A Study on the Fishery, Aspects of the Biology and Culture of the West African Mangrove Oyster, Crassostrea Tulipa in the Densu Delta, Ghana

Abstract

The study investigated the oyster fishery, aspects of the biology and the culture of Crassostrea fulipa in the Densu Delta, Ghana, from May 2017 to October 2018. Almost all the oyster fisherfolk sampled were females, mainly between the ages of 35 to 44 years, with many dependants. The annual catch was estimated to be 295 tonnes, with an appraised value of USD 65,559. The total annual cost of fishing, gross annual income and total annual profit were estimated at USD 11,897, USD 39,993 and USD 28,097, respectively. Generally, the oysters exhibited negative allometry. Oysters in the shallow waters (0.61 m depth) were depleted within six months, but the deep water (2.13m depth) oysters were underexploited. Generally, the monthly sex ratios of the oysters did not deviate from unity. Unlike the deep water oysters. those from the shallow beds exhibited conti nuclis spawning. None of the Physico-chemical parameters predicted breeding. However, oyster condition index was significantly influenced by salinity. pH and phosphate concentrations. Growth and survival of oysters were better when cultured in suspension than at the bottom. Biofouling had no deleterious effect on the growth and survival of oysters cultured on coconut-shell and oyster-shell cultches. Proximate analysis revealed that cultured oysters had a significantly higher composition of carbohydrate and moisture than in wild oysters, while protein, lipids, ash and fibre were comparable in both treatments. Oyster consumers preferred the taste of cultured oyster meat to wild oyster meat. Regulation of the fishery. large-scale cultivation and value· addition is recommended to create jobs, maximise income and to meet both local and international demands.