Reproductive Cycle of the Edible Oyster <i>Crassostrea belcheri</i> in the Myeik Coastal Area of Southern Myanmar

This study investigated the reproductive cycle of the edible oyster, Crassostrea belcheri, harvested originally from creeks near Pedaing village in the southern part of Myanmar in September 2017-October 2018 through histological analysis. Five maturity stages were detected in the C. belcheri gonads: indifferent, developing, mature, spawning, and spent. The overall sex ratio of males to females of 1:0.98 showed no statistically significant difference from the expected sex ratio of 1:1 in any month. Hermaphrodites could not be observed in 250 oysters. Moreover, the quantitative monthly gonad index values varied from 1.5 in November and June to 2.75 in March. Histological analysis of C. belcheri revealed that mature male and female gonads were detected in almost all months, except in November-December 2017 and June 2018. Spawning occurred throughout the study period, except in January-March 2018, peaking at the beginning and end of the dry season in October-November and April-May, respectively.