Abstract
Growth, maturation and spawning season of Fulvia mutica (Reeve) were examined using shell length frequency analysis, and seasonal changes in percentages occurrence of the mature individuals.Size-frequency analysis of shell length showed that the mode of 0-age group was less than 20mm in August, and grew over 60mm by next April. Thereafter, however, one year age group showed a very slow growth. It seems that most of the cockle can not survive till age two. The von Bertalanffy growth curve of the cockle was determined as SLt=96.42[1-exp{-0.0818(t-0.2007)}], where SLt is shell length in mm at age t in month.Both the condition factor and meat weight index were high in March and low after June. Percentage occurrence of mature individuals showed a peak from April to July, and decreased sharply afterward. The shell length of the mature individuals were ranged from 50mm to 55mm, which were supposed to be just one year in age. Analysis showed that spawning season of the cockle in Tokyo Bay lasted from April to July with the major spawning period of May and June.
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