The mere fact that operations preparatory to canning are physically separated from the main canning operations of hermetically sealing and sterilizing or pasteurizing would not be sufficient to remove them from the scope of section 13(b)(4). Where preparatory operations such as the steaming or shucking of oysters are performed in an establishment owned, operated, or controlled by a canner of seafood as part of a process consisting of continuous series of operations in which such products are hermetically sealed in containers and sterilized or pasteurized, all employees who perform any part of such series of operations on any portion of such aquatic products for canning purposes are within the scope of the term “canning.”