In this paper, we assess the growth performance, survival rate and abiotic factors affecting Etheria elliptica (Mollusca: Bivalvia: Etheriidae), the African freshwater oyster, a species that is widespread in tropical Africa where it is widely harvested for food and as a commodity. We collected wild oysters from the Pendjari River (Benin) and grouped them into small (23.4 ± 5.2 mm) and large (55.8 ± 7.7 mm) size classes. They were reared in cages in the Pendjari River from January to December 2009. Shell height was measured on a monthly basis, and estimated growth parameters were assessed using the von Bertalanffy growth function. Overall, the growth parameter estimates for pooled size classes were K = 0.0718 month−1 and L∞ = 82.2 mm. We estimated the time to reach minimum commercial size T65mm (female sexual maturity size) to be 22 months (1.8 years). Small oysters exhibited a peak in growth rate (2.775 mm month−1) in May, whereas large-sized oysters grew fastest (1.707–2.781 mm month−1) in August–September during the rainy/flood season. Survival of small-sized oysters declined sharply from May (60%) to June (11%) at the onset of the rainy season, six months after the beginning of experiment, while large oysters had higher survival in June (79.2%), which decreased in December (26.4%). Among abiotic factors investigated, water transparency was negatively correlated with the growth increment of small-sized oysters (p < 0.05). E. elliptica is a suitable candidate for culture due to its large maximum size, reasonable growth rate, and wide geographic range.
Auteurs du document :
Giraud David Akélé, Simon Ahouansou Montcho, Philippe Adédjobi Lalèyè