MANAGEMENT POLICIES OF YEZO ABALONE NORDOTIS-DISCUS-HANNAI FISHERY UTILIZING INFORMATION ON SEA-WATER TEMPERATURE AND STOCK SURVEY

This paper studies management policies for the Yezo abalone Nordotis d iscus hannai on the coast of Iwate Prefecture, northern Japan. The abn ormally low sea water temperature periodically observed is thought to be related to the mortality of the abalone. A stock survey was carried out to design an effective management policy. Based on predictions of the sea water temperature and the results of the stock survey, we pro pose a management policy which controls the fishing mortality coeffici ent and the number of juveniles released. Simulations were conducted u sing estimated or assumed values of biological and operational paramet ers. Within the range of parameters used here, the results suggest the following: (1) The utilization of both sea water temperature and stoc k survey provides more accurate catch predictions than when using only sea water temperature. (2) When the sea water temperature is predicte d accurately, decreasing the number of juveniles released and increasi ng the fishing if the stock is good brings good cathches.