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

Water Temperature and Cyclone Frequency in the Pacific: Implications for Pearl Farming Final, June 2008temperature records for silver-lip pearl oyster farms in Western Australia ranged from ca 19– 30 °C, 21 – 31 °C and 25 – 32 °C. This implies that black pearl farms are either located inareas where the water temperature is outside the optimum temperature range or that theoptimum ranges of this species in other countries differs markedly from that in north-eastAustralia. Some of the Western Australian silver-lip pearl farms are located in areas wherethe minimum water temperature is below the lower limit of the optimum temperature rangeor where the maximum water temperature is close to the upper limit of the optimum range.If global warming causes a 0.4-1.0º C increase in the sea temperature off the north-west coastof Australia as is predicted, temperatures at some farm locations could exceed the optimaltemperature range of silver-lip oysters.Temperature probes have also been deployed at several other locations in northern Australiaand Fiji and from one location in Papua New Guinea. The long-term data set obtained froma probe deployed at one particular location in Fiji indicates that there is considerable interannualvariability in SST. This suggests that time series data would probably be more usefulthan average monthly SST estimates, for gauging prevailing temperature regimes.The sea-level fine resolution acoustic measuring (SEAFRAME) gauges installed at singlelocations in the Cook Islands, Fiji, Papua New Guinea, Solomon Islands and Vanuatu in theearly 1990s provide contemporaneous records of SST. These indicate that the temperaturerange off Papua New Guinea (4.8 °C) and the Solomon Islands (5.4 °C) is narrower than thatoff the Cook Islands, Fiji and Vanuatu (8.2-8.5 °C). The records also show that mean watertemperatures off Papua New Guinea and the Solomon Islands were about 2° C cooler thannormal during the 1997/1998 El Niño event.SST measurements derived from sensors carried on board polar-orbiting satellites were alsoexamined. Comparable SST data for locations in the regions of interest were obtained fromthe Modern Average Global SST Dataset produced by the US Geological Survey. These datawere derived from weekly measurements taken by an Advanced Very High ResolutionRadiometer sensor over the period October 1981 to December 1990. More recent monthlySST climatology data were obtained for locations around Australia by using the surfacetemperature search tool maintained by the Australian Department of Defence. Time seriesdata for five locations on the north-east coast of Australia were obtained from the SST webatlas for the Great Barrier Reef region produced by the Australian Institute of Marine Scienceand CRC Reef Research Centre. Time series for five locations in Australia and two locationsin the South Pacific were also obtained from the National Oceanic and AtmosphericAdministration’s Coral Reef Watch Program.The limited information that is available on sea temperatures in Solomon Islands indicatesthat the prevailing regimes are similar to those in some areas of the Cook Islands and FrenchPolynesia, where there are productive black-lip pearl farms. Similar temperature regimesalso prevail in some areas of Vanuatu, Fiji and Papua New Guinea. The fact that thetemperature of the water at locations in the Solomon Islands and Papua New Guinearegularly exceeds 29 °C in summer, however, implies that these regions may be moresuitable for culturing silver-lip than black-lip pearl oysters. The temperature regimes atmost of the locations in Fiji and Vanuatu, in contrast, appear to be suitable for culturing bothspecies of pearl oysters, but silver-lip pearl oysters do not occur naturally in these waters.On the basis of our current knowledge, it is not possible to say whether the sea temperatureregime in Solomon Islands would be more advantageous for pearl farming than that in theother South Pacific nations considered.The Ecology Lab Pty Ltd – Marine and Freshwater StudiesPage ii