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

Suitability of Habitats for Growth of Black-Lip and Silver-Lip Pearl Oysters Final, June 2008islands and in the open ocean. The growth rate of oysters and mean annual shell growthincrement were significantly greater in island lagoons and the ocean habitat than in atolllagoons. Oysters also attained a size suitable for implantation of a nucleus faster in thewater off high islands and in the open ocean than in the atoll lagoons. Differences in growthrate were attributed to the negative effects of high (≥ 30 °C) water temperatures, differencesin the degree of water renewal and food supply around the oysters. In Australia, the growthrate and survival of medium and large size oysters and condition of medium-sized animalswere significantly smaller in turbid waters adjacent to the mainland than in nearoligotrophic waters further offshore. The poor performance of black-lip pearl oysters underturbid conditions suggests that commercial culture may be less viable in this type ofenvironment.Silver-lip pearl oysters are often cultured in near-shore areas subject to large fluctuations insalinity and high inputs of terrigenous sediment and nutrients during seasonal rainfallevents. The industry is based on adult individuals of a particular size range or hatcheryderivedspat rather than wild spat, hence there is no information on the collection of spat.Reductions in salinity can have an adverse effect on growth rate of spat but not theirsurvival of spat and can also cause detachment of juveniles. There is also evidence fromAustralia that the survival and growth of juveniles is poorer in winter. The timing of theintroduction of hatchery-reared spat consequently requires careful consideration.Information about the environmental conditions prevailing at silver-lip pearl farms is scarce.Experimental studies on the growth, survival and condition of silver-lip pearl oystersundertaken in two dissimilar environments adjacent to the Great Barrier Reef indicate thatthe growth rate and final condition of oysters cultured in the mainland bay was notsignificantly different from that at the offshore location. This implies that silver-lip pearloysters are physiologically adapted to a wide range of food concentrations and that theycould potentially be cultured in a variety of habitats.Overall conclusionsAlthough black-lip and silver-lip pearl oyster farming are lucrative industries, there is asurprising lack of basic information on the influence of environmental factors on theirbiology and ecology and on environmental conditions at existing farms and their influenceon culture practices. Information on coral reef habitats within some of the specified regionsof the Pacific Ocean is also lacking. This lack of information hinders assessments about thesuitability of available habitats for growing pearl oysters in the Solomon Islands relative tothose in the other Pacific regions. Despite this, it is clear from the literature sourced that,from an environmental perspective, there is potential for farming of both black-lip andsilver-lip pearl oysters to take place in the Solomon Islands. The turbid waters adjacent tothe leeward side of the mountainous islands are likely to be more favourable for farmingsilver-lip than black-lip pearl oysters.The Ecology Lab Pty Ltd – Marine and Freshwater StudiesPage iii