The flight surveys were conducted five times during the day in the waters off the southeast coast of Hokkaido where a big catch of sardine Sardinops melanosticta has been taken. In the area sardine schools were easily sighted, but were only distinguished by dark color against lighter background of the sea. To examine a moving direction of school, an experiment was conducted near the fishing ground. In the experiment, it was carried out that floaters fixed to a seamarker were airdropped near a school, and after relative changes between the school and the seamarker were compared each other. The visual observations were conducted 4 times around the fishing ground. The shape of the schools was observed by sight and the number of schools was counted.
From the result of the experiment, it is concluded that the front of the school, which indicates the direction of movement, is dark blue color and the rear is watery blue color. That is, by observing the shape and tone or shade of color of a school, we can easily estimate the moving direction of schools.,
During the visual observations, elongate shape schools have been frequently observed. It is estimated that there were much continuous immigrations from the outside of the small fishing area during before and after the surveys.