The Australian Pearling Industry 
and It's Pearls

Australia is the world’s major producer of white South Sea pearls, for during the 1998 season the tropical waters off northern Australia yielded ~ 60 per cent of total world production of these much desired and very valuable bead-nucleated cultured pearls. White South Sea pearls are large (>10 mm diameter) rounded, lustrous, white, silvery, cream, or golden pearls that are cultivated by man in the gold- and silver-lipped pearl oyster (Pinctada maxima) that is indigenous to the off-shore waters of northern Australia. Other white South Sea pearls produced by the Australian pearling industry include ‘accidental’ whole baroque keshi pearls, and cultured bead nucleated half pearls that are commonly termed mabés.

The white South Sea pearl is a comparative newcomer to Australia’s pearling industry, for the history of this primary industry stretches back for well over a century to the time when Australia was one of the major supplier of natural pearls to European and American markets.

History
Australia’s pearling industry began hundreds of years ago with aboriginals harvesting abundant shallow water pearl shell from waters of the north western coast of Western Australia. By the time of European settlement, the aboriginals had a well established trading network for pearl shell, both within Australia and with Makassan trepangers (collectors of sea-slugs) who, since the late 17th and early 18th centuries, visited northern Australia to trade with the indigenous inhabitants of this remote coastline.

Interestingly, in 1812 the first Australian pearls were discovered in Queensland waters by Captain William Campbell. The first recorded harvest of pearl shell from Paumoto Archipellago followed in 1814.

The history of Australia’s pearling industry is spread over the warm tropical waters that stretch across the top of Australia from Western Australia to Queensland.

Western Australia
In Western Australia, European interest in pearl shell developed in tandem with the cattle industry. Indeed, commercial pearling commenced in Western Australia in the early 1860s, soon after the first pastoralists arrived on the shores of Shark Bay, some 540 km north of Perth, and at Nickol Bay — a further 1,000 km to the north. These avaricious newcomers soon subjugated native pearl shell harvesters, and in the process destroyed their long established trading patterns.

From 1862 to mid 1868 local aborigines were coerced, without pay, into ‘dry shelling’ for Shark Bay Pinctada albina albina. These small bivalves yielded commercial amounts of ~ 3 mm, often irregularly shaped, yellowish pearls. To the north, the much larger Nickol Bay P. maxima also was harvested both for its mother-of-pearl (MOP) as well as for its much rarer lustrous silvery white pearls. While the value of pearl shell and pearls was higher at Nickol Bay, the Shark Bay shells, with their more abundant pearls, were more densely distributed and much easier to access. These somewhat forgettable activities represented the start of Australia' s pearling industry.

Due to rapid depletion of readily accessible shells, 'dry shellers' then were forced to wade up to their armpits into deeper waters in their search for shell. Within three years, harvesting of pearl shell moved into deeper waters - up to two kilometres off-shore - with six to eight aboriginal men and women being used to ‘naked dive’ for shell from larger boats. At that time, a fair days work for a 'naked diver' was considered to be the recovery of 10-25 pairs of shell at the average rate of a pair of shells per eight dives.

Depletion of the early pearling beds, due to over-exploitation that included the indiscriminate removal of immature and undersized 'chicken shell', soon forced the avaricious pearlers to move their shell gathering activities progressively northwards towards Roebuck Bay, on which modern Broome is now located. Consequently, by 1875 half the pearling fleet was located in the vicinity of Exmouth; with the remainder working above Cossack. The same pattern of exploitation followed: depletion of 'dry shell' beds, followed by depletion of beds that were accessible to 'naked diving' by indentured Malay divers.

One distinct technological advance, that was made at that time, was the successful introduction of hard hat diving to the Broome area by the famous English gem merchant, W.E. Streeter. This occurred in the mid 1880s, and followed Streeter's retirement from the London retail jewellery trade. Now living in Broome, Streeter begun to invest his time, effort, and money into pearling. In a short time this entrepreneur purchased several schooners to service fleets of smaller pearling luggers that cruised the waters off north western Australia in search for pearl shell and pearls. Indeed, by the time self government was granted to Western Australia, in 1890, Streeter had already acquired a pastoral property on the outskirts of Broome, has established a store and house in Broome, and owned one-eighth of the pearling fleet. Streeter, a pioneer of West Australian pearling, died in 1923

By the early 1890s the pearling industry had become depressed; due to the combination of decreasing world demand for pearl shell, continuing depletion of resources due to overfishing, and governmental closure of pearling beds. In spite of these set backs, the industry continued on a small scale until the First World War, after which prices of pearl shell collapsed until the industry was rescued economically by the American market that purchased >50 per cent of all shell harvested during the 1920s and 1930s. This recovery lasted until the Great Depression, when the market for pearl shell finally collapsed, as did the West Australian pearl fishery - courtesy of the invention and marketing of the plastic button.

The first Australian cultured pearls were grown by a Mr G.S. Streeter, in Roebuck Bay, during the 1890s. This attempt was not an economic success. However, it was the attempt by A.C. Gregory to cultivate pearls near Broome in the early 1920s, that led the Western Australian Government to amend the Pearling Act to prohibit production, selling, and even the possession of cultured pearls. This regrettable action allowed the Japanese to dominate the pearl culturing industry for the next half-century. Indeed, it was not until this Act was repealed in 1949 that - six years later in 1956 - the first successful Japanese-American-Australian cultured pearl farm commenced operations at Kuri Bay to the north of Broome. Progress was rapid, for by 1973 Kuri Bay was producing ~ 60 per cent of the world' s large white South Sea pearls.

Presently, sixteen commercial pearl cultivators are operating in West Australian waters. Of these cultivators the Paspaley and M.G. Kailis companies each own three individual companies.

Queensland
In Queensland waters pearl shell and their associated pearls were first harvested, in 1868, from the Torres Strait that separates Australia from Papua-New Guinea. Thursday Island soon became the pearling capital of Queensland. In a manner similar to that which occurred in Western Australia, rapid depletion of natural P. maxima had been reported by the mid 1880s. As a consequence, a large fleet of Torres Strait pearlers, led by James Clark, sailed for the West Australian pearling grounds in 1886. This led the then West Australian government to introduce repressive taxes to control the pearling activities of these ‘invaders’.

Unfortunately, the first twenty years of overfishing in Torres Strait and adjacent Cape York, and the uncontrolled harvesting of mature shell by Japanese cultivators between 1920 and 1930, so depleted natural stocks that today few P. maxima exist in this previously shell-rich region.

With respect to pearl cultivation, in 1890 Willian Saville-Kent began collecting live pearl oysters from Torres Strait - both for shell cultivation and pearl culture purposes. Unfortunately Saville-Kent's pioneering experiments, which had a significant influence on the development of Japan’s akoya pearl cultivation technology, ceased on his death in 1909.

It was not until the late 1950s that joint Japanese-Australian pearl cultivation operations were established in the Torres Strait. However, a further disaster - in the guise of the Oceanic Grandeur oil spill which occurred in 1970 - caused such massive mortality among both wild and cultivated pearl oysters that Queensland’s pearl culture industry was virtually eliminated.

In spite of some evidence of recent recoveries in stock numbers, presently there are less than fifteen pearl culture leases operating in Queensland waters. Interestingly, spat hatcheries have been established in three Queensland locations: Albany Island, Turtle Head, and Fitzroy Islands.

Northern Territory
The Northern Territory also has a long history of pearling, with records indicating the schooner Sree Pas Sair recovered pearl shell from Darwin Harbour in 1884. Darwin soon became the pearling capital of the Northern Territory. As the stocks of pearl shell were rapidly depleted from Darwin Harbour, pearling spread along the coast of Melville Island to Cape Keith.

The Western grounds, which were discovered near Bathurst Island around 1929-1930, were fished out by 1939. Some four decades later (1936), the Eastern grounds off Boucat Bay were discovered. However, by mid 1950 this fishery also was no longer commercially viable.

Presently, pearl culture operations in the Northern Territory are centred on the Coburg Peninsula, to the north-west of Darwin. Pearl cultivation also occurs in Darwin and Bynoe Harbours.

White South Sea Pearls
The value of world cultured pearl production during 1998 has been estimated to be Japanese akoya (US$180 million), Chinese akoya (US$25 million), white South Sea (US$220 million), black South Sea (US$150). World production of white South Sea cultured pearls for the 1998 season was 650 kan (2437.5 kg or ~2.5 tonnes). This contrasts strongly with world production in 1936, which was a mere 5 kan (18.75 kg).

The Product
Australia is the world’s largest producer of white South Sea pearls — that is, bead nucleated cultured pearls of more than 10 mm diameter that have been grown in the gold- or silver-lip pearl oyster Pinctada maxima. Australian white South Sea pearls have an average diameter of 12-14 mm, however diameters may range from 10 to an exceptional 20 mm. While the less than 8 mm diameter Japanese akoya cultured pearls may have a coating of nacre of ~0.4 mm thickness, an average 15 mm Australian South Sea pearl has nacre thickness of 4 mm - and a superior lustre and orient to match.

Australian production of 415 kan in 1998 represented 65 per cent of world production. This production was based on an annual government-controlled quota of 577,000 wild shells, and part of the quota of 350,000 hatchery-bred shells. Sixteen companies, most from Western Australia, operate pearl farms.

Other essential products of Australia’s white South Sea cultured pearl industry include half-pearls up to 25 mm diameter, that are available in a range of shapes, and an intriguing range of designer-ready baroque accidents — termed keshi pearls in the trade.

The Industry
Australia’s pearl culturing industry commenced in 1965 when Pearls Proprietary Ltd established a pearl culture farm at Kuri Bay, some 420 km north of Broome, Western Australia

By 1963 this farm was producing 60 per cent of the world’s finest white South Sea pearls. Presently, the high quality product from farms operating in Western Australia (centred on Broome), and in the Northern Territory (around the Coburg Peninsula and in Darwin and Bynoe Harbours) dominate the burgeoning Australian white cultured pearl industry. A few Queensland-based pearl cultivators, who operate in Torres Strait at several locations down the eastern seaboard of Cape York as far south as Cooktown, are presently minor contributors to Australia’s overall production of white South Sea pearls.

Presently, the legal quota of oysters that can be harvested for implantation in Western Australia includes 575,000 wild oysters from off shore beds (now reduced to 500,000) and 350,000 hatchery-reared oysters (the majority of which are not yet in production). Because areas suitable for pearl cultivation are limited, new leases are difficult to obtain, and the annual quote of wild oysters is unlikely to increase, quality rather than quantity of Australian white South Sea pearls should increase over the next few years.

Most Australian pearl cultivators believe that careful management of natural oyster stocks is essential to ensure that these remain self-sustaining at present levels of annual harvesting. They express continuing concerns that the costs, risks and quality of pearls obtained by implanting hatchery-reared oysters are not favourable. Thus, full use of this resource is not expected for some years.

In Australia, the Darwin-based Paspaley group is the major producer of white South Sea pearls. This vertically structured cultivator produces more than fifty per cent of Australia’s total crop of white South Sea pearls.

Modern Australian Pearl Culture Technology
Cultivating round South Sea pearls
In Australian waters, wild ‘shell’ of >120 mm dorso-ventral shell length are collected by teams of up to six divers from offshore shell beds that stretch from Exmouth Gulf in the south to the Lacepede Islands in the north of Western Australia, from Northern Territory’s eastern grounds along the Arnhem Land coast between Golburn and Crocodile Islands, and to the west of Badu Island in Torres Strait, Queensland. Up to 10 dives per day are undertaken by these divers.

To collect shell, hookah-equipped divers are towed underwater behind boats, which drift with the current. Once collected, the wild shell is cleaned, inspected, and stored in net panels of 6 or 8 shells that are tied onto longlines which are moored to the bottom of the seabed to create ‘dump sites’. In the past wild shell were transported from these ‘dumps’ to farms, where seeding was performed.

Today, most West Australian cultivators significantly reduce mortality rates, that used to occur as a consequence of this transfer, by seeding wild shell (in mid-year) at the collecting grounds — using large modern ships that are equipped with surgically clean laboratory and operating facilities. On the ship mostly Japanese-trained technicians implant each wild shell, in the traditional manner, with a round nucleus and a small piece of mantle tissue from a ‘sacrificial’ oyster. The nuclei, which are manufactured from thick shell of the fresh water Mississippi mussel, can have a diameter of from 6.6 to 14 mm — depending on the size of the shell to be implanted, and whether or not the shell had been previously implanted. During the season technicians each operate on 550-600 shells per day, using sterile surgical conditions and dexterous surgical technique.

Following seeding, the implanted shells are returned to net panels on bottom longlines moored at ‘dump’ sites. Here they remain for up to three months, during which time they are inspected and turned regularly by divers to ensure that an even envelope of nacre secreting cells forms a sac around the nucleus. After this stage has been completed, the net panels are retrieved (during the warm October-December months) and the implanted shell are very carefully transported by boat to pearl farm growout sites in well protected coastal bays and inlets.

During growout, the implanted shell may be held in net panels either on well protected less expensive-to-operate surface longlines (e.g. Western Australia and Northern Territory), or bottom posts and longlines, about 13 m down - where the shell is less vulnerable to cyclonic conditions, but does require continuing maintenance by underwater divers (e.g. Western Australia). Net panels can be held either on individual posts, or on underwater ‘fences’. During the two-year culture period of growout, implanted shells are cleaned every two to four weeks — either by underwater divers, or by boat-mounted high pressure cleaning machines. Four to six months after seeding an X-ray checks each shell for nucleus retention and pearl formation. Shell that have rejected nuclei are held until the following year. At that time they are re-seeded if they are healthy and have little scarring from the previous attempted seeding. Re-seeding will not occur if shells have commenced forming keshi pearls as a consequence of the tissue implant grafting into the incision and forming a pearl-producing pearl sac.

Typical Work Schedule for an Australian Pearl Farm

January - Prepare for wild shell collection, organise dive crews, fishing gear,
paperwork and licence fees.
February - Fishing for 20,000 wild shell begins, linked to tide charts.
(Note: Tides in the area can vary by 10 m per day.)
March - Collected shell is ‘dumped’ on the seabed on site owned or leased by the company and allowed to rest. Maintenance of dumped shells, turning and cleaning them. X-ray shells seeded last year to check if implanted nuclei have been rejected. Oysters that reject nuclei are usually re-seeded.
April - Water temperature begins to drop as winter approaches, rest period for the shells.
May - Ongoing farm work, turning and cleaning previous two year’s seeded oysters kept suspended in wire panels in the water column.
June - Prepare for operating on oysters to implant nuclei. (Note: Some technicians may come from overseas, and some companies have boats fitted as mobile laboratories so seeding can be done on the pearling grounds.) Seeding and harvesting begin.
July - Normal operating time for pearls, seeding new oyster, re-seeding those which have rejected nuclei. Oysters that produce acceptable pearls are also re-seeded.
August - Harvest of previous year's seeded shell continues, then a two-month turning program follows operations. The oysters are turned over to encourage production of round pearls.
September - Turning operated shell.
October - Turning, cleaning and change of areas.
November - Transportation of operated shell to grow-out areas.
December - Dump and clean gear.

Pearls are harvested in the cooler winter months, after about two years of cultivation. This time is deliberately chosen, for in the winter months nacre secretion is slower, more uniform, and the nacre has peak lustre. Also the lower temperatures seem to reduce stress and consequent mortality in the shells.

At harvest the pearls are categorised into saleable bead nucleated pearls, rejects, and keshis. It is important to remember that today there is a growing market for designer-friendly natural pearl look-alike baroque all-nacre Australian keshis.

Presently, the overall mortality rate for seeded shell, over the two-year cultivation period, is a mere 5 per cent. When to this mortality is added the 4 per cent of molluscs that must be sacrificed to yield the siabou (nacre-secreting graft ) tissue, a 3-5 per cent post operation mortality, and a 20 per cent rate of nuclei rejection; this leaves approximately 66 per cent of implanted shell healthy enough to form pearls.

The yield of good quality pearls usually determines that about 60 per cent of shell that contained a saleable pearl will be reseeded - this time with a nucleus the same size as that of the pearl that was removed. The reason for less shell being reseeded, irrespective of producing a saleable first crop pearl, is simply that as the reseeded pearl is likely to be of lesser quality than the original pearl only shells capable of producing a good quality first crop pearls are reseeded. The shell is then cultivated for a further two years, with about 40 per cent of implanted shells that remain following mortality and nucleus rejection being suitable for implantation with a third nucleus and so being capable of yielding 17-19 mm pearls. Indeed, up to four pearls have been produced from a single shell before it was considered unsuitable for round pearl production.

Typical harvest results claimed for West Australian white South Sea pearl production include: first extraction, ~85 per cent saleable with an average weight of ~16.5 ct; second extraction, ~65 per cent saleable with an average weight of between 21.5 and 23 ct; while the third extraction produces a variable yield of large size pearls.

Each day’s harvest is initially sorted and graded into categories of colour, size, and shape by shipboard implantation technicians. The reason is quite simple, for the financial reward of these technicians often is tied to the productivity of his or her implanted shells.

The pearls are then transported to the company’s headquarters, where they are carefully cleaned of residual mucus or salt, before the better quality pearls are gently tumbled with a mild abrasive, such as cooking salt, to remove any adherent organic material (dried mucus) and thus optimise the lustre and orient of the pearls. Lower grade pearls are only tumbled in finely ground pumice to enhance smoothness; for South Sea pearls are not colour-enhanced in any way by bleaching and/or dyeing.

Following cleaning, the pearls are sized, classified, and graded ready for sale to world markets.

Cultivating mabé pearls
Once a pearl oyster is deemed to be incapable of producing further round pearls it is used for half-pearl production. Following the gluing of suitably shaped plastic nuclei onto the insides of both valves, the shell is cultivated for a further 10-12 months. At harvest, the shell is killed and its nacreous blisters trephined from valves for manufacture into half-pearls.

Artificial spat culture in Australia
In Australia, the success of hatchery-bred shell has been limited; but is improving with refinements of hatchery technology. Basic steps in the hatchery breeding of P. maxima spat are:

• Selection and growth of a suitable algal culture to support optimal growth of spat.
• Selection of suitable breeding stock.
• Controlled spawning.
• Laval culturing.
• Laval settling.
• Planting and growout

The basis of the lucrative South-sea pearl industry the silver- or gold-lipped pearl oyster, Pinctada maxima, begins life with the odds well stacked against its survival. As the oyster matures it generally begins its reproductive life as a male and may change, sex to female later in life. The switch from male to female, and even back again, is triggered by environmental conditions. Excellent conditions in terms of food availability and water quality will favour development of females, whilst adverse conditions tend to favour males. In the wild the sex ratio of male to female is roughly equal in oysters larger than 15 cm (greater than two years of age); however, on the farm there are considerably more males than females — probably as a result of regular disturbance during cleaning and other farm activities.

Pearl oysters spawn as a result of external stimuli such as rising water temperature or changes in salinity. In the hatchery spawning may be induced by increasing the water temperature in the holding tanks. Generally, males spawn before females. The release of sperm into the water stimulates spawning in ‘ripe’ females. Unfertilised eggs or ova are released in enormous numbers, a single female may release up to 50 million eggs! The eggs are initially pear shaped and become spherical following fertilisation. Fertilisation in the wild is haphazard and will only occur where sperm and egg are united. In the vast bays and oceans that silver-lipped pearl oysters populate, the chances of successful fertilisation are small. In the hatchery fertilisation can be controlled due to small water volume and the close proximity of spawning males and females.

The division of cells after fertilisation is rapid; and within 24 hours the newly developed larvae have a functional stomach and are able to swim. At this early stage they are called "D" or straight hinge larvae. A week later, the larvae begin to change shape and become more rounded. They are now at the umbo stage of life. At this time they are only 0.1 mm in size, but appear very much like a cockle or pipi when viewed under a microscope. At between 16 and 20 days of age they will develop two red pigment spots called ‘eye-spots’. These eye-spots are light sensitive. Within a few days the larvae will begin to develop a foot which is used to crawl snail-like on surfaces in order to search out appropriate place to settle. At this stage the larvae are called pediveligers and are about of 0.2 - 0.3 mm size. In the hatchery specially prepared rope panels, or collectors, are placed in the culture tanks to ‘catch’ settling larvae.

The first stage of settlement occurs when the pediveliger secretes hair like fibres (the byssus) from its fool The byssal fibres adhere to the surfaces of collectors or other objects in the water. Once firmly attached, the pediveligers will begin to metamorphose. This is a traumatic time and many of these larvae will not survive. During the three or four days following settlement larvae lose the ability to swim, and many of the organs that have served them during the early part of their lives are resorbed … and new organs, such as gills, rapidly develop. The larval shell takes on a new shape and growth is very rapid. With the development of its new shell, the ‘oyster’ is now called a plantigrade, and within a few days of settlement is already nearing a millimetre in size. The plantigrade stage only lasts a few days before the small oyster becomes a spat. The spat look much lace the adult oyster but come in a multitude of colours that include yellow, brown, black, green and white. A prominent feature of young spat are the ‘finger-like’ growth processes that they have along the edge of their shells. Over the next twelve months growth of spat is rapid and most oysters will have reached 10 cm sizes during their first year of life.

Between 18 months and two years the silver- or gold-lipped pearl oysters reach maturity - and the cycle of reproduction and growth can begin once more.

To date the greatest problem experienced with Australian-produced hatchery shell occurs when the spat are transferred from the hatchery to the ocean based pearl farms for growout.

To Australian producers, the downside of increasing reliability on hatchery-bred stock is:

• Farmsites suitable for hatchery grow-out are limited.
• The overall costs of utilising hatchery-bred stock are much greater.
• Hatcheries must be licensed and all oysters must be inspected by government marine biologists before they are released for grow-out.
• The financial return from hatchery-bred stock is much longer — >5 years for smaller pearls and up to 7 years for larger diameter pearls. Most of the additional cost comes from the 2 year grow-out period required before these oysters are ready for implantation.
• The size of pearls recovered are usually smaller, as it is much more economic to utilise younger and therefore smaller oysters for implantation. The largest pearls obtained from hatchery-bred stock are 14 mm. Overall, sizes range from 10-11 mm.
• The yield of round pearls from hatchery-bred stock is lower (~ 20 per cent) than with wild oysters, for most pearls are off-round and baroque. Drop shapes are a little more common than round pearls.
• Yield of valuable colours (particularly golden pearls) tends to be reduced.

Although each Australian producer is allowed to seed 20,000 hatchery-bred oysters annually, only 70,000 shells were seeded during 1997. By 2002 this agreement will cease, with producers not establishing spat-breeding technology loosing their quota. It has been estimated that it will take a further 10 years before all Australian producers adopt hatchery-bred stock.

Factually, over the last decade many Australian pearl cultivators who have implemented hatchery shell development are experiencing mixed success with the development of the necessary ocean based husbandry skills essential for successful growout to maturity. Although the future use of hatchery bred shell undoubtedly will increase in the Australian industry, from its current low levels of utilisation, industry leaders remain firmly convinced that wild shell yields better quality and superior colours than that produced by hatchery-grown shell.

Current Australian Production
Total production of South Sea pearls (excluding low grade pearls unsuitable for jewellery) by Australia’s 16 major producers was 350 kan for 1997, and estimated to reach 400 kan (1,500 kg) for 1998. Since 1987 production has increased at an average yearly rate of 8 per cent. More importantly, the size of pearls produced has been increasing more significantly that their quantity. Production, which is presently controlled by an annual government quota of harvested wild oysters, is expected to increase further as more use is made of use of hatchery-grown stock.

Reference:

• O’Sullivan, D. (1995) Pearls of Australia: An overview of pearl production techniques in Australia. Australian Gemmologist. 19, 155-161.
• Rose, R.A. & Baker, S.B. (1989) Research and development of hatchery and nursery culture for the pearl oyster. West Australian Marine Research laboratories FIRTA Project 87/82. Final report. Perth. 26pp.
• Taylor, J. (1997-1999) In Atlas-Pacific Ltd’s Reports to shareholders Nos 1-9.

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