Abundance and Distribution of Pelagic Larvae of Bivalves and Echinoderms in Busse Lagoon (Aniva Bay,Sakhalin Island)

The taxonomic composition and numbers of pelagic larvae of bivalves in Busse Lagoon and the contiguous areas of Aniva Bay (southern Sakhalin) were studied in 2000–2001. In comparison with 1973–1974, the total density of larvae increased 2–3 times, but their taxonomic composition changed and a redistribution of dominant species occurred. Numbers of bivalve larvae increased at the expense of larvae of Musculista senhousia, Crassostrea gigas, and species of the Tellinidae. In 2000–2001, larvae of Ruditapes philippinarum, Mya arenaria, Swiftopecten swifti, and some other species were encountered in plankton very rarely or were not found at all. The drastic decrease in the larval density of some bivalve species was caused by uncontrolled and nearly total harvesting of mollusks. Larval echinoderm numbers in the lagoon were not high in 2000–2001; larvae of the sea cucumber Apostichopus japonicus and the sea urchin Strongylocentrotus intermedius predominated.