Successful hatchery settlement of Blacklip Rock Oyster Saccostrea echinata single seed spat, without the use of epinephrine

The Blacklip Rock Oyster (BRO) Saccostrea echinata has demonstrated great potential for aquaculture across tropical Australia. This has resulted in considerable interest in farming BROs and the successful development of species-specific hatchery production processes. Now that BRO larvae can be consistently and reliably produced, the largest remaining bottleneck to large-scale spat production is the very poor rate of BRO settlement when using epinephrine as the settlement trigger. The use of epinephrine to induce settlement is now the standard practice in Australian oyster hatcheries and, with Sydney Rock Oysters, this results in highly successful, efficient, and effective process. Unfortunately, this has not been the case for BRO larvae and their response to epinephrine is so poor that each batch of larvae must be subjected to multiple epinephrine treatments. Even after years of dedicated BRO hatchery work and ongoing refinements to the epinephrine induced settlement process, settlement rates remain low – always below 20%. It is probable that repeated exposure to epinephrine causes considerable stress to the successfully settled spat and this could reduce their general health and robustness, making the spat more prone to post settlement mortality, and further reducing spat output. Recent trials at the Bribie Island Research Centre, using black builder’s plastic as a settlement substrate, have achieved proof of concept production of robust, epinephrine-free, single seed, BRO spat. This new approach to BRO settlement now provides a viable alternative option to using epinephrine. Although refinements are still being made to the design and configuration of the plastic settlement structures, the process has proven to be simple, efficient, and successful. The details of this settlement process are presented and discussed. Further trials will be undertaken to compare and quantify the rates of settlement, and post settlement performance, of spat settled with and without epinephrine.