By Antoine Teitelbaum, Paul C. Southgate, Andrew Beer, Poasi N Fale and Martin Finau

 

In May 2008, the SPC aquaculture officer went to Tonga to provide assistance to two projects aiming at stimulating the small-scale half pearl (mabe) industry that is present in the Vava’u group of Tonga.

A pearl shell carving training workshop was organized by SPC in Vava’u and involved local craftsman and woman whom wished to improve their pearl shell and mabe handicrafts production. Tokerau Jim, a master carver from Rarotonga, Cook Islands, was contracted by SPC to deliver the highest possible quality, hands on, training.

Following the workshop, a hatchery rearing run of winged pearl oyster (Pteria penguin) was undertaken in Tongatapu at the Sopu maricultre center. This was conducted as part of an ACIAR funded project for which James Cook University (JCU), Australia is the commissioned organization and Professor Paul Southgate is the Project Leader. Technical assistance for the hatchery work was provided by Andrew Beer and Paul Southgate of JCU and the SPC aquaculture officer, Antoine Teitelbaum. The spat produced by the end of this run, will be used to supply the Vava’u pearl farmers and thus increase the supply of raw material of pearl shells and mabe. They will also be used in experiment to fine tune culture and mabe production methods.

History of Pearl farming in Tonga 

Cultured pearls in the Pacific are dominated by the black pearl which is produced from the black-lip pearl oyster (Pinctada margaritifera). In Tonga, Pearl oyster culture began in the early 1960s. In 1975 an experimental venture was set up by the Tongan government. Broodstock of the winged pearl oyster (Pteria penguin) was imported from Japan for initial culture trials. The FAO South Pacific Aquaculture Development Project (SPADP) provided assistance in 1989 in carrying out stock assessment, spat collection surveys and grafting techniques.  

Commercial Feasibility of Pearl Farming in Tonga, was initiated in 1993. Japanese specialists estimated that an area of approximately 850 ha in the Vava'u island group could be farmed for half-pearl production supporting annual production of around 750,000 pearls, with approximately 30% of these being first-grade. Assuming a value of US$30 each for first-grade half-pearls, potential annual revenue from an area of 850 ha. was estimated to be around US$7.5 million (Finau, 2005). 

Tonga is in a relatively unique position to diversify the range of pearl product because the island of Vava’u has winged pearl oysters (Pteria penguin) from which half-pearl (mabe) can be produced. One of the advantages of producing half-pearls is the lower capital and technology investment required and the value-added opportunities through jewelry and handicrafts. Already there is a small but thriving niche market to sell mabe pearls to tourists in Vava’u.

The SPC Aquaculture Section targets livelihood opportunities. Mabe pearls and carved shell products are one of the lucrative opportunities supporting sustainable and profitable small scale and rural development, especially in areas where tourism is developing.

In June 2006, in Kiribati, SPC aquaculture section, together with JCU organized a similar carving workshop to introduce the basics of those techniques (Teitelbaum, 2007). This present carving workshop was a more advanced course and had two major goals: (i) to provide an overview of the fundamentals involved in pearl jewelry and handicraft (tools and craftsmanship, jewelry and handicraft design, pearl handicraft preparation and setting and marketing techniques) and (ii) pay particular attention to the domestic market opportunities and local cultural carving and handicraft traditions of the Vava’u.

Tokerau Jim (www.tokeraujim.com), the master carver hired for this exercise, runs a successful business in the Cooks. For the occasion, he brought in some specific tools that he uses in his workshop in Rarotonga. The Taurus ring saw[1] and the Foredom hand drill[2] were the most noticeable technological improvement that were brought to Vava’u. Traditionally, carvers were using hand grinders and hacksaws for producing their crafts, taking over 30 minutes to produce shapes out of a shell when a ring saw can produce a shape in less than a minute. Furthermore, the Foredom hand drills (which rpm rate is over 45 000 compared to 30-33 000 for standard hand drills) allows carvers to be a lot more precise in their motifs and carvings.

Over this 3 day event, trainees learned how to handle the new tools and how to produce better quality products with a true finished luster on them. Drawing and cutting shapes, designing pendants, earrings or whole shell art was demonstrated. Half pearls (mabe) were also used for the carving exercises. Tokerau Jim demonstrated how to best utilize each shell, each mabe to reveal its best color and its real nature. Thanks to Tokerau Jim, they also learned how to incorporate traditional Tongan motifs in the carvings, making those products uniquely Tongan made.

One of the bottle necks of the handicraft activity is the lack of supply of mabes and pearl shells which limits the handicraft production. How can handicraft and mabe production be improved given the current state of the farming in Vava’u?

The need for spat 

Recently, pearl farmers from Vava’u (regrouped under the Pearl Grower association -PGA) have only been growing a limited number of shells using natural spat collection. Also, this poor recruitment of spat has resulted in the harvesting of adult oysters from the wild, which has further impacted recruitment, and natural spat fall of Pteria penguin in Vava'u is now extremely limited. 

The ACIAR are funding a 2.5 years research project (FIS/2006/172) focusing on the developing of appropriate hatchery culture techniques for Pteria penguin and the use of hatchery-propagated oysters for pearl production. This project involves collaboration with SPC and links in with the SPC Pacific aquaculture program. It hopes to disseminate its results through SPC channels.   

Further development of the pearl industry in Tonga is hindered by a lack of knowledge of the culture requirements of Pteria penguin and methods for optimising pearl production from this species. For example, only one preliminary study has reported on hatchery or nursery culture of Pteria penguin (Beer , 1999) and, while limited information is available relating to half-pearl production from the related Pteria sterna (Acosta-Salmon et al. 2006), similar information is not yet available for Pteria penguin. Research is required to optimize culture methodology and pearl production from Pteria penguin as a basis for sustainable industry development. This ACIAR project will address the following major aspects:  

• Hatchery culture of Pteria penguin and optimization of hatchery culture techniques

• Nursery culture and grow-out; optimising culture techniques

• Half-pearl production and aspects effecting pearl quality (position, location, time)

• Investigation of round pearl production from Pteria penguin

• Training of Tonga Fisheries staff in culture methods and pearl production

• Training of farmers and members of the PGA  Production of high quality half-pearl from Pteria penguin in Tonga has been clearly demonstrated and existing pearl farming expertise in Tonga provides considerable opportunity for this project to have immediate impact.  

A successful spawning at SOPU Mariculture facilities 

In May 2008, the hatchery at SOPU was upgraded by Tonga Fisheries aquaculture staff,   assisted by Andrew Beer and Antoine Teitelbaum (SPC aquaculture officer). Several tanks were cleaned and prepared for larval rearing. A filtered water system was rigged up and a spawning set up (including heat shock set up) was put into place. All the hatchery equipment needed for spawning and larval rearing were recovered or purchased while a first batch of 30 adult Pteria penguin broodstock were being air freighted from Vava’u.

The first batch of oyster were successfully induced to spawn and larvae where put in incubation. A second batch of 30 more broodstock was induced a few days later and produced more than satisfactory number of eggs, allowing us to fully stock all the available tanks of the hatchery. The extra spawn was placed in outside raceways and those were fertilized using agricultural fertilizer, hoping to produce a natural bloom of microalgae.

The temperature requirement of most pearl oyster hangs between 26 and 29°C for larval rearing (Ellis et al, 2005). During the run, the water was as low as 20°C over night in the hatchery and so a heat exchanger system was put into place and aquarium heaters were also used which allowed water temperatures to be maintained between 26-30°C.

A large proportion of the microalgae required as a food for larvae was provided as a commercially available algal concentrate obtained from Reed Mariculture in the USA. The species used were Pavlova sp and T-ISO. The encouraging results indicate that algal concentrates may be of considerable benefit to hatcheries in the region by reducing the requirement to culture live micro-algae for larval pearl oyster culture. This would simplify hatchery production and reduce the nedd for specialized culture facilities and technical capacity.

More than 500,000 eyed larvae were placed into settlemnt tanks. When sample spat collectors from these tanks were inspected indicated two weeks later, large numbers of spat were observed. Spat collectors were transferred to an ocean based longline and spat will be harvested from them in September 2008.

Both the spawning and larval rearing run of Pteria penguin and the shell carving workshop complemented each other in the sense that they assisted in increasing the supply of spat, in high demand in Vava’u as well as improving the end products of the Tongan carved shell and mabe industry. In the near future this sustainable activity should gain in popularity and provide more alternative livelihood to the rural populations of Tonga.

Beer, A., 1999. Larval culture, spat collection and juvenile growth of the winged pearl oyster, Pteria penguin. World Aquaculture ’99. The Annual International Conference and Exposition of the World Aquaculture Society 26th April – 2nd May 1999, Sydney, Australia. Book of Abstracts, p. 63.

Hugo Ruiz-Rubio, Héctor Acosta-Salmón, Alex Olivera, Paul C. Southgate, Carlos Rangel-Dávalos. (2006) The influence of culture method and culture period on quality of half-pearls (‘mabé’) from the winged pearl oyster Pteria sterna, Gould, 1851 Aquaculture, Volume 254, Issues 1-4, 28, Pages 269-274

Ellis S., Wise D., Ellis E., Haws M., (2005). Hatchery Production methods for the Black-lip Pearl Oyster (Pinctada margaritifera) based on Existing Hatcheries and Experiences in Republic of the Marshall Islands and the Federated States of Micronesia.63pp.

Teitelbaum A., (2007) Pearl Oyster Products Jewelry Making Workshop June 26 – July 2, 2007 South Tarawa, Kiribati – SPC internal publication 16pp.