To judge whether the frozen swimming crab is fresh, we should first look at the color of the crab. The dead swimming crab is dark and the fresh swimming crab is bright. Secondly, I smell crabs. Fresh crabs are cooked with the faint fragrance of seafood dishes, but the stale crab meat is rotten, and it has a pungent smell when cooked. Finally, pinch the texture of the crab. The shell of the fresh Portunus trituberculatus is hard and full when cooked, and it will not sag when pushed by hand. The shell of the stale Portunus trituberculatus becomes soft and the inside becomes empty.

Swimming crab, commonly known as "white crab" in some places. Because the breastplate is shuttle-shaped, it is named shuttle. There are three protrusions in the center of the carapace, so it is also called "Portunus trituberculatus" and belongs to arthropods. Male umbilicus is smooth, with long claws and bluish shell surface; The female umbilical cord is round and fluffy, and the shell surface is ochre or spotted. Portunus trituberculatus meat is delicious and has high nutritional and economic value, and is suitable for temporary cultivation and fattening in seawater.

Distributed in Japan, Korea, Malay Archipelago, Red Sea and most of the coastal areas of Chinese mainland.