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Chlamys chosenica Kuroda, 1932

Common name: Pink scallop and White-pink scallop

Ch. chosenica is a Pacific Asian low-boreal species (Fig. 5). It occurs in the Sea of Japan - along the Primorye coastline; at western Sakhalin Island and northwestern part of Hokkaido Island; in waters of the small Kurile Ridge and Iturup Island. It is registered at depths of 13-2030 m in muddy sands admixed with shingle and gravel; and sometimes in sand or shell rock grounds (Scarlato, 1981). It is quite eurybiontic species occuring at temperature range of near-bottom waters from -0.09 to 13.03 C; salinity range of 33.34-34.15 and oxygen abundance from 5.49 to 7.49 mgl-1 (Myasnikov, 1985). Along the coast of Northern Primorye Pink scallops are mainly colonized by gastropod mollusk Vetulina sp. (Myasnikov, 1986).

According to recent investigations (Silina, Pozdnyakova, 1990), the population of Ch. chosenica from the northern Primorye is represented by mollusks with shell height up to 90 mm, but individuals measuring 68-81 mm predominate. The size distribution of scallops is a one-peaked curve, with a maximum of 77-76 mm. The maximum age of scallops is 22 years, but the population is mostly represented by mollusks of 11-12 years old.

The most intensive linear growth is observed in the first two years and can amount up to 16 mmyr-1. At the age of 3-6, the shell grows by 5.2-10.8 mmyr-1. Then (at the age of sexual maturity), linear growth decelerates markedly and in 10-year-old mollusks comes to 2.5-1.0 mmyr-1 in all. Scallops reach marketable size (60 mm) in about 6 years (Table 1). In the 9-14-year-old scallops with average shell height of 70-79 mm, the muscles weight 7.4-10.4 g. In four years, from 10 to 14 years, the muscle weight increases by not more than 25 % and shell weight at least by 50 %. At the same time muscles comprise 20-25 % of the total weight of the mollusk whenever shells comprise 44-52 %.

The sex ratio (male : female) in population is approximately 1.0 to 1.2. The domination of females (55 %) implicates the stable status of the populations of Ch. chosenica. Spawning of population take place mostly in the first half of summer (Silina, Pozdnyakova, 1990).

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