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

Abundance, Size Structure and Quality of Silver-lip Pearl Oysters in the Solomon Islands Final, June 2008In 1993, ICLARM and the Solomon Islands Fisheries Division surveyed the abundance ofblack-lip pearl oysters around population centres on Guadalcanal, Malaita, Florida Islands,Russell Islands, New Georgia and Gizo and interviewed local villagers about the status ofthe stocks (Richards et al. 1994). The maximum abundance observed was 12 oysters perdiver hour, but most encounter rates were in the order of 2-3 oysters per diver hour. Theinterviewees claimed that oyster stocks had declined considerably over the previous tenyears.In June 2004, The Nature Conservancy and Department of Fisheries and Marine Resourcesof the Solomon Islands Government conducted a “broad-brush” assessment of commerciallyimportant species, including pearl oysters, in the main archipelago. Sixty-six sites,stretching from Choiseul and Shortland Islands in the northwest to the Three Sisters and SanCristobal in the southeast, were surveyed over a 6 day period. Thirty-five sites were locatedin coral reef habitats on parts of islands exposed to direct wind and wave action. The othersites were generally in sheltered lagoons and bays. At most sites, both shallow (5-10 mdeep) and deep (18-30 m) habitats were surveyed. In the shallow habitat, six 50 m long x 2m wide transects laid over the terrace or slope in shallow habitats were surveyed per site. Inthe deep habitat, five 50 m long x 5 m wide transects laid parallel to the reef crest and oversoft sediments or rubble were surveyed per site.Black-lip (Pinctada margaritifera) and brown-lip (Pteria penguin) pearl oysters were collectedin shallow and deep habitats and at sheltered and exposed locations, but no silver-lip pearloysters were found. Black-lip pearl oysters were found in 36.4% of the shallow habitats and4.8% of the deep habitats surveyed, whereas brown-lip pearl oysters were found in only6.1% of the shallow habitats and 12.7% of the deep habitats surveyed. In the shallow habitat,similar total numbers of black-lip (39) and brown-lip (41) pearl oysters were found.However, in the deep habitat, brown-lip pearl oysters (40) were an order of magnitude moreabundant than black-lip oysters (4). Black-lip oysters were equally abundant in shelteredand exposed locations, but brown-lip oysters were more abundant in sheltered locations.The respective average densities (no./ha) of black lip and brown-lip oysters was 9 and 11 inshallow habitats and 0.4 and 4 in deep habitats. In the shallow habitat, the mean number ofblack-lip oysters per transect was two-three times greater in Mbili Passage in MarovoLagoon (Western Province), Falabulu Island in Langalanga Lagoon (Malaita) and Gavutu inNgella (between Malaita and Guadalcanal) than at the other sites. Most of the black-lipoysters found in this habitat were large animals, with a DVM > 12 cm. The greatest densityof brown-lip oysters was found at Airasia in Are’ Are Lagoon.The Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 4