Relationship between Saury Fishing Grounds and Large-Scale Coherent Structures in the Ocean, According to Satellite Data
Using satellite data on the speeds of geostrophic currents AVISO from 2004 to 2018, we associate a significant reduction in saury catch in the recent years with a change in the oceanographic situation in the Russian fishery area off the coast of the southern and middle Kuril Islands and Hokkaido Island. The Lagrangian maps of the origin of water masses, calculated for this period of time on the basis of the AVISO field, with overlaid positions of fishing vessels of Russia, Japan and Korea, show that this catastrophic decrease is caused by a change in the pathways of nutrient-rich subarctic waters of the Oyashio current in the recent years. The most significant changes of the hydrological regime since 2015 were caused by an intensification of the 3rd branch of Oyashio, which transports the waters of this current to the open ocean. At the same time, the traditional fishing grounds off the eastern coasts of Hokkaido and southern Kurils significantly reduced, whereas favorable fishing grounds appeared in the open ocean.