Catch properties of jack mackerel, Trachurus japonicus, in the Bungo Channel, where is well-known for an intrusion of warm water from the Pacific Ocean, were examined from the seasonal-regional relationship between variation of age-0 jack mackerel landings and hydrographic conditions. Age-0 jack mackerels were caught from May through October in the central region of the Bungo Channel, while in the southern region they were caught throughout the year. This seasonal-regional difference of the catches in the channel is probably caused by the warm water intrusion associated with the development of stratification in the central region. It is therefore suggested that the age-0 jack mackerels in the southern region move to north with the intrusion of warm waters. It was also distinct that the catches of jack mackerel in the central region strongly depended on a spring recruitment originated from the southern region. Sampling of jack mackerel larvae revealed that the intrusion of warm water in April was accompanied by the inflow of the jack mackerel larvae from the southern region. Inter-annual catch variation of age-0 jack mackerel in the southern region was found to be caused by the generation of the Kuroshio frontal eddy off the Channel.

An advection and diffusion model for particle tracking in three dimensions and the deployments of satellite-tracked drifters were conducted to examine the role of the Kuroshio front on the transport process of jack mackerel larvae in the East China Sea (ECS) in early spring. Larvae of jack mackerel transported from the shelf area remained largely in the ECS, and survival rate for them was estimated to be very high through the experiments adopting mortality dependent on temperature and salinity. It was also verified that the Kuroshio front played a significant role as a boundary in the transport processes of jack mackerel larvae. Furthermore, trajectories of satellite-tracked drifters released in the Kuroshio frontal region and over the shelf area supported that transport processes are significantly different according to the releasing locations which was suggested by the advection-diffusion model. It was also revealed that passive larvae from the Kuroshio frontal region showed a low survival and a cyclonic flow due to frontal disturbances southwest of Kyushu acts as a main mechanism in transporting them into the waters off western Kyushu (WWK), where has a good feeding condition. Therefore, it is probably important the passive larval transport from the Kuroshio frontal region into the WWK for the good survival.

In order to quantify the water purification function of a macrobenthic community, the concentrations of nutrients in overlying water were monitored hourly using the tidal flat experimental facility at Aichi Fisheries Research Institute, which reproduced physical environmental conditions such as tidal level, tidal currents, waves, and winds. The experimental ecosystem supported a macrobenthic community dominated by bivalves. All the nutrient elements (NH₄–N, NO₂–N, DON (dissolved organic nitrogen), PON (particulate organic nitrogen), PO₄–P, and DOP (dissolved organic phosphorus)) except for NO₃–N in the water column were removed. The calculated removal rate of PON by the macrobenthic community (50 mgN·m^－2· day^－1) was found to be similar to that estimated by an alternative simple index, or PONrm (41 mgN·m^－2· day^－1), which had been devised based on the biomass of the macrobenthic community, and standing stock of chlorophyll a and pheo-pigment in an earlier study conducted by our research group. This finding suggests that PONrm is a simple and proper index for quantifying the water purification function of macrobenthic communities.