Climate-Related Variations in Autumn Cohort of Japanese Common Squid Todarodes pacificus

The Japanese common squid Todarodes pacificus is widely distributed in the Sea of Japan,the East China Sea and the Northwest Pacific Ocean,and is largely exploited by the Asia-Pacific countries.In this study,the impacts of regime shift of the Pacific Decadal Oscillation(PDO)during 1977-2015 on the autumn cohort of T.pacificus were assessed by examining the variations in vertical water temperatures at depths of 0 m(Temp_0 m),50 m(Temp_50 m)and 100 m(Temp_100 m)and the distribution pattern of preferred spawning ground(SSG).Spatial and temporal correlation analysis revealed that the PDO index exhibited a significantly negative relationship with vertical water temperatures at different depths and was negatively related to catch-per-unit-effort(CPUE)and stock biomass of T.pacificus.In addition,water temperatures in the specific three water layers were positively associated with CPUE.The PDO regime shift strongly affected the thermal condition and spawning ground of T.pacificus.Comparing to the negative PDO,the waters from the surface to the deep became cool in the positive PDO phase;correspondingly,the area of SSG largely contracted at different depths.Consequently,the CPUE and stock biomass of T.pacificus profoundly decreased.From the results it can be concluded that the PDO regime shift-driven changes in vertical thermal condition and SSG ranges can yield substantial impacts on T.pacificus abundance.

Effects of Climate Variability on Habitat Range and Distribution of Chub Mackerel in the East China Sea

Spatio-temporal distribution of chub mackerel Scomber japonicus is strongly susceptible to climate variability.In this study,a weighting-based habitat suitability index(HSI)model was established to assess the impacts of Pacific Decadal Oscillation(PDO)on habitat range and distribution of S.japonicus in the East China Sea(ECS)using vertical water temperature at depths of 2.5 m,25 m and 50 m.Results showed that the optimal HSI model selected from ten weighting scenarios can yield reliable predictions.Correlation analysis revealed a significant negative relationship between the PDO index and water temperature anomaly at different depths.The water temperatures at three different layers on the fishing ground of S.japonicus tended to be low in the warm PDO phase and high in the cold PDO phase,respectively.The range of suitable habitats and its spatial distribution exhibited large differences between the warm and cold PDO regimes.During a warm PDO phase,vertical water temperature became cool,and the monthly preferred water temperature at each depth for S.japonicus shifted southeastward.Consequently,habitat quality dramatically decreased,and suitable habitat ranges also reduced and moved southeastward.Conversely,in a cool PDO phase,with the warmer vertical water temperature and northwestward shift of the preferred water temperature,the suitable habitats enlarged and migrated in the same direction.Our findings indicate that the PDO produced significant impacts on habitat range and distribution of S.japonicus in the East China Sea.