Spatial variability in community structure of dictyoceratid sponges (Class Demospongiae; Order Dictyoceratida) was examined on coral reefs in Torres Strait, an archipelago of islands and reefs between northern Queensland, Australia, and Papua New Guinea. Dictyoceratid sponge abundances and environmental parameters were recorded at 4 locations, separated by 50-220 km. Each location was subdivided into 5-7 sites, each ≥2 km apart. At each site four 50x2 m belt transects were quantitatively surveyed, recording dictyoceratid numbers, substrate type (rock, rubble and sand), water clarity, degree of reef slope and depth. Dictyoceratid abundance was similar among locations, averaging 15.5 individuals per 100 m2, but varied significantly among sites. Twenty three dictyoceratid species were recorded in Torres Strait, with approximately half (12/23) found in only one location. Canonical Correspondence Analysis determined that the measured environmental factors explained only 26% of the spatial variation. Cluster analysis revealed a complex dictyoceratid community structure with consistent patterns among neighbouring sites and among sites separated by hundreds of kilometres. Conversely the dictyoceratid community could vary greatly between neighbouring sites 2 km apart and on the same reef complex. The results of this study suggest that spatial variability of dictyoceratid sponges in Torres Strait is influenced by a combination of environmental, biological and stochastic processes.
A series of farming experiments were done in Torres Strait using the common bath sponge Coscinoderma n. sp. to establish commercially viable culture procedures. The first experiment compared several farming methods and found that mesh panels promoted greatest sponge growth and survival, probably because they cause minimal tissue damage. Using mesh panels, a subsequent experiment examined the importance of farming site and season of transplant. Sponge growth and survival were similar between the three farming sites, while growth was highest for explants transplanted at the end of winter. These explants doubled in size on average in 6 months. The final experiment examined the optimal explant size to transplant and found that 'medium sized' explants (104 cm3) have good growth and survival, and permit high explant production from a given amount of sponge biomass. This study has identified good farming procedures, and coupled with the high growth rates of Coscinoderma n. sp., it suggests that bath sponge aquaculture in Torres Strait will be a viable industry.