20 March 2009 Farming bath sponges in tropical Australia Alan Duckworth1*, Carsten Wolff and Elizabeth Evans-Illidge Why farm bath sponges? Global demand for bath sponges for cosmetic, bathroom and industrial use, far exceeds supply. Commercial bath sponges, species from the order Dictyoceratida that have a high quality spongin skeleton, have traditionally been harvested from natural populations in the Mediterranean Sea and around Florida, USA. Overharvesting and periodic disease outbreaks have decimated these natural populations and severely limited the yield of bath sponges. Because current harvest levels from natural populations cannot meet demand, there is an opportunity to develop alternative supply methods. In-sea aquaculture is one option that could supply sufficient and sustainable quantities of bath sponges to meet the market shortfall. Studies from Australia, New Zealand, Micronesia and the Mediterranean Sea have shown that sponges can be experimentally farmed using simple methods and cheap equipment, thus suggesting that bath sponge farming could be a cost efficient commercial industry. In addition, bath sponges can be processed or cleaned for sale using simple techniques, are non-perishable, need minimal storage requirements and can be transported easily. These factors suggest that bath sponge farming maybe an appropriate industry for development in remote coastal indigenous communities in Australia. The potential for bath sponge farming in tropical Australia has been explored at two northern Queensland locations (Figure 1), the Palm Islands, situated 70 km north of Townsville, where the Australian Institute of Marine Science (AIMS) is located, and Torres Strait, situated between Cape Yorke and Papua New Guinea. Two bath sponge species, both possessing soft, durable fibers, were experimentally farmed: Coscinoderma sp. and Rhopaloiedes odorabile (Figure 2). Both species were farmed at the Palm Islands, while only Coscinoderma sp. was farmed in Torres Strait (R. odorabile is not present in Torres Strait). Indigenous Australians have been engaged in every stage of the research, including helping out with experimental work. In Torres Strait, sponge divers from the local community were able to SCUBA dive and participate in all underwater work with AIMS scientists. This approach has promoted the transfer of skills and technology from each study to the local indigenous community. At both locations, sponges were obtained for farming experiments by partially harvesting a small number of wild sponges from the local populations. Similar to most sponge Fig. 1. Map of Queensland showing Torres Strait and the Palm Islands, including the three islands used for experimental sponge farming. species, Coscinoderma sp. and R. odorabile have remarkable regenerative abilities and can survive two-thirds of their biomass being harvested as long as the harvested portion is removed cleanly with a sharp knife and the basal area remains attached to the substrate. These sponges will re-grow the harvested portion in one to three years. The harvested portion can be further cut into smaller pieces or explants for farming. It is important that at least one side of each
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