INFLUENCE OF PHOTOPERIOD AND AERATION ON THE GROWTH, SURVIVAL, AND EARLY SPAT SETTLEMENT OF THE HATCHERY-REARED GREEN MUSSEL Perna viridis

One problem that hinders sustainability of mussel production is the availability of seed supply. The farming of mussel is dependent on the collection of wild spats settled on their substrates. Furthermore, mussel larva develops into a pediveliger after 16-20 days, a stage preceded by the development of an eyespot and foot. This is the time by which the veliger larvae metamorphose from a swimming larvae to a bottom dwelling juvenile (spat). This is the most crucial period of the hatchery where the culture is prone to larval crashes. Hence, in an attempt to induce early spat settlement and improve mussel seed production in the country, this study aims to determine the influence of photoperiod and aeration, on the growth, survival and settlement of green mussel (P. viridis).

Pediveligers were exposed in 24L:0D h (light: dark), 12L:12D h and 0L:24D h conditions for the photoperiod experiment. Three aeration intensities were also tested - mild (10 liters·hr^-1), moderate (20 liters·hr^-1) and strong (30 liters·hr^-1).

Highest growth and survival rates were observed in P. viridis spats grown in 0L:24D hours photoperiod. There was no significant difference in the settlement rate of larvae exposed to different photoperiods. Mild aeration has shown to improve the growth of P. viridis larvae but higher survival and settlement rates were attained in the strongly aerated conditions. Therefore, when the larvae starts to settle, it is recommended to expose them to darkness and provide a strong aeration to be able to attain high survival and settlement rates, and bigger spats.