Effects of sperm to egg ratio, stocking density, delay of gamete contact, temperature and salinity on fertilisation success and D-larvae production of green mussel, Perna viridis

ABSTRACT

Mariculture of green mussel (Perna viridis) is being hindered by reliance on seed from the wild. Hatchery production helps increase seed stock, but little is known about the factors that may affect hatchery practices. Development of hatchery protocols to optimise production is therefore needed. This study determined factors affecting fertilisation and survival at the D-hinged stage namely: sperm to egg ratio; delay in gamete contact; egg stocking density; temperature; and salinity. Results indicated that maximum fertilisation and survival at the hinged stage was achieved at 50:1 sperm to egg ratio. Stocking density variation between 20 and 50 eggs mL⁻¹ had no significant effect on fertilisation, however, there was significantly higher survival from fertilised egg to the D-hinged stage at 20 eggs mL⁻¹ than at 50 eggs mL⁻¹ with non-significant reductions at 30–40 eggs mL⁻¹. Delay in gamete contact significantly affects fertilisation but not D-hinged survival. Fertilisation was significantly higher one hour after gamete liberation, but declined thereafter. Mussel eggs were successfully fertilised at varying temperatures from 25°C to 35°C, while a higher fertilisation rate was observed at a salinity of 28–31 ppt. For survival to the D-hinged stage, optimum temperature and salinity ranged from 28°C to 30°C and 28–31 ppt, respectively.

KEYWORDS:

• Bivalve
• gamete liberation
• fertilised egg
• egg incubation
• embryonic development
• hatchery production
• viability of oocytes
• normal larvae
• motility
• polyspermy

Acknowledgements

The authors would like to thank the Department of Science and Technology-Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development (DOST-PCAARRD) for the research fund and the Institute of Aquaculture, College of Fisheries and Ocean Sciences, University of the Philippines Visayas, for the use of facilities. Special thanks to Dr. Liah C. Catedrilla for patiently reading the manuscript, Professor Roman C. Sanares for the statistical advice, and Joel Fabrigas and Argie Nicmic for the help extended during the conduct of the experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Department of Science and Technology-Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development (DOST-PCAARRD). (http://www.pcaarrd.dost.gov.ph/home/portal/index.php/about-pcaarrd).