1. Looking at the body shape, most sea crabs are larger than river crabs, and the carapace shape of sea crabs is usually spindle-shaped with sharp edges on both sides, while river crabs are nearly square.

2. Look at the feet. The river crabs on the market are all Yangcheng Lake hairy crabs. The first pair of claws of the crabs have fine hairs. The first pair of claws of the sea crabs are very smooth. The last pair of claws of the river crabs are Pointed claw type, the last pair of legs of sea crabs are usually used for swimming, so they are paddle-shaped.

3. Look at the color. River crabs usually only have one color: blue-grey. Different types of sea crabs have many colors, including green and red flowers.