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

Water Temperature and Cyclone Frequency in the Pacific: Implications for Pearl Farming Final, June 20083.4.2 Impact on the Physical Environment of Key Pacific Island GroupsThe impact of tropical cyclones on the physical environment of Pacific Island groupsdepends on their frequency, intensity, speed of movement, longevity, size and proximity tothe island groups and how the physical features of the affected islands influence theirresponse to the geomorphic and hydrological processes triggered by the cyclone (Terry2007). Low-lying coral islands, such as those on atolls, are the most vulnerable to impacts.These islands consist of unconsolidated heaps of coralline sands and gravel on top of reeffoundations and are prone to overtopping by storm surge and wave action generated bycyclones. On mountainous volcanic islands, characterized by rugged topography andweathered clay soils, heavy cyclonic rainfall can result in landslides on hills and depositionof sediment in valley bottoms. Tropical cyclones usually have less impact on limestoneislands, because these have no significant relief on which slope failures can occur and nosurface drainage channels that can be flooded.3.4.3 Impacts on Pearl Fishing and FarmingIn November 1910, a cyclone, with winds estimated at 175 km/h caused 34 pearling boats tobe wrecked or sunk and a further 67 boats to be blown ashore in the Broome region,northwest Australia (Bureau of Meteorology, Australia 2007c). In March 1935, a cyclonedevastated the pearling fleet at the Lacepede Islands, caused the deaths of 141 people anddemolished pearling camps in Broome. In March 1989, the storm surge accompanyingCyclone Mahina destroyed the pearling fleet and killed 400 people at Bathurst Bay, nearCape Melville, Queensland (Emergency Management, Australia 2003). In Exmouth Gulf,Western Australia, cyclone-induced damage to benthic habitat has led to fluctuations in theavailability of wild stock and reductions in landings by the fishery (Department of Fisheries,Western Australia 2002). The heavy rainfall (395 mm), high winds (with gusts up to 273km/h) and storm surge that accompanied category 5 cyclone Vance in March 1999, causedwidespread movement of pearl oysters and equipment on experimental lines andcommercial oyster farms in Exmouth Gulf (Hart and Joll 2006). In April 2000, CycloneRosita caused wide-scale damage to pearling facilities and the loss of eight boats in thevicinity of Broome. Paspaley pearls estimated that the losses to the Broome pearlingindustry amounted to about A$6 million (Department of Primary Industries, WesternAustralia 2002). Cyclone-induced movements of sand and silt can impact on pearl oysterbanks by smothering brood stock and recruits. In the early stages of this fishery, cyclonesled to loss of human life and boats.Aquaculture installations situated within the cyclone belt may also be subject to episodicdamage by storm surges and strong winds. The reduction in number and total area of pearlfarms in Manihiki Atoll, Cook Islands that occurred between 1997 and 1999 has beenattributed to the impact of Cyclone Martin in 1997 (Ponia et al. 2000). Although damage tounderwater farming operations was limited, this cyclone caused the loss of harvested pearlsand equipment, damage to the above-water infrastructure and villages and loss of 19 lives(Macpherson 2000). Within a two month period in 1983, French Polynesia was hit by fivecyclones; more than in the previous 150 years. The attendant 4-5 m rise in sea level and 8-10m high waves resulted in the total submergence of many villages on the atolls, anddestroyed boats, fishing equipment and pearl aquaculture rafts (UNESCAP 2000).The Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 15