MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14818

ABSTRACT: Year-to-year fluctuations in the densities of bivalve populations are often large. This hinders short-time forecasting and control of their densities. Such hindrances would be mitigated by elucidating (1) the life stage and (2) the environmental factors that strongly affect the year-to-year density fluctuation. These were examined for the asari clam Ruditapes philippinarum on an intertidal sandflat near the mouth of the Midori River, western Japan, from 1992 to 2015. Analyses of the densities of juvenile (≈0–2 mm in shell length), subadult (≈5–15 mm) and adult (20–30 mm) collected twice a year and environmental data (sand grain size, air temperature, salinity, discharge of the Midori River, and wind speed as an indicator of wave height) revealed the following results. (1) The fluctuation in adult density during one year (year_j) to the following year (year_j+1) was mainly explained by the fluctuation in subadult/juvenile density ratio during the previous years (year_j-1 to year_j). (2) This fluctuation in subadult/juvenile density ratio showed a significant negative correlation with the fluctuation in the wind speed during the same period (year_j-1 to year_j). With the fluctuation in wind speed increasing, the fluctuation in the disturbance of spatial distribution patterns for juveniles and subadults also increased. These results indicate that increased wind speed leads to increased disturbance of the sandflat and decreased juvenile-subadult survival rate, which in turn leads to a decreased adult density.