Shell growth of the sand snail, Umbonium costatum (Kiener) in Hakodate bay [Japan]
1991
Noda, T. (Hokkaido Univ., Hakodate (Japan). Faculty of Fisheries)
Shell growth of the sand snail, Umbonium costatum in Hakodate Bay, Hokkaido was studied during the period October 1982 to November 1988. The age of each sand snail was determined by counting the number of shell rings. Recruitment season was also studied from July to September 1987 and from June to September 1988 to determine the initial month of the 0 age group. In 1987 newly recruited juveniles appeared in August and in 1988 they appeared from July to September but were most abundant in August. This indicates that the 0 age group begins in August. The equation representing seasonal growth was obtained following Pauly and Gaschutz's modified Bertalanffy equation; Lt=22.024(1-exp(-0.793(t/12-0.050)+0.150(sin(2pi(t/12-0.421) ))), where Lt=shell diameter (mm) and t=age in months. Seasonality of shell growth in this species is strongly affected by temperature. However, various other factors could also have considerably affected shell growth because shell growth from April to July was much greater compared to the period October to January in the same temperature condition
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