We have worked with a major clam and oyster farming operation, harvester and packer. They ship raw fresh unshucked and also shucked clams and oysters in plastic buckets and #10 metal cans.
The facility has never had a metal detector and based on a written risk assessment none was needed and they passed their SQF audit with flying colors. What they do have however is an extensive laboratory operation for potential pathogens and to safe guard the health of their 300,000 acres of aqua-farming beds.
An additional client on the Gulf of Mexico pasturizes (using water) their oysters and also sells frozen and fresh oysters in shell as well as banded.
They also do not have a metal detector.
I see no basis for a metal detector your operation.
The only "warning" on the package (and mesh bagged label) is that oysters and clams may contain sand particles.