* Fish belong to the class Actinopterygii (ray-finned fishes) or Chondrichthyes (cartilaginous fishes). They are vertebrates with backbones, fins, and gills for breathing underwater.
* Shellfish belong to the phylum Mollusca (like clams, oysters, mussels, and snails) or the phylum Arthropoda (like crabs, lobsters, and shrimp). They are invertebrates meaning they lack a backbone.
Here's a breakdown of their key differences:
| Feature | Fish | Shellfish |
|---|---|---|
| Biological Classification | Vertebrates | Invertebrates |
| Backbone | Present | Absent |
| Breathing | Gills | Breathe through gills or skin |
| Skeleton | Bone or cartilage | Exoskeleton (shell) |
| Movement | Fins | Legs, claws, or swimming appendages |
| Examples | Salmon, Tuna, Cod, Shark, Eel | Clams, Oysters, Mussels, Crabs, Lobsters, Shrimp |
In essence:
* Fish are aquatic vertebrates with fins and gills.
* Shellfish are aquatic invertebrates with shells or exoskeletons.
While they share the common characteristic of being aquatic, their fundamental biological differences place them in distinct categories.