Reproductive cycle of the Crassostrea gasar oyster in Grand-Lahou lagoon (Côte d’Ivoire)

The mangrove oyster Crassostrea gasar is an important fishery resource and a valuable source of animal protein and income for local communities in Côte d'Ivoire.Despite its socio-economic importance, information on its reproductive biology in the Grand-Lahou lagoon remains limited.This study aimed to characterize the reproductive cycle and sex structure of C. gasar in the Grand-Lahou lagoon.Monthly samples of 30 oysters (>4 cm shell length) were collected from natural oyster beds between February 2019 and January 2020, yielding a total of 360 individuals.Gonadal tissues were processed using standard histological techniques and stained with hematoxylin and eosin for microscopic examination.Sexual maturity stages were identified according to gonadal development, and seasonal variations in sex ratio and maturity-stage distribution were assessed using the G-test at a significance level of p ≤ 0.05.Histological observations revealed five gonadal maturity stages in both males and females: resting, early development, developing, ripe, and spawning.Three categories of individuals were identified: females (48.47%), males (34.58%), and undifferentiated individuals (16.94%).The overall sex ratio was significantly biased toward females, with an average ratio of 1 male to 1.5 females (p < 0.001).Female