An a-priori evaluation model for restoration of fisheries population of the Manila clam and a countermeasure example in Ise Bay

摘要

The national production of the Manila clam, Ruditapes philippinarum, fishery has been continuously declining since the mid 1980s in Japan. The total production of asari in Ise Bay exceeded 10,000 tons per year in 1980s. However, it started to decreasein the mid 1990s, and it has been less than 5,000 tons. Fisheries Agency of Japan has been implementing stock enhancement programs, including fisheries management, fishing ground development and reseeding as countermeasures for the production decline. In order to attain successful stock enhancement, it is first of all necessary to elucidate the causes of stock depletion in each stage in life cycle of the clam. Then, one must make a plan to remove or reduce the effects of the elucidated causes taking into account what measures should be applied to what location to what extent. In the present study, we introduce about two topics. First topic is about the development of an a-priori evaluation model for restoration of the asari clam in Ise Bay. And the second topic is an example of countermeasure for asari stock recovery in Ise Bay. In Ise Bay, asari juveniles often do not survive until adult stage. So we have developed an effective juvenile collection method for transplantation and we are trying to develop a nursery ground for high growth and low mortality of asari.