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

Suitability of Habitats for Growth of Black-Lip and Silver-Lip Pearl Oysters Final, June 20082.0 ENVIRONMENTAL NEEDS OF PEARL OYSTERS2.1 IntroductionThe environmental factors that are likely to have the greatest influence on the biology andecology of pearl oysters are temperature, salinity, type of substratum, depth of the water, siltload, water currents, primary productivity and pollution (Gervis and Sims 1992). Althoughsuch factors are known to have significant effects on the physiology, survival andproductivity of bivalves (Jorgensen 1990; Gosling 2003) there have been relatively fewstudies on the responses of black-lip and silver-lip pearl oysters to fluctuations inenvironmental factors. The combined effects of temperature and salinity on embryos andlarvae of black-lip oysters from the Great Barrier Reef and effects of salinity on growth andsurvival of silver-lip spat have been documented by Dourodi et al. (1999) and Taylor et al.(2004), respectively. The influence of salinity on detachment of silver-lip spat has also beendescribed (Taylor et al. 1997). The effects of temperature and suspended particulate matter(SPM) on feeding of black-lip and silver-lip oysters from the Great Barrier Reef (GBR),Australia has been investigated by Yukihira et al. (1999, 2000). The influence of foodavailability on black-lip oysters in French Polynesia has also been investigated (Pouvreau etal. 1999a and b, 2000a and b; Loret et al. 2000a and b). When reading this overview, it isimportant to bear in mind that black-lip and silver-lip pearl oysters growing in other regionsmay exhibit different responses to those reported here and that responses of larvae, juvenilesand adults to environmental factors are likely to differ.The information that is currently available on the influence of each environmental factor issummarised below.2.2 Geographic DistributionBlack-lip pearl oysters are found in the Persian Gulf, Red Sea, Sudan, Papua New Guinea,Australia, French Polynesia, Indonesia, Andaman and Nicobar Islands, southwestern part ofthe Indian Ocean, Japan and the Pacific Ocean. This species reaches its greatest abundancein the atoll lagoons of French Polynesia and the Cook Islands (Gervis and Sims 1992).Silver-lip pearl oysters are distributed along the north coast of Australia, Burma, Thailand,Indonesia, Philippines and Papua New Guinea at depths ranging from low tide level to 80 m(Bueno et al. 1991; Gervis and Sims 1992).2.3 TemperatureTemperature determines the rate of deposition of nacre on shells and nuclei and thereforelimits pearl culture sites to areas within the optimum temperature range (Gervis and Sims1992). Relatively little information, however, is available about the optimal temperatureranges of black-lip and silver-lip pearl oysters. It should also be noted that most of thestudies on the effects of temperature on black-lip and silver-lip pearl oysters were done inwaters off the Great Barrier Reef (GBR) on the north-east coast of Australia. It is thereforenot known whether the ranges reported below are applicable throughout the species’geographic ranges.Doroudi et al. (1999) reported that normal development of black-lip oyster embryos occurredonly between 25 °C and 30 °C, that growth of larvae was optimal between 26 °C and 29 °CThe Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 3