A giant clam stock survey and preliminary investigation of pearl oyster resources in the Tokelau Islands
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A stock survey of the two species of giant clam, Tridacna maxima (fahua nao) and T. squamosa (fahua taka) was carried out between 18 May - 15 June 1989 at the three atolls of Tokelau: Fakaofo, Nukunonu, and Atafu. The field surveys utilised small boats belonging to the Department of Agriculture and Fisheries. The survey team consisted of the author and Fisheries Officer covering all the atolls and Agriculture casual assistants at each atoll. A surface tow method was employed (2 divers, one each side of the boat) to count clams over measured distances. Tows were made around the perimeter of the lagoon reef covering depths up to 12-15m, around patch reefs in the centre of the lagoons, and two tows on the ocean side of each atoll. In addition, reef flat transects were made to determine clam densities over these large shallow areas bordering the lagoon. The following number of tows; reef flat transects were made: Fakaofo - 72;3, Nukunonu - 61;3, Atafu - 35;2. A preliminary investigation was also made to look at the presence of stocks of the black-lipped pearl oyster, Pinctada marqaritifera in the three atoll lagoons. Here, SCUBA was used to make dives from patch reefs or bommies in the lagoon to a maximum depth of 120ft [36m]. Densities of pearl oysters and spiny oysters (Spondylus sp.) were recorded at several depths down to 100 [30m] or 120ft. No live or dead pearl oyster shells were found in any of the atolls. Densities of Spondylus sp. were high at dive sites in Fakaofo lag oon (32–56/m2) but considerably less at Nukunonu (<1/m2) and Atafu (0–4/m2). The densities at Fakaofo indicate potential competition (for food and settlement) with spiny oysters if pearl oyster introduction is attempted. At Atafu specimens of the small species Pinctada maculata were found.