The present paper deals with patterns in spatial distributions of pelagic fish (Engraulis japonica, Trachurus japonicus, Scomber japonicus, Etrumeus micropus and Sardinops melanosticta) in coastal waters. It is based on the daily catch data obtained by eleven small purse seiners. It was found that commercial fishery could act as an efficient sampling method to study movements of fish group at a level of elementary population. Each species of the pelagic fish always constituted a separate and stable group, elementary population with a size of between 6 km and 11 km in an average diameter. Careful examinations of daily maps showing the distribution of each fish species suggested the presence of interrelationships between groups of pelagic fish.