Developing methods for commercially farming bath sponges in the Palm Island group, central Great Barrier Reef

Brief description

In August 2005, experimental farming of the sponges Coscinoderma sp. and Rhopaloiedes odorabile commenced at three of the nine islands of the Palm Island group in the central Great Barrier Reef: Great Palm Island (1 site), Fantome Island (3 sites) and Pelorus Island (2 sites).Eleven farming techniques were tested. These were grouped into four general categories: threaded line, cut explant, spike and mesh panel methods. Within each category different materials such as nylon, polyethylene and polypropylene lines or different compartment sizes were trialled.Sponge explants were obtained by partially harvesting approximately 20 sponges of each species from the local populations, keeping the sponges underwater at all times. Both Coscinoderma sp. and Rhopaloiedes odorabile explants were deployed within 2 x 2 m plastic grids, suspended upright 3 m from the substrate at an average depth of 12 m. Three grids were used per sponge species, each holding 5 replicates of each treatment (farming technique). Survival and growth of the explants were monitored in situ every few months over a period of 2 years to determine if there were also seasonal differences.The importance of a nursery period for Coscinoderma sp. and Rhopaloiedes odorabile was examined by comparing growth and survival of explants threaded onto 4 mm nylon line, explants farmed in mesh panels and explants placed in mesh panels for 4 months then threaded onto nylon line. Explants were obtained by partially harvesting approximately 5 individuals of each species. For both species, 5 replicates of each treatment were used. The ropes or mesh strips were >= 1 m apart, in an upright position at a depth of approximately 12m. Each method replicate had 5 explants approximately 15 cm apart. The explants were farmed for a period of 9 months.
An experiment was carried out to test a range of farming techniques at different locations within the Palm Island group, to determine the most successful method and location for commercially farming Coscinoderma sp. and Rhopaloiedes odorabile. For both species, a second experiment was carried out to determine whether growth and survival using the threaded line technique, was higher in explants, which were first allowed a 'nursery period' during which explants were allowed to heal in mesh panels.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: Line methods:For the two line methods, nylon, polyethylene and polypropylene lines were tested. Lines were 4 mm thick, about 20 cm long, with one explant situated at mid-length.Threaded line method - a hollow needle was used to thread line through the middle of each explant. Cut explant method - the explant was first cut halfway through, allowing the line to be pushed down into a slot, then thin cotton thread was used to sew the cut ends of the explant together. The cotton would disintegrate within several weeks by which time the two cut sides would rejoin.The spike method:Sponges were farmed on 15cm long, 0.5 cm wide, cross shaped pieces of PVC or polyethylene plastic that were sharpened at one end. An explant was pushed onto the spike so that it rested on the plastic base.Mesh methods:Mesh bags, aquapurses (Tooltech Pty Ltd) and mesh panels (Australian NetMakers) were compared. The mesh bags were made from 1 mm thick nylon strands with mesh size of 3 cm and each contained 1 explant. Both the aquapurse and mesh panels were broken down to small containers each holding 1 explant. The final dimensions of the aquapurse were 15 x 20 x 10 cm and the mesh panel 15 x 10 x 5 cm. The mesh size was 1.5 cm for the aquapurse and 4 cm for the mesh panel. Strand thickness was similar for both, about 3 mm.

Notes

Credit
Duckworth, Alan R, Dr (Principal Investigator)