Mizuhopecten yessoensis

Lore & Background

The Yesso scallop has a convex center with a smooth exterior shell, white on one side and dark brown on the other. It is widely distributed along the cold coast of Northern Japan, with scallop cultivation located in the northern islands of Honshu and Hokkaido. The Sea of Okhotsk, Saroma Lake, and Funka Bay in Hokkaido accounted for more than 80% of scallop production from 1991 to 2002.

Temperature plays a key role in spawning and larvae settlement. Spawning occurs between May 1 and June 9 over 10 days, with later commencement when surface water remains below 0°C for a prolonged period. Lower temperatures in April and a shortened pre-spawning period also contribute to later spawning. Larvae settlement typically occurs between June 4 and July 5 over 15 days, with colder pre-spawning periods delaying settlement. The upper limit for scallop development is 18°C.

Growth varies with temperature: in warm water below 18°C, scallops grow most rapidly between ages 2 and 4; in colder environments, peak growth occurs between ages 3 and 5. The lowest mortality rate is between ages 2 and 5, rising dramatically from ages 6 to 7. Main predators are the sea stars Asterias amurensis and Distolasterias nipon, with D. nipon having a greater influence on predation. Smaller scallops and those in warmer waters are more likely to be preyed upon.

Reader's Guide

Mizuhopecten yessoensis is significant as a commercially cultivated species in northern Japan, with over 80% of production from 1991 to 2002 concentrated in Hokkaido's Sea of Okhotsk, Saroma Lake, and Funka Bay. Its tissues bioaccumulate algal yessotoxins, making it a subject of extensive study. The scallop's spawning and settlement timing are tightly linked to water temperature, with prolonged cold delaying both processes. Growth and mortality rates are also temperature-dependent, with optimal growth between ages 2 and 5 and a sharp mortality increase after age 6. Predation by sea stars, particularly Distolasterias nipon, affects smaller individuals and those in warmer waters. In Japan, the adductor muscle is eaten raw as sashimi and sushi under the name hotate-gai; in China, it is sometimes dried to make conpoy, often called 'Japanese conpoy.' The species' ecological and economic roles are closely tied to cold-water environments and temperature dynamics.