Final answer:
Shellstock tags must be kept on file for 30 days after the container has been emptied or the last shellfish was served.
Step-by-step explanation:
When it comes to shellstock tags, they must be kept on file for a specific period to ensure traceability and safety. According to the U.S. Food and Drug Administration (FDA), shellfish must be accompanied by a shellstock tag from the approved source until the container is empty or the last shellfish is served. After this, the shellstock tags must be kept on file for 30 days.
During these 30 days, the shellstock tags act as a record that can be accessed for auditing purposes and to track any potential issues or contaminants. It is important to maintain these records to ensure the safety and quality of shellfish.