Wild Black-lip Pearl Oyster ( Pinctada margaritifera ) Spat Collection in Tanzania

Abstract

Pearl farming is a growing aquaculture activity in Tanzania but requires sufficient young pearl oysters to make it feasible. Collection of spat in the wild is the most viable way of doing this and was tested to establish whether it would yield sufficient juvenile pearl oysters to support an industry. A total of 4263 Pinctada margaritifera spat were collected over a year at sites considered suitable for spat collection: Bweleo and Nyamanzi on Zanzibar, and Tawalani in Northern Tanzania. Spat "yield" exhibited seasonal variations at these sites in a pattern similar in annual trend at Tawalani and Bweleo but different at Nyamanzi. Generally, the dry season (June-November) yielded a higher number of spat than the wet season (December-May). During the dry season, Tawalani, Bweleo and Nyamanzi produced 877, 942 and 1176 P. margaritifera spat respectively, while, during the wet season, these numbers were 503, 730 and 35. A few other pearl oysters such as Pteria penguin were inadvertently collected at Nyamanzi during the study. Three different types of spat collectors were used during the study, comprising coconut shells, spat bags and rubber tiles. There was significant variation in the number of spat collected on these materials (P < 0.01). The yield was always greater on spat bags and rubber tiles than on coconut shells. The study showed that it is possible to collect sufficient numbers of wild spat for the culture of black-lip pearl oysters at some sites along the coast of Tanzania.