2.4. THE POTENTIAL FOR ESTABLISHING A GIANT CLAM FARM WITHIN THE PROPOSED SEMPORNA ISLANDS PARK

This section is based mainly on a report produced for the Semporna Islands Project by Don Baker, a specialist in giant clam cultivation based in Kota Kinabalu, and with added information from Mark Wilson, Hatchery Manager at the Tropical Marine Centre, UK.


Figure 33. Giant clam culture is a feasible proposition for the proposed Park 2.4.1. Summary
There have been no attempts as yet to carry out any farming of giant clams in the proposed Semporna Islands Park. However, a feasibility study has indicated that it would be a viable, low impact form of mariculture very suitable for the area. Like seaweed farming, this type of mariculture can easily be carried out by local communities, and would provide economic and conservation benefits.

Either Pulau Selakan or Pulau Maiga are recommended as suitable sites for the hatchery and nursery. Seed shells from here would then be provided to the giant clam farmers for grow-out in the wild. Apart from the use of the clams for food and shells, the scheme could also produce specimens for re-stocking the reefs. Another possibility would be to supply live juveniles for the aquatic trade, where there is a high demand for quality specimens which have been cultured rather than taken live from the reef.

2.4.2. Background and rationale
Giant clams (Family Tridacnidae) occur throughout the Indo-Pacific, and are valued for food and for their shell. Years of uncontrolled harvesting have severely depleted populations of giant clams in many parts of their range, and there have even been local extinctions as a result of this long-standing pressure. It is for this reason that they are listed in Appendix II of the Convention on International Trade in Endangered Species, which means that international trade can be carried out only under permit.

Stocks of giant clams in Sabah, and specifically in the proposed Semporna Islands Park, have declined as a result of heavy collecting over many years (further details are in An Atlas of the Coral Reefs of the Semporna Islands). The largest giant clam species (Tridacna gigas) has been so badly affected that only a few individuals are thought to remain around Sabah's coasts and offshore reefs (Baker, personal observations).

It has been recommended in the Management Plan that collection of giant clams from the wild should no longer be permitted within the Semporna Islands Park, but that it may be possible to establish a giant clam farm, the aims of which would be to provide specimens for food and sale and to re-stock the reefs. It would be the first giant clam farm for Sabah and could act as a flagship project, encouraging other ventures to start up elsewhere in the State. Such a project would also bring socio-economic benefits and has the added advantage that, unlike some other forms of mariculture, it would have minimal environmental impact. The fact that giant clam juveniles require no supplemental feeding makes this mollusc an ideal candidate for mariculture. No other cultured seafood is similar. They do very little filter feeding because the primary source for their sustenance comes from the photosynthetic by-products released by their symbiotic algal "partners."

Giant clam sea farming has been carried out in the Pacific and Indian Oceans for the past 25 years. Some success has been achieved in getting private sector business and village communities to adopt this type of sea farming as a form of alternative fisheries protein supplement. Giant clam farms that are currently operating are selling mostly cultured Tridacna maxima, T. crocea, and T. squamosa juveniles as high value marine aquarium trade specimens. Few active giant clam farms are concentrating on the larger species (T. gigas & T. derasa) for food, but this has good potential.

2.4.3. Site suitability
The essential ingredients for rearing of giant clams are clean, clear water, stable conditions, natural sunlight, and security against poaching and predators. The proposed Semporna Islands Park is one of the most appropriate of several possible, mainly offshore, sites in Sabah that meet these criteria. The islands of Selakan or Maiga are seen as the most suitable locations for the holding tanks because they are already inhabited, so can provide a workforce and security. Also, this would leave the uninhabited islands of Sibuan and Mantabuan quiet and undisturbed, as recommended in the Management Plan.

Figure 35. Giant clams have been over-exploited and cultured clams could help to re-stock the reefs.2.4.4. Broodstock procurement, culturing and grow-out methods
Though the largest giant clam T. gigas has been targeted as the lead species for use in the development of small scale food fisheries enterprises for local fishermen, the second largest species and second fastest growing giant clam T. derasa is also a viable species to utilize. This is the main species cultured at the MMDC of the Republic of Belau in Micronesia. T. squamosa and S. maxima are most favoured for the ornamental trade because of their brightly coloured mantles. T. gigas is very rare in the proposed Park, but all the other species still occur in sufficient numbers to provide ample broodstock for culture.

Many years of research have been undertaken in giant clam farming by Australian institutions and by the MMDC [Micronesia Mariculture Demonstration Center] in the Republic of Palau [Belau], and the culturing techniques are well understood. Details are therefore not included here, but the essence of the operation is as follows:

The first step is to obtain eggs and sperm from wild stock. Traditionally, this is done by taking broodstock from the reefs and maintaining the animals in holding tanks until they spawn. A more direct method is to induce spawning in situ on the reef by injecting the animals with serotonin, which stimulates release of gametes. These can then be collected in plastic bags and taken to the farm where they are mixed so that fertilisation can occur (Wilson, pers. comm. 2001). This method would be especially relevant for the largest of the giant clams (T. gigas) because it is very rare and should be left on the reef.

Spawning giant clams can produce tens of millions of larvae at one session, but generally less that 10% survive for nursery grow-out operations. A 4000 litre concrete raceway can produce 50,000 to 100,000 / 3mm seed shells in 4 to 5 months.

Local communities on the islands within the Park would be supplied with ocean nursery cages about 12 months after the hatchery had begun, together with a supply of seedlings. Maintenance of each farm site would involve some 6 to 8 employees. The seedlings would be cared for until they reached marketable size (20cm average shell size) which would take about 3 years. Optimal harvest period for giant clam muscle and meat is 6 years from spawn to harvest.

Detailed costings, manpower requirements and profits have been calculated for a project in Bohol (Philippines) and show that giant clam farming can be a viable economic concern as well as bringing other benefits.


2.4.5. Budget
It is estimated that a fully operational giant clam hatchery & land based nursery [LBN] located on Pulau Selakan or P. Maiga will cost approximately $RM 700,000 to establish and run for two years. Two phases of installation are possible: if an eight raceway facility is chosen, then the overall costing will be reduced only from the stand point of man hour construction / labour and concrete. The difference in cost would probably be a reduction of $RM 50 to 60,000 only.

The $RM 700,000.00 figure estimate would include the following:

  • An independent hatchery & land based nursery facility producing no less than 2,000,000 viable seed shell/year for both ocean nursery and land based nursery applications
  • Living quarters for all staff
  • Training in all hatchery & farming aspects
  • Salaries for local staff for two years
  • Operations & consumable items for two years
  • Boats and motors
  • Infrastructure and equipment depreciation contingencies
  • Implementation of village-based ocean nursery programme


2.4.6. Marketing and reef replenishment
Clams can be used in a number of ways:

  • Live for the ornamental trade
  • Fresh meat - both mantle preparations & muscle
  • Vacuum packed meat
  • Dried mantle and muscle
  • Valued added shell sculptures, lamps and other items

Juvenile clams about 9 months old can be used live for the ornamental trade and specimens to replenish the reefs could be one or two years old, provided they could be protected from poaching. For food there would need to be a latent period of 3-4 years before production comes 'on-stream'. Food sales can cater to Sabah and West Malaysia's growing tourist industry, providing gourmet dishes in local restaurants, but exports would also provide important sources of revenue.