The main focus of the pearling industry in Western Australia is the South Sea pearl, produced by the pearl oyster Pinctada maxima.
The P. maxima commercial fishery is managed under the Pearling Act 1990, regulations and Ministerial guidelines.
A licence is required to fish for wild stock P. maxima. However, the fishery is a ‘limited-entry’ fishery, meaning no new licences are being issued.
A licence or permit is also required to establish a pearl farm or hatchery.
The quota system
The fishery is primarily managed using a quota system that sets a maximum number of wild stock pearl oysters that can be caught each year by the 14 licence holders.
Researchers set the quota at a level that ensures stocks are sustainable. We closely monitor the quota through placing observers on pearling vessels and sophisticated stock assessment research.
Controls take the form of a total allowable catch (TAC), which ranges from 500,000 pearl oysters to 1.5 million in a good year. The TAC is divided into individual transferable quotas (ITQs). We review wild stocks each year then set the TAC for each of the three pearl oyster fishing zones.
Hatchery-bred pearl oysters are now a major part of pearl production. The value of a hatchery quota unit stays the same but the value of wild stock quota units varies – in some seasons high wild stock levels means higher quotas.
Generally, pearl divers are not allowed to collect pearl oysters unless they are a minimum size of 120 mm in shell length.
However for the 2012 and 2013 fishing seasons, pearl divers are permitted to take a sustainable amount of pearl oysters of a size no less than 100 mm, on a trial basis, for research purposes.
There are also zone-specific maximum legal sizes, where appropriate.
Surviving the ‘gauntlet’
Young, fast-growing oysters (mostly males) of 120-165 mm are targeted by divers for their pearl-producing qualities. They are fished for three to four years before growing to a size where they are no longer suitable for the purpose of pearl production.
We use a ‘gauntlet’ fishing strategy, with many pearl oysters not collected, largely because a portion of the stock is protected through TAC limits. If those pearl oysters survive the ‘gauntlet’ of being collected at three years of age and keep being missed until they’re six years of age, they are then too big to collect for pearl production.
Those that survive the ‘gauntlet’ can live for another 15 to 20 years, or more. Together with very low natural mortalities, this creates a large breeding stock.
The broodstock is also boosted by pearl oysters in deeper water that are not gathered by divers.