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The University of the Philippines (UP) is the country’s national university. This premier institution of higher learning was established in 1908 and is now a university system composed of eight constituent universities and one autonomous college spread throughout 17 campuses in the archipelago.



Culture of the true giant clam Tridacna gigas for conservation in the Philippines: proceedings

Gomez, E.D.; Licuanan, S.S.M.; Quaoit, H.A.R. (Philippines Univ. Diliman, 1101 Diliman, Quezon City (Philippines). Marine Science Inst.);

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Tridacna gigas, the true giant clam, once abundant in the Philippine seas, was rendered virtually extinct by unregulated and illegal harvesting activities of commercial fishermen and poaches. Today, through mariculture and perseverance, the species may yet be reestablished using cultured giant clam seed from imported cultured stocks. Two cm juveniles of T. gigas spawned in October 1985 were imported from Australia in 1987, reared in wooden raceways, then transferred to the ocean nursery, where they exhibited growth rates of 8 cm per year. tridacnids are generally protandric hermaphrodites, developing male gametes first, followed by development of female gametes. The Australian cohort of T. gigas was male mature in 1991, and reproductivity mature (containing sperm and eggs) in 1995. Spawning of broodstock clams (about 50 cm shell length) was induced by injection with serotonin intragonadally, releasing 100 million eggs. Initially, succesive larval and juvenile mortalities were very high, with only a few hundred survivors at ocean nursery rearing stage. Since then, this Australian cohort, now 12+ years old, has been successfully spawned every year, releasing up to 200 million eggs per spawning. Several cohorts of T. gigas larvae were also imported from the Solomon Islands and reared in cement and canvas raceways, with thousands of subadult and male mature clams ranging from 20 to 57 cm shell length now being reared in the ocean nursery. Juveniles and subadul
ts of the different T. gigas cohorts were used in transplantation/reseeding activities in selected sites in the Philippines, from Pangasinan in the north, to Tawi-Tawi in the south, from Pagasa Island (Spratlys) in the west to Samar in the east. Reseeding activities were often conducted with cooperators. Survival of transplant varied, influenced by natural and human factors. This study showed that long-living species such as T. gigas can be reared to sexual maturity to produce clam seed. For restocking purposes, clam seed is an obvious product of a giant clam hatchery. Other potential products that may be useful to clam farmers either for restocking or commercial purposes are larvae (for those with existing hatcheries), subadults and even broodstock