Growth Resting Band Marked on the Shell of Cockle.

概要

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Spawning of cockles, <I>Fulvia mutica</I>, occurs in spring and autumn in Miyazu Bay, Kyoto. Based on the observation of cockles released from a hatchery in 1987 and 1988 and recaptured in July 1989, some differences in the growth resting band on shells between two broods were estimated for the width of the band and its position on the shell.<BR>During the first year, any resting bands were not marked for the spring broods, while for the autumn broods, rather wide band (8.3mm) was formed at the middle part of the shell. Cockles of the spring broods caught in July of the second year had the band (4.0mm width) at the edge of theshell. From these findings, cockles commercially caught can be identified as spring and autumn broods, respectively.<BR>In order to estimate the time when the band was formed on shells, relations between band formation and monthly changes of sexual maturation and body weight were investigated. It is probable that the growth resting band for autumn broods was formed when high water temperature and maturation occur simultaneously.
日本水産増殖学会の論文