Biometric Characteristics and Condition Index of the Mangrove Oyster Crassostrea tulipa Lamarck, 1819 in the Interface Ecosystems of the Saloum Delta in Senegal: Case of the Commune of Dionewar

Abstract

The mangrove oyster Crassostrea tulipa (syn. Crassostrea gasar) has been subjected to strong anthropic pressure. As in several West African countries, Senegal in particular in the Saloum delta, the oyster resource was severely strained. This situation had led to disturbances in the renewal of stocks and their productivity. The objective of this study was to determine the size frequency distribution, the size-weight relationship and the condition index in order to provide scientific arguments for sustainable management of C. tulipa. Monthly sampling from January 2021 to January 2022 at the Akat, Baobab Rasta, Falia 1, Falia 2 and Fandiongue stations revealed that the individual sizes of the oysters collected ranged from 0.63 mm to 93.19 mm, with an average height of 34.63 ± 16.12 mm. The size frequency distribution is unimodal with a modal class of 30 - 40 mm and the allometry coefficient is minorizing (2.57). The correlation coefficient is 0.86. However, from one site to another the differences are not significant. The monthly monitoring of the oyster condition index showed several variations in values throughout the year, with an overall average of 11.47±2.89% for the 5 stations. The maximum value (12.97±2.60) was observed in March while the minimum value (9.85±2.22) was recorded in November. This study suggests that C. tulipa is overexploited in the commune of Dionewar and that the best time to collect the oyster is around March.