A collaborative investigation of options for spat collection and hatchery production of pearl oysters in the central-western Pacific

• Ministry of Agriculture and Fisheries, Solomon Islands
• James Cook University, Australia

The broad objectives of this grant were to test the availability of pearl oyster spat in Solomon Islands waters using a variety of spat collectors, and to determine whether spat can be produced in hatcheries using techniques suitable for developing village-based farming systems.

1) Two sites in the Western Province appear to have potential to act as areas where spat can be caught in sufficient quantities to establish low-technology, village farms for pearl oysters.
2) In the Solomon Islands, spat of blacklip Pearl oyster were most abundant on collectors deployed in October and January. However, by the time spat were removed from collectors at a maximum age of 6 months, an average of 43% were dead.
3) Methods for collecting spat were refined. It was found that collectors made from shademesh rather than black plastic attracted at least three times as many spat of blacklip pearl oysters and reduced the cost of collectors by halving the amount of material required.
4) Protective mesh bags used around collectors did not improve harvest of spat by protecting them from predators. On the contrary, they became fouled heavily and trapped predatory gastropods(Cymatium) and crabs which grew and caused heavy mortality of juvenile oysters.
5) Survival of all juveniles placed in lantern nets for grow-out in villages, and in grow-out experiments, totalled only 38%. The mortality was due to predation by Cymatium, crabs and fish, but also inadequate husbandry by village growers.
6) Attempts at rearing the larvae were also only marginally successful and indicated that considerable progress needs to be made before the production of spat in hatcheries can be made economically viable for village-based pearl oyster farmers.

The final technical and financial reports were received in February 1996.