Factors affecting settlement, growth and metamorphosis of hatchery-produced Australian blue mussel larvae

The irregular supply of natural mussel seed for aquaculture has seen an increase in the establishment of hatcheries to produce a reliable source of mussel seed. While many of the factors influencing fertilisation and early survival of hatchery-produced mussel larvae have been explored, little is known about the factors influencing the success of larvae during settlement and development under hatchery conditions. This study examines the effects of feed concentration, airflow rate, rope type and larval stocking density on the growth, settlement and development of Australian blue mussel larvae under hatchery conditions. Manipulation of feeding concentration at the time of settlement (25,000 cell ml −1 , 50,000 cell ml −1 , 100,000 cell ml −1 and no feed) had little effect on growth, settlement and development of larvae, due to reduced feeding behaviour during this period. In contrast, high airflow rates were found to increase settlement and larval development but did not influence growth. Larvae also show significantly greater settlement rates on more filamentous ropes compared with those on less filamentous rope types. We also detected a strong inverse relationship between larval density and size at settlement, suggesting density-dependent competition may reduce growth under hatchery conditions. These results indicate optimal conditions for settlement and development of mussel larvae in hatcheries may be achieved by decreasing feed concentration during the settlement phase, increasing airflow rates and maintaining moderate densities of larvae. These optimised hatchery conditions have the potential to improve yields while simultaneously reducing production costs.