Influence of lunar cycle, moon driven tides and water physicochemical factors on the gonadal maturation of green mussel, Perna viridis, in the inner Malampaya sound, Taytay, Palawan, Philippines

This study determined the influence of the lunar cycle, tidal fluctuation, as well as water physicochemical factors on the gonadal maturation of green mussel, Perna viridis , in Malampaya Sound, Taytay, Palawan, Philippines. Monitoring and sampling were conducted for the 6 months, from October 2017 to March 2018. It was observed that the lunar cycle has a direct influence on gonadal maturity. Gonadal changes in both male and female P. viridis were observed histologically and both exhibit the characteristic of lunar-synchronous pattern.  It was observed that a high number of green mussels with spawning stages usually occur during the full moon and new moon. Furthermore, gonadal maturity was also affected by the tidal fluctuation. A higher number of P. viridis with spawning stages were recorded during spring tide, whereas the percentage of spent individuals were higher during neap tides. Furthermore, it was observed in the present study that salinity fluctuation could influence spawning of green mussel, wherein the number of spent individuals increased after the sudden drop in water salinity from 30 to 13 ppt after the heavy rainfall, an indication that spawning had occurred. The presence of individuals with spawning stages was also observed throughout of period of sampling which indicates that mussels were continuously breeding in the area. The highest percentage of individuals having spawning stages were recorded in October and November. The information on the factors that affect gonadal maturation and spawning schedule can help mussel growers predict the schedule of spatfall.