The Status of Silverlip Pearl OysterPinctada maxima(Jameson) (Mollusca, Pteridae) in the Solomon Islands After A 15-Year Export Ban

Abstract

In the Solomon Islands, there have been three periods of commercial exploitation of the silver (gold)-lip pearl oyster Pinctada maxima. The most recent ended in 1993, when export of all species of pearl oysters was banned to allow stocks to recover from overexploitation. In 2007, a nationwide survey was undertaken to determine the status of the population. Communities adjacent to former fishing grounds were interviewed about past and current fishing practices, and the abundance, size composition, and quality of P. maxima shells were assessed by drift diving. In total, 117 P. maxima were recorded, from 33 of 96 transects. When present, the mean density of oysters varied from less than 0.10-1.23 oysters/400-m 2 transect. Size structure was biased toward large individuals, with mean and median shell size for all oysters taken being 219 mm. There appears to have been little or no recovery of P. maxima stocks since their export was banned. The existence of small populations of large individuals implies persistent failure of reproduction, spat settlement, and/or recruitment during the past decade. Exploitation may have reduced the P. maxima populations to such an extent that their fertilization success has become susceptible to Allee effects. Recent poaching of shell reported by local villagers may have compounded slow or sporadic recruitment. If the stocks do eventually recover, management strategies that protect the recovered population will need to be implemented to prevent a repeat of the overfishing seen in previous harvest cycles.