shells may be opened by "shucking” them (7)
I believe the answer is:
oysters
(Other definitions for oysters that I've seen before include "Fleshy bivalves, may yield pearls" , "Yet Ross, strangely, has the marine creatures" , "Succulent bivales" , "Edible bivalve molluscs" , "Yet Ross can find the marine creatures" .)