Diet Composition of Two Temperate Calcareous Sponges: Leucosolenia echinata and Leucetta sp. from the Wellington South Coast, New Zealand

Abstract

Aquaculture trials were conducted in the East Aegean Sea with Dysidea avara and Chondrosia reniformis to test the possibility of growing these sponges in the vicinity of sea-based fish farms. Culturing sponges in the vicinity of fish farms may have two benefits: the sponges may grow faster due to an increased availability of organic food and the pollution caused by the fish farms is remediated by the filtering activities of the sponges. An initial trial was conducted to compare growth of the two sponge species under floating fish cages to growth in a natural, pristine environment. Explants of D. avara were grown suspended on nylon threads, explants of C. reniformis were grown in cages constructed of stainless steel. After being one year in culture, nearly 100% of all explants of D. avara survived. Growth was highest underneath the fish cages, but growth rates were low compared to earlier studies. For C. reniformis survival at the pristine site was 100%, and growth was estimated at 800% per year. All explants cultured underneath the fish cages died due to smothering with sediment. After the initial trial, a new, cost-saving and growth promoting method for D. avara was tested at the fish farm location. Explants were grown on PVC pins that were mounted into a metal frame. Growth of the sponges on the pins was eight times faster than that of sponges growing on threads. We conclude that culturing D. avara under floating fish cages is feasible when using the new methodology.