Chlamys swifti (Bernardi, 1858)

Common name: Swift's scallop

Ch. swifti is a Pacific Asian low-boreal species (Fig. 7). It is distributed along the southern coasts of the Sea of Japan, it also occurs in Western Sakhalin, Hokkaido and northern waters of Honshu Island. In Okhotsk Sea are known from southern Sakhalin (Aniva Bay) and in shallow waters of South Kurile Shoal. The mollusk mainly inhabits the gravel, pebbled and shell grounds at depths of 2-143 m (Scarlato, 1981). This species occurs at temperature range of near-bottom waters from 9 to 22 °C, and salinity range of 32-34 ‰.

According to investigations (Ponurovsky, 1982; Ponurovsky and Silina, 1983), the population of Ch. swifti from the Northern Primorye is represented by mollusks with shell height up to 121 mm. but individuals measuring up to 65-90 mm predominate. The maximum age of scallops is 13 years, but the majority of the population is represented by mollusks up to five years old.

Swift's scallop Ch. swifti grows through all life. However, the most intensive linear growth is observed during the first three years after settling on the bottom and can amount up to 21-26 mm·yr^-1. After this 4 years old, linear growth decelerates markedly and reaches only 1.0 mm·yr^-1 in 8-year-old mollusks (Ponurovsky, 1977; Ponurovsky and Silina, 1983). The highest rates of linear growth of scallops were registered at such regions of the Sea of Japan as Petrov and Putyatin Islands, Vostok Bay (Table 3). Thus these areas are more favorable for intensive growth of Swift's scallop (Ponurovsky, 1982).

The sexual maturity is reached at 3 years where shell height is 50-70 mm. The approximate sex ratio (male : female : hermaphrodite) in the population is 1.0 to 0.67 to 0.02 (Denisova, 1981). At the age of 3 years, males predominate (86.3 %) in the population. Later, males percentage decelerates considerably. At age of 10 years, females predominate (81.2 %) over all in population.

At Peter the Great Bay and Bousse lagoon (southern Sakhalin I.) larvae are abundant in plankton from August to September at a water temperature of 15-20 °C. The maximum density of larvae occurs at near-bottom waters in bathymetric range of 10-20 m (Kas'yanov et al., 1983). The morphology of larvae and larval shell structure were described by V. A. Kulikova with co-authors (1981). The optimal depth for spat collection exceeds 15 meters (Gabaev, 1988).

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