Final answer:
It is not safe to accept shellfish that are labeled as frozen but received thawed, as the risk of bacterial growth and potential foodborne illness is high.
Step-by-step explanation:
When handling frozen shellfish, it's important to adhere to food safety protocols to prevent foodborne illness. According to the US Department of Agriculture (USDA), frozen foods should maintain certain temperatures to inhibit bacterial growth. If shellfish labeled as frozen are received thawed, they should not be accepted. Thawed shellfish can pose a risk since the bacteria that were dormant may start to grow again, making the shellfish unsafe to eat. Furthermore, freezing at temperatures below -2 °C is essential to ensure the elimination of parasites and worms from the food.