The stock status of Japanese common squid Todarodes pacificus has been at a favorable level, but landings in coastal areas of the Sea of Japan have decreased. In the present study, this decrease was examined using monthly landing statistics from Japanese fisheries fiscal years 1994–2008. Landing statistics were examined in four regions: Northern Hokkaido, Southern Hokkaido, Northern Honshu and the Western Sea of Japan. Significant decreasing trends (p<0.01) in the monthly landings were observed during September and October in Northern Hokkaido, July and October in Southern Hokkaido, August and November in Northern Honshu, and May and November in the western Sea of Japan. No increasing trend was observed in any region. Annual rates of decreasing during August and December in Northern Honshu, and during August and September in the western Sea of Japan were approximately 15–25%. These rates correspond to approximately 95–99% over 15 years, which means the fishing grounds disappeared in these regions. Decreasing trends were observed more commonly in southern areas and during summer and autumn. These results suggest that the decreased landings during 1994–2008 might have been linked to the warming of the Tsushima Warm Current that occurred from the late 1990s.

北海道太平洋沿岸における海洋物理環境（水温，塩分，水深）とスケトウダラの産卵場形成との関係を調べた．1月から3月にかけて，表層への沿岸親潮水の流入のため，噴火湾内外の海域（特に日高湾）において水温は低下した．Quotient分析から，スケトウダラの産卵場における平均水温，塩分はそれぞれ4.43°C，33.28で，水塊としては親潮水であった．スケトウダラの産卵場は苫小牧から津軽海峡口へ反時計回りに移動していた．卵が海面で経験する主な水塊は1·2月は親潮水，3月は沿岸親潮水であった．産卵から孵化までの時間は津軽暖流水で8日から20日，親潮水で15日から25日，沿岸親潮水で25日以上であった。これらのことから、水塊の相対的配置は産卵場形成や卵の発生速度に影響していると結論される．最後に，物理環境からスケトウダラの産卵場を推定する方法を提案した.

Repeated observations with ship-mounted ADCP were acquired in Sendai Bay. As the duration of the observations was 9 h, which is shorter than semi-diurnal tidal period, residual current was estimated from the regressed current by the least squares method using the time derivative of predicted tide. The correlation coefficient between observed and regressed current was 0.996 at most. This indicates the de-tiding method of this study is valid. Southward current was dominant in the estimated residual current and the maximum residual current exceeded 20 cm· s^-1. Geostrophic current calculated from observed temperature and salinity corresponded to the residual current. The residual current was likely to be driven by density distribution.