Spatial and Seasonal Variations in the Size-Weight Relationship and Condition Index of the Mangrove Oyster Crassostrea tulipa (Lamarck, 1819) in the Saloum Delta, Senegal

Abstract

In the Saloum delta in Senegal, the mangrove oyster Crassostrea tulipa is under increasing human pressure, leading to a decline in wild stocks, a decrease in the quality of the marketed oysters and the degradation of mangrove tree roots. Previous studies have pinpointed some of these disturbances and yet, there is little information available on the structure of the population and the condition index of the species. The aim of this study was to document these aspects in order to support a sustainable management of the resource. From January 2021 to December 2022, monthly sampling was carried out at five stations to study the size-weight relationship and the condition index (CI) of oysters. A total of 26,790 individuals ranging in size from 0.23 to 93.19 mm with an average of 33.86±16.38 mm shell height were collected. The species was found to have a minority allometry (b = 2.54 <3), with a strong correlation between individual weight and oyster shell height (r = 0.88). CI showed seasonal and inter-site variations over the two years, with an overall mean value of 11.17±2.72%. The highest CI values were observed during the hot season and the lowest during the hot-cold transition period.