Growth Curve of Hard Clam Mercenaria mercenaria in the Sanbanze Tidal Flats of Tokyo Bay

Abstract

ABSTRACT : This paper estimated the shell length growth function of hard clam Mercenaria mercenaria in the Sanbanze tidal flats of Tokyo bay. Shell length, shell height, and shell width were measured for samples caught in the Sanbanze tidal flats from September 2015 to December 2017. Stepped shape rings observed on shell surface were employed for the age determination. The marginal growth rate was calculated from the number of stepped shape rings and the shell length of each ring to determine when the ring was formed. The growth trends could not be found from monthly changes in shell length composition. The monthly variation of the marginal growth rate indicated that the stepped shape ring on shell surface was form once a year around January. Accordingly, the number of stepped shape rings was regarded as age. The relation of shell length to age was approximated with the von Bertalanffy's growth function. The asymptotic shell length, growth coefficient and age when the shell length became 0 mm were estimated as 86.1 mm, 0.175 /year and - 0.497, respectively.