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

Figure 5. The two basic types ofcollector compared in the Friedman andBell (1996) study. Twenty of each typewere deployed, half in protective meshbags and half open. The plastic sheetingwas more effective than the shade meshand the bags proved to have noprotective effect.4.3 Seasonal pattern of spatfallFrom June 1997 to October 2003, ten spat collectors were deployed at three sites closeto Gizo and four sites in Noro for two month immersion times, every two months. Onharvesting the collectors the spat were counted and measured. The same collectortype was used throughout, and the same staff were responsible for all practical aspectsof the collection; this makes this an excellent dataset from which to extract seasonalpatterns of settlement.To examine the seasonal pattern of spat settlement we first normalised for theconsistent differences between sites by dividing the catch for each period at each siteby the overall median catch for that site. The normalised catch from all of the sevensites were combined and plotted against month as a single plot (Figure 6). A timecatchrelationship was then determined by least-squares regression analysis. The bestfit to the data was obtained with a sine function;Catch = 1.8 + 1.34·sin(2·π· (Month)/12+7.9)…………..(equation 1)8