Commercial Fisheries of WA - Pearling
The Fishery
Western Australia has a valuable and successful pearling industry, worth around $200m annually, and is the world's top producer of prized silver- white South Sea pearls.
Wild pearl oysters are collected by divers in waters off the WA coast between Cape Leveque and Exmouth. They are seeded on the fishing grounds, allowed to recover for several months, then carefully transported to farms where the pearls are grown out.
The most sought-after species is the silver-lip pearl oyster Pinctada maxima, which produces the splendid silver-white South Sea pearl. Other species, producing pearls with different characteristics, are farmed on a much smaller scale.
Pearl oyster fishing has a lively history of boom and bust through the vagaries of weather, biology, fashion and technology. Oyster beds were heavily exploited in the late 19th century for mother-of-pearl shell, used mainly for buttons and inlay work, and naturally occurring pearls were an occasional bonus.
Australian and European vessel owners employed Aboriginal, Malay, then Japanese divers who were more proficient at depth and in full diving suits. Pearling took a heavy toll of crews and divers in earlier decades with hazards such as cyclones, marine predators and the bends (decompression sickness).
The industry crashed in the 1920s and 1930s following the introduction of plastics for buttons and decoration but this calamity reduced fishing pressure on the stocks of wild oysters and allowed a valuable resource to recover.
Development of efficient seeding practices heralded the beginning of the cultured pearl industry in the 1950s and today WA produces pearls regarded as the world's best.
Sixteen licensees harvest P. maxima oysters and most farms are on the WA coast between Exmouth and the WA/NT border, though oysters are also taken to farms near Darwin and to the Monte Bellos Islands. There is also increasing interest in the production of half pearls and smaller round pearls from other pearl oyster species - Pinctada albina, Pteria penguin and Pinctada margaritifera.
Skilled divers work from sophisticated pearling boats which act as both fishing boats and floating operating rooms where oysters can be seeded, though some companies use separate vessels for fishing and seeding. After seeding, oysters are placed on the sea-bed in panels, which are turned regularly over the next two or three months to aid the formation of round pearls.
They are then taken to farms, and usually held in panels suspended from long-lines. Shells are regularly cleaned of barnacles and other marine growth.
Oysters are about three years old when captured and pearls take another two years to grow to desirable size and quality.
The best oysters may be seeded several times, with each pearl being larger than its predecessor.
Pearl culturing techniques are practised in Indonesia, Malaysia and Thailand using P. maxima, though the same pearl quality has not been achieved. The limited availability and rarity of the Australian pearl results in high prices for these luxury jewels.
Production from the WA pearling industry based on P. maxima has steadily risen and value of production in 1997/98 was estimated to be worth $189 million.
Fishing Controls
Pearling is managed as a ‘gauntlet' fishery, to allow the oysters to be caught at the optimum size, 120-160 mm. Oysters over 160 mm are not generally suitable for round pearl production and are not usually taken. These large oysters form the basis of the breeding stock and management of the WA fishery by the quota system has kept breeding stock at healthy levels.
Output controls are used: licensees have strict quotas (the entire industry currently has an annual quota of 572 units, with the value of one unit normally 1,000 shells, though there may be annual variations), shells must be a minimum size of 120 mm, and collection zones are designated.
In 1992, producers were first allocated options (20,000 shells per licensee) for the use of hatchery-bred oysters to seed for round pearls.
The purpose of quotas is to ensure sustainability of wild stock and optimise value to the community by maintaining prices. The industry can also plan long-term operational and marketing strategies with an expectation of stability.
Pearls
Pearls are formed when an oyster coats any hard particle entering its shell with layers of lustrous nacre, a form of calcium carbonate.
The Japanese cold-water akoya oyster (P. fucata), smaller than the tropical P. maxima, produces pearls up to 9 mm in diameter. These are usually cultured using round nuclei, though natural, non-nucleated, irregularly-shaped pearls (called keshi or ‘poppy-seed' pearls) occur in all oyster species. Australian cultured pearls begin at 10 mm in diameter and occasionally grow to larger than 20 mm. South Sea pearls from WA dominate the high quality large pearl market.
Oysters are initially seeded with nuclei made from Mississippi mussel shell which has sufficient thickness to produce large round nuclei. A piece of mantle (the tissue which produces nacre) from another oyster is inserted with the bead into a surgically-created pocket in the animal's gonad.
In an oyster's last year of production, a half-round nucleus is often used to produce a blister pearl (called a ‘mabe') on the shell wall. Round pearls are normally used for necklace strands and while keshi can also be strung, they and mabe are generally set in jewellery.
Baroque (irregularly-shaped) pearls can also be of great size and beauty, though strongest demand is for round pearls.
The quality of the lustre, or light reflection capacity, is paramount in determining a pearl's worth.
A pearl's value is determined by size and ‘quality'; ‘quality' is the sum of its lustre, roundness, surface perfection and colour.
Natural colours of pearls vary widely, from the ‘black' pearl cultured in Tahiti and the Cook Islands using P. margaritifera oysters to the silver-white pearls from Australian P. maxima.
Research
The goal of research in the fishery is to achieve a full understanding of the dimension and nature of stock levels. An understanding of the status of the stock allows quotas to be fine-tuned to stock levels.
The provision of catch and fishing effort data by fishers is a requirement of a pearling licence. Since this is a quota fishery, monitoring is strict. Catch details are given using blocks of 10 x 10 nautical miles, then in sub-blocks of 5 x 5 nautical miles, to allow accurate analysis of oyster distribution, which is often patchy by nature.
Information is recorded for each dive during the season and forms the basis of management strategies for the fishery.
Research is conducted by both Government and industry. Current research by Fisheries Western Australia is examining the status of the breeding or ‘MOP'(mother-of-pearl) stocks. This includes stock surveys, natural mortality experiments, and estimation of fecundity in these stocks.
Research during the 1980s was directed toward establishing techniques for breeding pearl oysters in captivity. This was successful and there are now several pearl oyster hatcheries in WA. Following this, growth rates and recruitment were examined and the Department of Fisheries is now undertaking trials of a spat collection program (in conjunction with industry), in order to obtain annual measures of recruitment.
Industry research is mainly focused on improving pearl quality and improving diver safety.
A the Department of Fisheries program during 1995-97 studied growth of pearl oysters across the three zones of the fishery and attempted to establish a measure of recruitment within the fishery.
Markets
Because of the quota system and corresponding supply, the high prices paid for these difficult-to-produce pearls are maintained.
Most Australian pearls were sold to Japan and marketed as South Sea pearls, but sales are now also being made directly to the US, Hong Kong and Europe. Silver-white pearls are preferred by the Japanese, as they are considered most flattering to Asian skin tones, but rose, blue and golden pearls are popular in other markets.
Environmental Status
In Australia, most oysters live in areas remote from human and industrial pollution, though polluted waters are a problem in Japan. Many Australian oyster farms are in remote bays, where their lines and buoys present no obstruction to boat traffic. Oysters, like most shellfish, are sensitive to water quality and if stressed they produce poor quality pearls and become susceptible to disease.
At present, wild stocks are found in pristine areas of the State's north-west, which provides farm sites with the most fundamental environmental requirements; sheltered waters in case of cyclones, sufficient depth and good tidal flow to flush water around the oysters.
An independant report commissioned by the Pearl Producers Association in 1998 on the environmental impact of pearling (P. maxima) in Western Australia found that the industry in general was environmentally benign, producing a high value product with a minimum of environmental distruption.
Future Directions
Hatcheries are beginning to produce pearl oysters to even out variations in supply from the wild stock. However, cultivating the tiny spat through to a seeding-sized oyster of about three years old involves considerable costs and may limit the ability to replace wild-caught oysters.
Early assessments of hatchery-reared oysters are promising, and pearls harvested from hatchery animals are of good quality.
The collection of wild spat is an alternative to hatcheries. The spat settle out of the water on to artificial collectors which are left in the water for 11-12 months. The spat are then removed from the collectors and raised in nursery areas. Spat collection was practiced by some sections of the industry in the early to mid-1990s but breeding technology has now surpassed the need to use spat collectors so this practice has been reduced.
Pearling licencees are issued with hatchery options (i.e. they can use a specified number of oysters from a hatchery for round pearl production in addition to their wild quota). This measure is designed to encourage the development of, and interest in, new technology in the industry without destabilising production and possibly affecting pearl prices.
Increased availability of oysters may allow them to be used for training future technicians and development of improved husbandry techniques.
Future research will involve gaining further data on factors affecting recruitment of wild oysters, including breeding stock levels: these factors are mainly environmental conditions around the time of spawning and early settlement of spat.
Fishery Snapshot
- The WA pearl culture industry is Australia's most valuable fishery after the WA rock lobster fishery.
- Oyster beds off the WA coast provide the wild shell which produces the silver white South Sea Pearl, highly prized for its size and quality.
- Production of cultured pearls was established by the Japanese and although the industry is now dominated by Australian interests, Japan remains a major buyer of the pearls produced. Other major buyers include the USA, Hong Kong and Europe.
For an overview of the management, current and historical catch details for these fisheries please see the State of the Fisheries Report.
Glossary
| Baroque pearls | Irregularly-shaped pearls of reasonable size |
|---|---|
| Catch returns | Obligatory records kept by fishers giving details of their catch and fishing effort |
| Demersal | Found on or near the bottom of the sea |
| Long-lines | Moored lines which have buoys supporting them at regular intervals on the surface. Vertical drop-lines hang from the floating line and suspend panels of pearl oysters |
| Input controls | Controls on fishing to limit catches, e.g. size of boat and gear, seasonal closures, or limiting licences |
| Fishing effort | Amount of fishing occurring |
| Limited entry fishery | Access to fishing grounds is limited to licenced fishers only |
| Keshi | Small natural irregularly-shaped pearls ('poppyseed' in Japanese) |
| Mabe | A blister pearl produced by mounting a half-round nucleus on the wall of an oyster in its last year of production |
| Output controls | Controls directly limiting a catch e.g. quotas |
| Recruitment | Movement, either by migration or growth to legal size, of juveniles into the main fished stock |
| Seeding | Inserting a nucleus into an oyster, to form the basis of a pearl |
| Spat | The developmental stage at which shellfish larvae form shells and settle out of the water to attach themselves to reefs |
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