Permalink : http://hdl.handle.net/2115/56736

KEYWORDS : Short-necked clam;Hakodate Bay;Shell growth;Growth ring;Growth equation;Chlorophyll a;Sediment;Age determination

Shell growth of the short-necked clam Ruditapes philippinarum at Hakodate Bay, Hokkaido, Japan, was studied from February 2011 to February 2012.　Monthly measurements of shell growth increment from the last ring on the shells revealed that a ring was formed annually from February to March.　The Gompertz growth equation was fitted to the relationship between number of rings and shell length, and the equation, LR = 38.41exp (－exp (－0.892 (R－2.029))) was obtained, where LR is the shell length (mm) at the number of ring R.　This equation shows highly depressed growth rate after 30 mm in shell length, and maximum shell length was attained about 40 mm that is smaller than those of the other localities.　The estimated growth pattern was in accordance with the results of analyses of the size frequency distributions.　The observed depressed growth was not explained by a shortage of food supply or seawater temperatures, but may be due to sediment character of including many cobbles and pebbles with sand which disturbs shell growth of the short-necked clam.