Use of relaxants to obtain saibo tissue from the blacklip pearl oyster (Pinctada margaritifera) and the Akoya pearl oyster (Pinctada fucata)

Cultured pearl production requires mantle tissue ('saibo') from donor oysters to be grafted into a number of recipient oysters. Use of anaesthetics is essential to keep donor pearl oysters alive for further utilisation and to minimise damage to them while excising saibo tissue. Propylene phenoxetol and benzocaine were chosen as relaxants as they have proven effective with pearl oysters over a short period of time and allow rapid recovery without mortality. Pinctada margaritifera and Pinctada fucata were exposed to propylene phenoxetol at a concentration of 2.5 mL L−1 and benzocaine at concentrations of 250, 500 and 1200 mg L−1. Once relaxed, oysters were observed every 5 min to evaluate the condition of the tissues. Oysters were classified as either 'suitable saibo donor' or 'non-suitable saibo donor' depending on their suitability for use as saibo donors for pearl production. Survival of oysters in all treatments was 100%. With the exception of oysters exposed to 250 mg L−1 of benzocaine, where no relaxation was recorded, oysters in all other treatments became relaxed and showed good condition and acceptable characteristics to be used as saibo donors.