1, fresh fish can be torn from the head of the mouth with a few setbacks toward the tail.

2, if the tearing is laborious or even the flesh of the fish sticks down, it means the fish is not fresh and has been repeatedly frozen.

Good sole body lateral compression, long tongue, eyes are often located on the left side of the head, caudal hyoid longitudinally narrow plate, there is a pseudo-intermediary medullary spine, odd fins are completely connected to the pectoral fins, no pectoral fins, abdominal fins 1 and even the anal fins, the genital protuberance is often connected to the left side of the anal fins, the renal vein spine short transverse plate-like, eggs have small oil balls 50 to 100.