Shucking oysters and leaving the shells on the public tidelands where they are harvested from is required for the following conservation-based reasons:
Pacific oyster shell provides the best setting and growing substrate for juvenile Pacific oysters. Removing the shells from a beach reduces the overall amount of setting surface, and therefore reduces the potential for new Pacific oysters to set.
Pacific oyster shell also provides an excellent setting surface for the native Olympia oyster. Consequently, removing Pacific oyster shells reduces the potential for native Olympia oysters to set on the beach. This is especially true in places like southern Puget Sound, Padilla Bay and Samish Bay where the natural setting surface - Olympia oyster shells - was eliminated years ago by overharvest.
Removing large, edible-sized Pacific oyster shells from a beach invariably removes tiny Pacific and Olympia oysters which are attached to the larger shells. Thus, removing a legal limit of 18 oysters may actually remove three to five times that number of oysters - young oysters which would otherwise remain on the beach and grow to edible size.
Pacific oyster spat (seed) on oyster shell
Removing oyster shells from beaches containing Japanese oyster drills (an oyster predator present on certain beaches) may result in the inadvertent spread of these predators. Sport harvesters are unlikely to recognize these tiny predatory snails - or their egg cases - which attach to oyster shells and can survive long periods away from water. Once shucked, these shells often end up being returned to a nearby beach by well-meaning harvesters, potentially increasing the spread of the Japanese oyster drill in Washington by depositing the "hitchhikers" on a new beach. Many public beaches already have these tiny predators, but our goal is to minimize their spread to other uninfected public beaches. The surest way to prevent oyster drills or their eggs leaving an infected beach is to require oyster shells to remain on the beach.