Substantial advancement in aquaria rearing methods to assist recovery of an Endangered soft coral

Abstract

Abstract The temperate soft coral Dendronephthya australis has been listed as Endangered in NSW, Australia, owing to its restricted geographic range, rapidly declining populations, and a number of escalating threats. Research to assess practical methods for aquarium cultivation of D. australis for rehabilitation of wild populations is considered a high priority. Previous attempts at restoration by transplanting D. australis fragments have had limited success, but identified key challenges, which included achieving attachment to substrates and identifying appropriate foods to maximize survival. This study presents the results of experiments promoting the attachment of cuttings (nubbins) removed from donor colonies to moveable substrates (small concrete discs). Using a balanced orthogonal experimental design, three feeding regimes were tested: live artemia, live rotifers and dry powdered zooplankton. Donor colony survival and growth were also monitored over a 6 month period in the field. An overall nubbin survival rate of 100% was achieved under all three feeding regimes. Attachment rates were similar across feeding treatments, although nubbin behavioural responses (percentage of open polyps before feeding) suggested some preference for live rotifers. The cutting removal process had no significant effect on donor colonies in the wild, indicating that this is a sustainable approach for restoration. Overall, this study substantially advances the methodology for maintaining an Endangered azooxanthellate soft coral in aquaria and provides valuable input for management programmes aimed at implementing transplantation into the wild to aid species recovery.