Ecophysiological model of growth and reproduction of the black pearl oyster, Pinctada margaritifera: potential applications for pearl farming in French Polynesia

Ž . A model of bioenergetics of the black pearl oyster Pinctada margaritifera was built to simulate growth, reproduction and spawning in suspended culture at field sites in Takapoto lagoon Ž . French Polynesia . This model was based on allometric scaling of physiological functions and Ž . Ž y1. scope for growth SFG calculations. The input functions were clearance rate CR, l day , Ž . retention efficiency RE, % for each kind of particle encountered in suspended matter, pseudofaeŽ y1. Ž ces and faeces productions PF and F, mg C day , excretion and respiration rate U and R, mg y1. Ž y1. C day . The assimilated carbon i.e., SFG, mg C day was partitioned to the three internal Ž . state variables somatic tissue, shell and gonad according to the asymptotic increase of the Ž . reproductive effort ER, % with the age. Given organic and mineral particulate matter in Ž y1. suspension in lagoon water POM and PIM, mg L and assuming that the taxonomic composition of POM was fairly constant throughout the year, the model predicted annual Ž . Ž . evolution of total tissue weight W , g dry weight , shell weight W , g DW and gonad Tissue Shell Ž . weight W , g DW of pearl oysters at various ages. Data on tissue and shell growth, but also Gonad on gonad development of cultivated pearl oysters, acquired in 1997–1998 in Takapoto lagoon, were used to validate the model outputs. Results of the simulations indicated that the P. margaritifera growth model provided realistic growth trajectories for shell, somatic tissue and gonad, for pearl oysters aged from 1 to 4 years. ) Corresponding author. CREMA, BP 5, 17137, L’Houmeau, France. Tel.: q33-5-46-50-94-40; fax: q33-5-46-50-06-00. Ž . E-mail address: [email protected] S. Pouvreau . 0044-8486r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00373-7 ( ) S. PouÕreau et al.rAquaculture 186 2000 117–144 118 For scientists, this validated model is very useful to understand more extensively feeding processes and reproduction features of P. margaritifera in Polynesian lagoons. It provides also valuable information for pearl farmers and for management of cultured populations, especially concerning the time to produce a pearl, spat collection, density in system culture, choice of farming site and carrying capacity of the whole lagoon. In this respect, the model demonstrates Ž y1. that local overdensity must be avoided especially when water current is low -1 cm s and that global consumption of the cultivated pearl oyster stocks plays a insignificant role in comparison with the consumption of all the natural bivalves occurring in the lagoon. Nevertheless, this first growth model developed for P. margaritifera was only validated for a Takapoto atoll and presents several limitations concerning especially the temperature effect and the range of food concentration. Consequently, some improvements will be necessary to apply this work to other pearl farming sites in French Polynesia. q 2000 Elsevier Science B.V. All rights reserved.