The western North Pacific is one of the most important fishing ground around Japan. Fisheries Research Agency established the observation line“A-line” to monitor the physical and biological environment in 1987 in this waters. The monitoring has been continuously carried until present. The “A” of A-line was derived from Akkeshi where is the nearest town of the start station of the line. The monitoring was started by the Hokkaido National Fisheries Research Institute. Tohoku National Fisheries Research Institute joined the monitoring in 2002 and the two institutes have been carried out the monitoring in collaboration until now. Although the water temperature, salinity, chemical component such as nitrate, and plankton are regularly observed, other items such as rare chemical components and micro nekton are also observed as needed.
The recent studies suggested that the climate change relates to the large scale variation of fish resources and marine ecosystems. The long-term data is necessary to investigate the relationship based on observation data. The data obtained by A-line monitoring is used for the studies which aim to reveal the relationship between climate change and ecosystems by not only domestic but also foreign institutes.