Is there a case to reduce the duration of spat collector deployment for black-lip (Pinctada margaritifera) and winged (Pteria penguin) pearl oysters in the Fiji Islands?

Abstract

Spat collection activities, targeting black-lip (Pinctada margaritifera) and winged (Pteria penguin) pearl oysters, support successful cultured round pearl and mabé pearl sectors in the Fiji Islands. To improve supply of pearl oysters for pearl production, a national spat collection program was developed based on standardised methodology, where commercially available spat collectors are deployed for 10–18 months. Research is now required to maximise the productivity of this program and optimising the duration of spat collector deployments is seen as a priority. This study considered whether there is justification to reduce the duration of spat collector deployments for black-lip and winged pearl oysters to less than 8 months. Spat collectors were deployed at multiple sites and then recovered after 5, 6, 7, or 8 months to examine the yield and size of resulting spat. While duration of spat collector deployment was important in determining the yield and size of harvested spat, it was not possible to generalise responses. Rather, conclusions were liable to vary over macro and micro spatial scales, depending on the target species. Such variability, coupled with the small size of spat at harvest, greatly limited the feasibility and rationale for reducing the duration of spat collector deployment to improve the supply of pearl oysters for pearl production. On this basis, we argue that there is no justification to modify the standardised methodology currently used within the national spat collection program in Fiji, where spat collectors are deployed for longer than 8 months.