KMRS - Science of Pearls

The science of pearls; the Silver-lipped pearl oyster Pinctada maxima

Pearl Oysters & Aquaculture

Molluscs represent 23% of all named marine species and comprise over 100,000 identified species of (primarily) marine invertebrates. Within this phylum, only a limited number of bivalve and gastropod molluscs produce the chemical substance that creates pearls. This substance, called “nacre”, consists of layers of hexagonal “aragonite” calcium carbonate bound together by an organic protein membrane. Pearls are created as a result of misplaced nacre-producing mantle cells which are found in the outermost epithelium of the mantle tissue that lies against the shell. The Silver-lipped pearl oyster, Pinctada maxima, is the world’s largest pearl oyster and subsequently produces the most exquisite, large and valuable pearls; Australian South Sea Pearls.

Modern pearl culture in Australia involves both wild and hatchery spawned oysters, commonly referred to simply as shell. At Cygnet Bay Pearls, wild shell is collected from the only wild fishery for pearl oysters in the world at Eighty Mile Beach, 250 nautical miles south of Cygnet Bay. Particular size limits and quotas apply to this fishery and, once transported by sea to the farm lease, shell can be seeded to start the culturing process following a brief resting period. Simultaneously, hatchery spawned juvenile oysters or “spat” are reared in our hatchery tanks in Broome before being transported to nursery grounds within the Cygnet Bay farm lease where the shell is nurtured as it grows to seeding size.

To seed an oyster for pearl culture, 3 shells are involved;

1) Nucleus shell made of Mississippi clam shell or mother-of-pearl

2) Donor shell with good lustre, used for nacre-producing mantle tissue grafts

3) Husbandry shell in which the nucleus and mantle graft will be inserted for pearl cultivation

Today, pearling aquaculture operations such as ours at Cygnet Bay Pearls involve years of care and maintenance to nurture oysters towards creating each and every pearl harvested. At a minimum, each oyster takes 2 years to create a single pearl. During these 2 years, the shell are stored in panels suspended from longlines in the nutrient rich, high flow waters of Cygnet Bay. Shell are cleaned and turned monthly to avoid excess biofouling, periodically scanned on our x-ray barge to assess pearl development, and moved throughout different areas of the farm lease to conditions which best suit the size and developmental stage of the shell.

At Cygnet Bay Pearls, we currently have 250,000 Silver-lipped pearl oysters (Pinctada maxima) in various life stages throughout the farm lease; from hatchery reared baby “spat” shell in their first weeks of existence to mature 8 year-old shell producing their 3rd commercially valuable pearl. Our seeding technicians currently have a 95% success rate in culturing fine quality pearls in each oyster they operate on.

In the quest to culture the only gems created by living creatures, pearl aquaculture represents both a science and an art. Natural unpredictability across all phases of the culturing process reflects the dynamic nature of the marine environment our pearl oysters inhabit. Thus, the nutrient rich, pristine Kimberley waters in which Cygnet Bay pearls are harvested are our most valuable asset and monitoring their condition continues to form an integral part of our operations and management as it has done for the past 65 years.

To find out more about how our pearls are cultured, please visit our Cygnet Bay Pearls website.

To hear a radio interivew with James Brown on the history of the family and the farm, check out this link to the University of Technology Sydney radio site A Question of Balance.