Sandeel fisheries in Japan have developed in consequence of the expansion of fish culture. The mean annual catch of sandeel during 1968-'76, when aquaculture had fully evolved, reached 210,000 t. More recently the catch has declined to a level of about 140,000 t. This seemed to be the result of overfishing. At the same time, however, the sandeel productions in Sendai Bay has been on the increase since 1977. This was the result of the development of new fisheries by boat seines since 1977 and trawlers since 1984. The sandeel resouce in Sendai Bay has had such a reproductive system as repeats a 3-year cycle of aboundance. The range of landing fluctuation during that period was narrow, and a state of equilibrium seemed to prevail. However, with entry of the above-mentioned fishing gears, pressure on the sandeel resource was increased greatly. As a result dominant year-class burst on 1978 and 1987 which were not cyclic dominant years birth of sandeel. Therefore it is assumed that the reproductive system of sanded has been changing. From analysis of fishery statistics, it would seem that the resource has declined as a rsult of the recent increase in catch. It is desirable to establish a management program to identify the optimum level of fishing effort exploitation of sandeel resource.