Growth and gonad development of the tropical black-lip pearl oyster, Pinctada margaritifera (L.), in the Gambier archipelago (French Polynesia) |
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| Authors: | Gilles Le Moullac Jér?me Tiapari Hinano Teissier Elodie Martinez Jean-Claude Cochard |
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| Institution: | (1) Laboratoire Domestication de l’Hu?tre perli?re, D?partement Lagon Environnement Aquaculture Durable en Polyn?sie Fran?aise, Centre du Pacifique, IFREMER, BP 7004, 98719 Taravao, French Polynesia;(2) Laboratoire d’Oc?anographie de Villefranche, Observatoire Oc?anologique de Villefranche, Quai de La Darse, BP 8, 06238 Villefranche sur Mer Cedex, France;(3) D?partement Environnement Littoral et Ressources aquacoles, Centre de Brest, IFREMER, BP 70, 29280 Plouzan?, France |
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| Abstract: | The growth and reproductive cycle of cultured black-lipped pearl oysters, Pinctada margaritifera (L.), were studied in the Gambier Islands (134°52′ W, 23°07′ S) from September 2002 to August 2003. Temperatures were recorded
throughout the year, revealing seasonal temperature variations between 22.3 and 27.8°C. The mean annual chlorophyll a value, as computed from satellite data, was 0.188 ± 0.075 μg L−1. To study growth and reproduction, 720 two-year-old individuals were ear hung on long-lines suspended at a depth of 7 m.
Samples were taken twice a month to obtain the following measurements: shell height; wet weight of flesh and total oyster;
dry weight of adductor muscle, mantle and visceral mass; and glycogen content. Gonad development was also studied by histology
on parallel samples. Growth was relatively fast during the first 6 months of the study: average shell height increased from
89.1 ± 9.1 to 119.7 ± 10.8 mm and total weight from 93.4 ± 24.5 to 155.1 ± 33.6 g, between September and the end of March.
Subsequently, from April to August, no significant growth was observed for shell and flesh, while the muscle weight decreased
significantly. Condition index (CI), defined as the ratio of wet weight of the visceral mass to shell weight, and histological
changes in the gonad revealed 3 significant reproductive events of different intensities. The analysis of correlations revealed
a specific effect of the chlorophyll a concentration on the growth of shell and soma, and one of the temperature on tissue glycogen content. This study also showed
also that CI could be an efficient indicator of reproductive events in pearl oyster. It thus appears that the development
of gonads goes on throughout the year in the Gambier Islands, without any detectable phase of sexual rest. |
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