Closing the lifecycle for the sustainable aquaculture of the bath sponge Coscinoderma matthewsi

Aquaculture of the bath sponge Coscinoderma matthewsi relies on collection of seed stock from the wild. This study investigated the potential of larval culture as a sustainable source of seed stock by quantifying reproduction, larval metamorphosis, and juvenile survival and growth of C. matthewsi. The accuracy of using surface area (2-dimensional) measurements as a proxy for juvenile growth was also assessed against volumetric (3-dimensional) data. Coscinoderma matthewsi is gonochoric and releases parenchymellae larvae over several weeks, corresponding with increasing sea surface temperatures, over the Austral summer (26.6 °C in November and 29.1 °C in January). Sexual maturity is size dependent and smaller individuals (1267.78 cm3 ± 405.66) were non-reproductive. There were no size differences between males and females and both sexes occur in equal proportions. Male reproductive output (ROI) (4.33% ± 0.75) was higher than females (1.62% ± 0.15). Larval metamorphic success was 98.0% ± 2 after 72 h post-release. Juvenile survival over seven months was independent of settlement density and ranged between 18% and 30%. Using surface area underestimated growth of juvenile sponges by approximately half in comparison to volume estimates. This study demonstrates larval culture as a sustainable source of seed stock to support large scale aquaculture operations.

► Reproduction, post-settlement survival and growth of a bath sponge were quantified. ► Increasing seasonal sea temperatures influences reproduction and larval release. ► Sexual maturity is size dependant with larger sponges being reproductive. ► Juvenile survival was high between 18% and 35% at 7 months. ► Volume is a more accurate proxy for sponge growth when compared to surface area.