Annual gametogenic development of the Asiatic hard clam, Meretrix meretrix, collected from the west coast of Moheshkhali Island, Cox's Bazar, Bangladesh

Abstract

We investigated the annual gametogenic development of the Asiatic hard clam, Meretrix meretrix, collected from the west coast of Moheshkhali Island, Cox's Bazar, Bangladesh, by using biometry and histology through monthly sampling from July 2018 to June 2019. After biometric measurements, cross sections were cut for histology to determine the sex and gonadal maturity of the clams. Condition index (CI) showed two distinct peaks in July and December, which indicated that clams were ripe during these months, and a subsequent decrease in CI reflected spawning, which was consistent with histology. Our study revealed a biannual spawning cycle of the clams and gametogenesis starting in October and June. Spawning occurred from February to May and July to September. Maturity index (MI) showed two distinct peaks in July (3.50) and January (3.60) when most of the clams were in late developing or ripe stages. A gradual increase in temperature from annual minima in conjunction with decreasing salinity levels may trigger spawning in February, but spawning in July was initiated when salinity levels increased from annual minima. The data could be used by resource managers for the conservation of this commercial species and to time harvesting for the best quality clams without interrupting spawning activity.