Yesso, Farrer's and bay scallops: telling apart three common northern scallops

On the farms and in the seafood markets of the Liaodong and Shandong peninsulas, three scallops are the most common. All belong to Pectinidae, and side by side they are not hard to separate: look at size, the two auricles (ears) and the colour of the two valves. (Editorial sample article; admins can edit or delete it.)

Yesso scallop Mizuhopecten yessoensis

• The largest of the three; adults often exceed 10 cm in shell height.
• The two valves differ clearly in colour: the right (lower) valve is more convex and yellowish-white; the left (upper) valve is flatter and purplish-brown.
• The front and rear auricles are nearly equal.
• Native to Hokkaido and the Russian Far East; a cold-water species introduced to northern China for farming in the 1980s.

Farrer's scallop Azumapecten farreri

• Small to medium; adults mostly 6–8 cm in shell height.
• Auricles clearly unequal: the front one is large, the rear one small; below the front auricle of the right valve is a byssal notch with a small comb of teeth, which gives the Chinese name.
• The ribs often carry small spines; colour varies widely, from purplish-brown to orange-red to yellowish-white.
• Native to northern Chinese coasts; formerly Chlamys farreri.

Bay scallop Argopecten irradians

• Medium-sized, with both valves convex so the shell looks "puffed".
• About 17–20 rounded, even radial ribs.
• Auricles nearly equal; shell mostly greyish-brown with mottling.
• Native to the US Atlantic coast; introduced to China in 1982, fast-growing, and an important farmed species in the north.

Photo tips

If a photo shows both auricles and both valves, these three can usually be told apart. Seed and hybrid scallops may not show typical features, so note the origin when you upload and use molecular ID when needed.