Promoting oyster culture in Ghana: Strategies for optimising seed collection and growth of crassostrea tulipa (lamarck, 1819) in coastal water bodies

Abstract

The study explored simple strategies for optimising seed collection and growth of the mangrove oyster Crassostrea tulipa to support its large-scale farming in Ghana. Coconut shell, nylon mesh, recycled oyster shell, PVC slat and ceramic tile were assessed at different depths (top, middle and bottom) and at three different stations each in the Densu Delta, Narkwa Lagoon, Benya Lagoon and Whin Estuary. Ceramic tile, PVC and oyster shell were more efficient spat collectors than coconut shell. Spat settled more profusely on under-horizontal surfaces of collectors compared with the upper surfaces. Spatfall was highest at Narkwa Lagoon, recording 1.3, 2.5, and 9.8 times spatfall in the Densu, Benya and Whin systems respectively. Spatfall was highest in the dry season in Densu Delta and Narkwa Lagoon. In Benya Lagoon it was highest in the wet season but showed no seasonal pattern in Whin Estuary. Spatfall, spat sizes and growth of cultured C. tulipa were significantly greater on middle and bottom collectors than on top collectors. Dissolved oxygen (DO) and salinity were the significant predictors of spatfall whereas those for growth were DO and turbidity. C. tulipa spat stocked at 0.14 spat cm-2 i.e. 1 spat per 7 cm2 produced ‘market-size’ oysters in six months. There was a significant difference in the growth of C. tulipa among the different water bodies with fastest absolute growth rate recorded in Narkwa Lagoon (AGR = 0.33 mm day-1). Fistubalanus pallidus was the most ubiquitous and Ficopomatus sp. was the most deleterious fouling organisms associated with the C. tulipa spat collection and culture. Further studies on genetic variability, nutrient loads and others are recommended in order to fully explain and consolidate the findings of this study.