Estimation of secondary production by razor clam, Sinonovacula constricta, in muddy tidal flat inner part of Ariake Bay, Kyushu Japan

Abstract

Although Sinonovacula constricta used to be a major clam that was caught in the muddy tidal flats in Ariake Bay until the 1980s, the harvest drastically decreased in the 1990s. Saga Prefecture took measures to recover the fishery resources by releasing clams to enhance the cycle of reproduction between 1997 and 2018, and the released young clams showed remarkable, stead growth with high biological productivity. In this study, we investigated the survival rates and the growth of juvenile clam after released in four tidal flats. Moreover, we explored the relationship between the tide height and the secondary production based on those results. According to the results of this study, the biomass could reach up to 4,698 g Wet Weight (gWW)/m². In addition, the amount of the secondary production ranged from 1,456 to 4,127 gWW/m²/yr, which is more than the secondary production of clams (Ruditapes philippinarum) in Ariake Bay. Furthermore, this data showed a negative correlation between the tide height and the secondary production. Considering the above results, the further discussion and research on this issue with the utmost effort are needed.