Jintamas Suwanjarat, Chinnawat Pituksalee, and Suppattana Thongchai

pp. 471 - 479

Abstract

The reproductive cycle of the blood clam Anadara granosa, obtained from two different areas at Pattani Bay (Rusamilae and Laem-nok), on the eastern coast of southern Thailand was examined histologically between July 2005 and June 2006. The specimens were analyzed to determine the variability in their cycles under different environmental conditions.
Variations of Cd, Cu, Zn, Mn, and Pb concentration in the sediments and clam tissues were measured. Results showed that gametogenesis of A. granosa occurred throughout the year with slightly different spawning periods at the two sites. The gonad index indicated that the sexual maturity of A. granosa at the Rusamilae site was greater than that at the Laem-Nok
site, suggesting that the Rusamilae site is a more suitable location for A. granosa breeding and culture than the Laem-Nok site. The concentration of heavy metals (Cd, Cu, Zn, Mn, and Pb) in the sediments from both sites were not significantly different, except that the sediments from Laem-Nok had a significantly higher Pb level than at Rusamilae. The data showed
correlation between the metal levels in tissue and the reproductive cycle of A. granosa at Laem-Nok. The breeding season of A. granosa in Pattani Bay is mainly from July to August. Thus, for the conservation of A. granosa in this area harvesting should be avoided during this time, and the best time for collecting this clam at Pattani Bay is suggested to be between
February and June which is not the breeding season.