54 SEPTEMBER 2013 • WORLD AQUACULTURE • WWW.WAS.ORG Effect of Planting Density Because oyster growth rates and yield are a function of seeding density and local currents, one useful output of ShellGIS is the comparison, over a large area, of oyster growth rates over a range of bottom planting density. In Figure 5a, oysters planted at 100/m2 grow uniformly throughout the upper Damariscotta River. At 500/m2 (Fig. 5b), growth is reduced in the middle of 1-ha farms, especially in low-current areas (red and light blue) and less so in the channel (darker blue). At very high densities (1000/m2, Fig. 5c), much reduced growth is predicted at all places, except in areas with the greatest current. Effect of Site and Density In this scenario (Fig. 6), time to market size from 26-g oyster seed planted at 500/m2 on week 31 ranged from 45 d to over 150 d, depending on where they were planted. In addition to outputs useful for shellfish farmers, by utilizing the expert interface, a number of outputs are available to scientists, extension agents and resource managers. These outputs include: • Detailed export of water velocity, direction and water depth for any point, area or transect in the GIS domain. • Output of shellfish physiological parameters from ShellSIM, FIGURE 5A. Percent reduction in growth of oysters in the middle of a 1-km2 patch from June to October when seeded at100/m2. FIGURE 5B. Percent reduction in growth of oysters in the middle of a 1-km2 patch from June to October when seeded at 500/m2. FIGURE 5C. Percent reduction in growth of oysters in the middle of a 1-km2 patch from June to October when seeded at 1000/m2. FIGURE 6. Time from seeding to market of 26-g oysters grown to 50 g when seeded on week 31 and planted on the bottom at 500/m2 at different locations in the upper Damariscotta River, Maine
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