RECRUITMENT SUCCESS OF PACIFIC OYSTERS Crassostrea gigas IN RELATION TO TROPHIC QUALITY, LARVAL QUALITY AND METAMORPHOSIS DELAY

Alana Correia-Martins*, Franck Lagarde, Nabila Guenineche, Gabriel Devique, Anaïs Crottier, Stéphane Pouvreau, Emmanuelle Roque d'orbcastel, Masakazu Hori, Masami Hamaguchi, Toshihiro Miyajima, Jean-Bruno Nadalini, Réjean Tremblay
Institut des sciences de la mer de Rimouski
Université du Québec à Rimouski
Rimouski, QC, Canada G5L 3A1

E-mail: Alana.Correia-Martins@uqar.ca

In the Mediterranean Thau lagoon, while the shellfish industry is interested to develop spat collection activity, we observed an important fluctuation in recruitment success of pacific oysters (Crassostrea gigas) at the micro-geographical scale. Between 2012 and 2014, metamorphosis delays have been reported, with 40% variability of the size at metamorphosis between sites. We suggest that metamorphosis success is dependent on the sufficient amount of energy reserves accumulated by competent larvae (pediveliger) affected by the trophic resources quality. We test the hypotheses that 1) the larvae delay their metamorphosis when trophic condition is not optimal and 2) the sites with higher recruitment success was characterized by settlers showing higher quality in terms of energetic reserves. During spatfall event, collectors were installed in six experimental sites inside and outside the shellfish culture areas in the lagoon. Abundance and lipid content of young settlers (pediveligers and post-larvae) were determined two weeks after their installation and spat abundance four weeks later. Results showed heterogeneous recruitment rates between sites inducted by different settlement and recruitment processes which are under environmental factors (Fig. 1). A decrease in energy reserves of young settlers linked to metamorphosis delay may cause a failure of metamorphosis and a decrease in the recruitment success. Current lipid quantification analysis will attempt to establish a link between C. gigas recruitment, survival at metamorphosis, energy reserves of young settlers and lipid quality of the trophic resource. A better understanding of these interactions could allow the development of better spat collection management in lagoon environments, and contribute to the general understanding of the ecological and physiological mechanisms of settlement and recruitment in contrasted and changing environments.