Stimulating investment in pearl farming in ... - World Fish Center

Abundance, Size Structure and Quality of Silver-lip Pearl Oysters in the Solomon Islands Final, June 2008overgrown by other biota. The maximum average number of “possible” live oysters foundper transect was one, suggesting that these animals are also scarce at depths of 35-50m.The low densities of silver-lip oysters observed in the underwater and remote visualcensuses suggest that stocks have not recovered to sustainable levels since fishing wasprohibited in 1994. The lack of small animals suggests that recruitment may haveconsistently failed during this period.As pearl oysters change from male to female as they age, most of the oysters found duringthe current and previous surveys undertaken in the Solomon Islands are likely to have beenfemale. The current assumed bias in the sex ratio may be partly responsible for a reductionin reproductive output and resulted in impaired, if not total recruitment failure.If historical over-exploitation has led to poor recruitment, recovery of the populations islikely to remain either be very slow or non-existent. It should be noted that some of theblack-lip pearl oyster stocks in the Cook Islands and French Polynesia, subjected to intensefishing during the late nineteenth and early twentieth centuries, had not recovered fromover-exploitation by the 1980s. The fact that stocks in the Waghina region of the SolomonIslands have been subjected to three phases of exploitation suggests that some degree ofrecovery of fished stocks has occurred in the past. An alternative explanation for thisphasing is that changes in fishing method over that period have enabled divers to accessstocks in progressively deeper water.In conclusion, exploitation of silver-lip pearl oysters for pearl culture is not an ecologicallyor commercially viable option at present, because of the paucity of the stocks andunfavourable size of the majority of oysters. If the silver-lip pearl oyster stocks in theSolomon Islands do eventually recover from the last phase of commercial exploitation,management strategies that protect the recovered population will need to be implemented toprevent overfishing prior to any further exploitation.The Ecology Lab Pty Ltd – Marine and Freshwater StudiesPage ii