Growth of freshwater Etheria elliptica oyster (Lamarck, 1807) reared in cages in the Pendjari River (Benin, West Africa)

Abstract

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 À1 and L ∞ = 82.2 mm. We estimated the time to reach minimum commercial size T 65mm (female sexual maturity size) to be 22 months (1.8 years). Small oysters exhibited a peak in growth rate (2.775 mm month À1) in May, whereas large-sized oysters grew fastest (1.707-2.781 mm month À1) 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.

Survival and growth of mangrove oyster Crassostrea gasar (Dautzenberg, 1891) reared at different depths in ponds in Benin (West Africa)

“…Poor handling during control fisheries is another cause of the mortalities recorded in the present study [16] . The study of oyster growth consisted of taking total weight and shell length measurements of the oysters at each control fishing.…”

Freshwater bivalve shells as hydrologic archives in the Congo Basin

“…E. elliptica grows in moving and often turbulent water, 2-3 m below the surface (Yonge, 1962). Indeed, this species thrives in fast moving water habitat; Akélé et al (2017) reported that growth rates of adult E. elliptica are the highest during rainy/flood period. E. elliptica is intolerant of salinity and desiccation (Van Damme, 1984), juvenile specimens are especially sen-sitive to siltation (Anthony, 1907) and reach sexual maturity (~65 mm) in about 22 months (Akélé et al, 2017).…”

“…Indeed, this species thrives in fast moving water habitat; Akélé et al (2017) reported that growth rates of adult E. elliptica are the highest during rainy/flood period. E. elliptica is intolerant of salinity and desiccation (Van Damme, 1984), juvenile specimens are especially sen-sitive to siltation (Anthony, 1907) and reach sexual maturity (~65 mm) in about 22 months (Akélé et al, 2017). This species lives cemented to a hard substrate, which makes it more sensitive to changes in the aquatic environment than other species, which are able to relocate or bury into a soft substrate.…”

Identification and validation of Western African freshwater Key Biodiversity Areas

“…In recent years, experimental studies have been carried out on cage raising the freshwater oyster, Etheria elliptica, in Benin (Akélé, Montcho & Lalèyè, 2017) as well as growing Aspatharia spp. in Egypt (Goda et al, 2015).…”