N: Number of clams analyzed (table 12, 13). Gonada stage: Percentage (%N) of male or female clams in each of the following gonad stages: early mature; advanced maturity; mature; early regresion; final regresion. Classification was made after histological examination of Bouin-preserved gonad samples. Tissue embedded in paraplast wax after dehydration, sectioned at 7 µm and stained with haematoxylin eosin stain before examination. Data from Table 14 and 16.