For the audience or readers to deepen understanding of fisheries oceanography, especially physical fisheries oceanography, this lecture reviews my research work, including clues, failures and management problems encountered during the course of my studies. The contents of this lecture are: (1) introduction, (2) hydrographical feature in and around the Perturbed Area between the Kuroshio and Oyashio Fronts and its fluctuation, (3) conservative properties along a streamline or a trajectory and observation planning, (4) the Kuroshio south of Japan and warm and cold eddies pinched off from the Kuroshio meanders, (5) convergence-divergence of currents and accumulation-dispersal of marine organisms, (6) the Japan Sea (and a part of the East China Sea), and (7) conclusion: approaches to research in fisheries oceanography.