ABSTRACT
The Pacific oyster (Crassostrea gigas Thunberg) is the most commonly farmed shellfish species worldwide with an annual production of 4,200,000 tonnes [1]. It is also one of the few shellfish species for which culture is based substantially on hatchery-reared juveniles. Oyster broodstock can be easily conditioned in hatcheries by manipulating temperature [2]. In natural populations, Pacific oysters spawn during summer months[3]. The ability to cryopreserve sperm of this species enables hatcheries to store sperm from individual males for selective breeding programmes [4,5]. Since adult oysters conditioned with ample food are often predominantly female [6], cryopreservation also provides a guaranteed supply of sperm for spat production outside the natural breeding season and reduces the costs associated with conditioning broodstock.
