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

The third attempt at spawning yielded approximately 2000 spat, which weretransferred to the Nusa Tupe research centre for experimental grow-out. Furtherexperiments in hatchery culture were terminated when the Aruligo site was damagedduring the ethnic tensions of 2000.5. Spat grow-out5.1 Development of intermediate cultureThe high mortality of spat on collectors in Solomon Island waters means that thelonger the spat collectors are deployed (after 3-4 months) the fewer spat are returned.Not only this, but there is little to be gained in terms of increase in average spat sizefrom prolonged immersion of spat collectors. Thus the strategy used in many pearlfarming locations of leaving spat on collectors until they are ready to be hung on linesmay be inappropriate. Friedman and Bell (2000) found that mortality was 42% forspat left on collectors between month four and month six. This is higher than the 30%rate reported by Coeroli et al. (1984) for 6-12 month old juveniles in FrenchPolynesian lagoons. An experimental intermediate grow-out system has beendeveloped for Solomon Islands that takes spat from collectors at a small size andgrows them out in trays until they reach a size large enough to be strung.The benefit of intermediate growth is the increase in spat survival. Compared with the58% survival of spat left on collectors, spat larger than 15 mm survived at 82-93%when they were removed and transferred to protective cages (panel nets; Friedmanand Bell, 2000). For very small spat (