Research & Development

  • Giant Clam

    Remarkable abundance and dominance of Tridacna maxima have been reported in several remote islands and atolls of French Polynesia and these natural stocks are now exploited.

    To achieve the sustainable development of this extraordinary natural resource, genetics, pathology (for translocation), stocks estimations, stocks co-management including technical, economical and socio-cultural parameters have been investigated since 2002.

    Clam-mountain_sBottom structure of Tatakoto atoll (Photo courtesy of Yannick Chancerelle). The lagoon floor of the new no-take-area (insert) is coverd by Mounts of giant clams as revealed by a 4-meter resolution IKONOS (copyright Space Imaging Inc.) satellite image. Record densities have been measured in this area (544 individuals per m², (Gilbert and al, 2005). Stock assesment using in situ and remote sensing data was done by IRD.

    CollectageBenitiers_sGiant clam spats are collected in Eastern Tuamotu (photo Laurent Yan)

    Aquaculture applications, spat collection techniques, rearing techniques, transport and stock enhancement techniques have been tested and mastered in several Eastern Tuamotu atolls.

    4 years old Tridacna maxima collected and reared (L = 11 cm). (photo Laurent Yan)

     

    Stock enhancement and restocking assays were successful. 36000 reared juveniles (from spat collection) have been relocated in various locations of their lagoons: 60 to 85% survived after one year. And on these patches of restocked clams, up to 12% of new juveniles have settled on the restocked areas.

    Example of patches of stock enhancement of giant clams in Tatakoto lagoon. (photo Laurent Yan)

    Bibliography :

    Andréfouët S., Gilbert A., Yan L., Remoissenet G., Payri C., Chancerelle Y. (2005) The remarkable population size of the endangered clam Tridacna maxima assessed in Fangatau atoll (Eastern Tuamotu, French Polynesia) using in situ and remote sensing data. ICES Journal of Marine Science. Vol. 62, Issue 6, Pp 1037-1048.

    Gilbert A., Yan L., Remoissenet G., Andréfouët S., Payri C., Chancerelle Y. (2005) The world-record giant clam density under protection in Tatakoto atoll (Eastern Tuamotu archipelago, French Polynesia). Coral Reef. 24 : 495.

    Gilbert A., Remoissenet G., Yan L., Andréfouët S. (2006, in press) Singularités et promesses du bénitier, Tridacna maxima, en Polynésie française. Fisheries Newsletter.SPC information bulletin.2006.

    Gilbert A.,Andréfouët S., Yan L., Remoissenet G. (2006, in press) The giant clam Tridacna maxima communities of three French Polynesia islands: comparison of their population sizes and structures at early stages of their exploitation, ICES Journal of Marine Science, doi:10.1016/j.icesjms.2006.07.001.

    Laurent V., Planes S. and Salvat B. (2002) High variability of genetic pattern according to loci in giant clam (Tridacna maxima) within French Polynesia. Biol. J. Linnean Soc. 77. 221-231.