Distribution of Japanese Sandfish Arctoscopus japonicus (Steindachner, 1881) (Trichodontidae) in Peter the Great Bay (Japan Sea) with Respect to Environmental Conditions

摘要

General distribution patterns for japanese sandfish Arctoscopus japonicus in Peter the Great Bay in spring, summer, and fall, which are related to the water structure, are determined from the bottom trawl survey data. When the larval stage is finished, the sandfish underyearlings appear in trawl catches since July and are recorded at the depths of 23-60 m in July-August at water temperature of 8-16 degrees C. Judging from localization of catches at the upper benthic front, they lead a pelagic mode of life in summer, concentrating above the seasonal pycnocline, so belts of high catches by bottom trawl are located along the line of pycnocline contact with the bottom. In the fall season, the underyearlings pass to bottom dwelling below the upper benthic front. The adults dwell permanently at the bottom, in the subsurface shelf waters. Their feeding starts near the coast in May-June, avoiding the remnants of the cold bottom shelf water, and they gradually retreat deeper in July-September. Prespawning aggregations are formed at the shelf edge and on the upper continental slope in October. The spawners migrate to the coastal zone in November for spawning on seaweeds. For wintering, the sandfish adults may leave Peter the Great Bay, moving to the more southern areas.