Shellfish, despite their name, are not actual fish. They are typically low on the food chain and mainly feed on phytoplankton and zooplankton. Many shellfish, particularly crustaceans, are closely related to insects and arachnids within the phylum Arthropoda. Mollusks include cephalopods (like squids and octopuses), bivalves (such as clams and oysters), and gastropods (which encompass both aquatic species like whelks and land species like snails).
