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

Page 7Other Pacific Island countries produce black-lip pearls in very small quantities. A handful offarms in Fiji and Papua New Guinea have been discreetly run by private operators over thepast 3-4 decades, of which one is currently operating in Fiji. Small donor-funded pilot farmshave operated in Marshall Islands, Federated States of Micronesia, and Kiribati. Tonga hasbeen carrying out research on the winged pearl oyster Pteria penguin with the intention ofeventually establishing a half-pearl industry. Other than Fiji, none of these countries arelikely to be significant pearl producers in the near future. Solomon Islands has also producedblack pearls at a demonstration farm (see report by Hawes and Mesia, 2007, in this series) butto date has also not been commercialised.3.2. Farming operationsBlack-lip pearl farming is typically carried out as follows. Larval pearl oysters are collectedfrom the wild by deploying strings of collectors on long (100-200m) anchored horizontalmainlines (longlines) suspended by floats a few metres below the sea surface. Juvenile pearloysters settling on the collectors are referred to as spat. Collectors are cheap and simple toconstruct, deploy and maintain; originally they were made from twisted up pieces of plasticsheeting, onion bags or bundles of twigs; nowadays they are often made of ‘mussel-rope’, aspecial rope manufactured specially for shellfish spat collection, which has its strandsdeliberately frayed or left hanging from the standing part of the rope.A typical small-scale collection operation might involve a few hundred individual spatcollectors strung along half-a-dozen mainlines. Each individual collector may collect a fewspat or a few hundred, depending on the characteristics of the collection area. Spat areallowed to grow to the size where they can be properly handled (at a minimum, about the sizeof a thumbnail, but usually somewhat larger) and then may be transferred to grow out lines orcages, or simply left to grow on the collector. Different areas have different characteristics inregard to mortality, predation, fouling by other organisms, etc., and this determines to a largedegree how early the spat need to be transferred and the handling practices to be followed.Spat collection and grow-out require little specialised equipment or knowledge and can beaccomplished by semi-skilled and unskilled operators.When the juveniles are about 15 cm in dorso-ventral measurement they can be prepared forimplantation with an artificial pearl nucleus. The preparation process involves deliberatelystressing the shell for several days or weeks before surgery, in order to clear reproductiveproducts from the gonads and make implantation easier. This is often done by dropping thepre-op shell lines to lie in a heap on the seafloor to deprive them of food and oxygen.Weakening the shell in this way reduces its ability to reject the nucleus after surgery,although there is a risk that the shell will be weakened so much that it will not survivesurgery at all. After mortality and rejection, a nucleus retention rate of 70% in the implantedshell would be considered good. Research carried out in Australia in the 1990s concluded thatbetter survival and retention rates could be achieved by anaesthetising the shell prior tosurgery, rather than stressing them, but anaesthesia is still an uncommon practice in theindustry.Carrying out the implantation operation is a highly skilled profession practiced byexperienced seeding technicians. It is a surgical operation in which the shell is partiallyopened, an incision made in the gonad, and a bead ground from the shell of a particularspecies of freshwater bivalve inserted. On top of the bead is placed a portion of mantle tissuefrom another pearl oyster, which has been sacrificed for this purpose. The operated oyster isthen returned to the farm where it is hoped that the incision will heal, the inserted piece ofmantle will form a pearl sac around the bead, and this will then deposit mother-of-pearl on