Abstract:
This study carried out a comparative assessment of the shellfish fishery in six water
bodies; three in Ghana (Densu, Narkwa and Whin) and three in The Gambia
(Allahein, Bullock and Tanbi). It assessed the ecological, growth and mortality
parameters of Crassostrea tulipa in these waterbodies for 12 months from March
2021 to March 2022. Findings revealed that, the water bodies in The Gambia were
generally deeper, less turbid and with better salinity ranges that enhanced the
survival of the oysters than the Ghanaian waterbodies. This contributed to better
condition indices and bigger sized oysters at the sites in The Gambia. Crassostrea
tulipa at all the six sites significantly deviated from isometric growth. They were
short-lived species with higher growth rate (K/yr) values and higher natural
mortality (M/yr) values. Z/K ratios showed that the populations were mortality
induced (natural mortality) although Bullock and Narkwa showed fishing induced
mortality. The Ecurrent at these two sites also showed an overfished population.
Lc50/L∞ ratio suggested growth overfishing in Ghana while those in The Gambia
were of appropriate sizes. All the populations significantly deviated from a 1:1 sex
ratio except Allahein in The Gambia and Densu in Ghana. The estimated maturity
size indicated that the species in both countries all attained maturity before they
were harvested except Densu in Ghana. All the harvesting sites in The Gambia were
running some form of co-management structure in conjunction with the Gambian
government where restrictions such as seasonal closures, size restrictions, were in
place. In Ghana, Densu also has co-management modalities led mainly by the
women shellfishers and supported by the Government, Densu and Tanbi have co management plans and have been granted exclusive use rights. The fishers in these
jurisdictions were better off in income than oyster fishers in Ghana.
