Markus Paster

Mariculture trials with Mediterranean sponge species: The exploitation of an old natural resource with sustainable and novel methods

Abstract The growing interest in bioactive compounds for new drugs resulted in a notable research boom on secondary metabolites from marine invertebrates, especially from sponges. Some sponge species display promising antibiotic and antitumour activities. Natural stocks, however, are not capable to satisfy the potential demand by pharmaceutical industries without being heavily degraded. Within the scope of the European Commission (EC)-funded NOvel MArine TEChnologies (NOMATEC) project, a new method for farming sponges has been developed and tested in order to ensure the sustainable supply of sponge raw material without harming the marine ecosystem. Various Mediterranean sponge species with promising bioactive metabolites are tested for their suitability for aquaculture. Special trays were designed as mariculture units using metal/net grids. In total, 708 cuttings from four different species were farmed in mesh on various installations exposed off the marine biological station, Station de recherches sous marine et oceanographique (STARESO), in the Bay of Calvi, Corsica. All sponges were regularly mapped using a digital UW camera to monitor survival and health. Growth rates were determined by weighing the sponge samples (drip-wet weight, DWW) as well as by calculating their projected body area using digital imaging software. Within the first 12 months, species taken in aquaculture exhibited promising survival rates of up to 98%, indicating the general suitability of the applied farming design. In contrast to former findings, Ircinia variabilis exhibits high survival rates (75% in 12 months) and reveals remarkable growth rates (up to 200% in 12 months). A correlation between the drip-wet weight and the projected body area of cuttings from two species was detected and discussed. Based on the results of the first project year, farming design and conditions will be improved and knowledge gaps concerning sponge autecological questions will be filled during the next phases.

Defecation behaviour of the Lined Bristletooth Surgeonfish Ctenochaetus striatus (Acanthuridae)

The feeding and defecation behaviour of the surgeonfish Ctenochaetus striatus was investigated at Ras Mohammed National Park (South Sinai, Red Sea). The fish feed on coral rock mainly by sweeping loose sediment with their flexible broom like teeth into their mouths. Feeding occurred exclusively on coral rock, but defecation took place only outside the grazing area above sand in small, precisely defined areas.