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

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.

Impacts of necrotising disease on the Endangered cauliflower soft coral (Dendronephthya australis)

“…Branches ranged from 4 to 9 cm long. Collection causes no lasting damage to the colonies (Larkin et al 2023a). Whole colonies were not taken as has been previously done (e.g.…”

“…Root-like processes of Dendronephthya spp. can attach to solid objects and anchor in purely soft sediments (Barneah et al 2002;Larkin et al 2023a); however, it is unclear whether one method is preferable over the other for natural or assisted regeneration. Understanding the preferred habitat of this Endangered species outside of Port Stephens would greatly enhance our understanding of their ecology, and could allow for establishing populations in areas of Port Stephens that may be at a lower risk for sand inundation.…”

“…For example, populations of D. australis in Port Stephens, NSW, are not regenerating naturally and declines have continued for several years, suggesting that restoration is needed (Harasti 2016;Larkin et al 2021a). In fact, successful aquaculture and transplantation trials have already begun in these highly disturbed habitats (Larkin et al 2021b(Larkin et al , 2023a. In Botany Bay, it is unclear whether populations would regenerate naturally following loss of colonies.…”

Impacts of necrotising disease on the Endangered cauliflower soft coral Dendronephthya australis

“…Collection causes no lasting damage to the colonies (Larkin et al 2023a). Whole colonies were not taken as has been previously done (e.g.…”

“…In fact, successful aquaculture and transplantation trials have already begun in these highly disturbed habitats (Larkin et al 2021b(Larkin et al , 2023a. In Botany Bay, it is unclear if populations would regenerate naturally following loss of colonies.…”