22 March 2009 area, which receives sufficient water flow and food availability to promote high sponge growth. Identification of a suitable farming site was done at the Palm Islands and in Torres Strait, though only the results from the former location are discussed here. Sponges of Coscinoderma sp. and R. odorabile were farmed at six sites around three of the nine islands in the Palm Island group: Great Palm (1 site), Fantome (3 sites) and Pelorus Island (2 sites; Figure 1). At each site, about 50 sponges of each species were farmed in mesh panels. Farming started in August or October 2005 (winter in Queensland) and will continue for three years to investigate intra- and inter-annual variation in farming response. Sponges were monitored in situ every few months, with the last monitoring time occurred in January 2007. Mean sponge growth varied greatly among the six farming sites. For both species, farmed sponges grew best at the two Pelorus Island sites (Figure 5). After 15 months of farming, Coscinoderma sp. sponges were on average approximately four times their initial size at Pelorus 1, while R. odorabile sponges were almost six times their original size at both Pelorus sites. These growth rates were some of highest recorded for farmed sponges and clearly showed the potential of farming bath sponges at the Palm Islands. Although not as spectacular, growth rates of bath sponges at some other farming sites were also good. By January 2007, for example, R. odorabile farmed at Great Palm 1 had almost tripled in size. The experiment also showed that some farming sites in the Palms Islands were Fig. 4. An explant of Coscinoderma sp. growing away from the threaded line. This shape is not marketable. Fig. 5. Growth of Coscinoderma sp. and R. odorabile over time at the six Palm Islands farming sites. simply unsuitable for commercially farming sponges, such as Fantome 1 for Coscinoderma sp. and Fantome 3 for R. odorabile. Notably, both sponges were reasonably common on reefs adjacent to these two sites, indicating that the presence of a species at a site does not necessarily mean that the site will be suitable for commercial farming. Farmed sponges of Coscinoderma sp. and R. odorabile generally had similar growth patterns among the six farming sites, suggesting they had similar environmental requirements. Growth of both sponges also varied over time, with most growth occurring in the warmer summer months (December to May). Our farming study in Torres Strait also found that farmed Coscinoderma sp. grew best over the summer. Seasonal variations in environmental conditions such as food abundance and water temperature have been suggested to explain the seasonal variation in growth of temperate sponges. In tropical waters, environmental conditions fluctuate less over the seasons, but slight differences in food abundance over time, for example, may be sufficient to cause seasonal variations in growth. Our Palm Island study also showed that growth of farmed sponges could vary greatly between years (Figure 5). This finding indicated that production of bath sponges from a commercial farm would fluctuate from year to year, with lower production in years of poor growth. A good business plan that stockpiled bath sponges produced in good farming years and released them for sale during poor Fig. 6. Survival of Coscinoderma sp. and R. odorabile over time at the six Palm Islands farming sites. (Continued on page 70)
RkJQdWJsaXNoZXIy MjExNDY=