The Effect of Salinity on Particle Filtration Rates of the West African Mangrove Oyster
Previous studies exploring the potential of developing mangrove oyster fisheries in Ghana have suggested that this approach could provide both financial gain (Obodai and Yankson, 1999a) and nutritional value (Yankson 2004) to the Ghanaian people, supplementing a historically low-protein diet as well as augmenting local economies. However ,information on the basic ecology of the West African mangrove oyster (Crassostrea tulipa) is limited. This study aimed to build preliminary knowledge of this species by investigating the precise relationship between environmental salinity and filtration rates. The oyster is a euryhaline organism that thrives in the coastal lagoons of the Ghanaian shoreline. Oysters gathered from two types of coastal lagoons (closed and open) were exposed to salinities varying from 0‰ to 35‰ in intervals of ~7‰ ; filtration rates at each salinity level were measured hourly. The results showed that a significant difference (p<0.001) did exist between the filtration rates of oysters collected from the two sites: the ones collected from the closed lagoon had a greater mean filtration rate at all salinity levels in comparison with those from the open lagoon (6.567 ppm/min, closed lagoon; 3.485 ppm/min, open lagoon).This may be due to either an environmental adaptation or a genetic variation promoting increased filtration capacity, and subsequently, could indicate the presence of two distinct subspecies of C. tulipa. Regardless , the higher filtration capacity of the closed lagoon population could indicate greater resistance and superior suitability for industrial cultivation in Ghana, and future fishery development work should focus on the in situ husbandry of this closed lagoon subtype .