what are shellfish

Shellfish are aquatic invertebrates that have a shell or shell-like exterior. They are used as food and can be divided into two groups: crustaceans and mollusks. Crustaceans include shrimp, crayfish, crab, and lobster, while clams, scallops, oysters, and mussels are examples of mollusks. Some species of shellfish are harvested from saltwater environments, while others are found in freshwater. Despite the name, shellfish are not fish, and most of them are low on the food chain and eat a diet composed primarily of phytoplankton and zooplankton. Shellfish are rich in lean protein, healthy fats, and minerals, and regularly eating them may boost immunity, aid weight loss, and promote brain and heart health. However, shellfish are one of the most common food allergens, and some types may contain contaminants and heavy metals.