Blue Pearl 3
Culturing Abalone Half Pearls

Blue pearl 3, the story of New Zealand Eyris Pearl™

by Pam Hutchins FGAA
Wide Bay Valuation Services, Bundaberg

(Used with Permission)
Thanks, Pam, for suggesting that I add your informative paper to
Part 3

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‘Wild’ abalone are harvested from designated areas where they are most active and prolific. Special non-injurious tools are used to prize the abalone from their underwater rocky substrates without damaging either their shells or delicate soft tissues. A special slightly curved plastic tool is used to slip under the front of the abalone. To avoid damage it is important that divers be aware of which end to lift the abalone from the rocky surface to which it is firmly attached. This specially designed plastic lifter will neither harm the animal nor damage the flesh of the animal and so cause it to bleed to death (as abalone are haemophiliacs = bleeders). Special tool for removing abalone from rocks.

It takes about 3 years before the abalone reaches adulthood. At this stage, adults are tagged with a notch on the shell and a red tag cemented to the outside of the shell.

When the harvested abalone are brought to the surface, they must be stacked carefully so that they do not stick together (by their muscular feet). If this occurs, this causes great problems for those attempting to separating them.

The pearl farm

The long-term health of captive abalone is affected by a variety of factors that are related to the seawater in which the abalone are kept. These factors include the chemical composition, temperature, pH, oxygen and nitrogen levels, and flow rate of the seawater. All of these factors play an important part in the health and growth of the abalone, and of course, the ability of the abalone to produced quality nacreous pearls.

Efficient farm management requires the systematic monitoring levels of these factors in the water associated with the farm site, and the gathering and dissemination of this information to local and regional councils so that these regulatory bodies are aware of and can monitor any environment issues that may develop.

If the water temperature fluctuates greatly between 6 and 21°C, then this will affect the colour of the nacre that the abalone will secrete; it will determine the layering of both conchyolin and nacre; and will modify the intensity of colour in the secreted nacre. This well illustrated Akaroa Harbour, a harbour that has highest rise and fall of sea water temperature of any pearl culture site in New Zealand.

All cool water abalones are slow growing and can live up to 6 years of age if predators or disease do not kill them first. To improve the survival rates of their implanted abalone, Eyris Blue Pearls use specially design barrels to house the abalone involved in their pearl culture. These barrels (Fig. 8) are manufactured from black, medium density polyurethane plastic which resists the growth of fungus on its surfaces. Each barrel has plastic mesh its top and bottom, and flow-through mesh vents in its sides. The inside of each barrel is divided into four sections in which the abalone are housed and are free to move around within a relatively restricted area. If sea snails enter barrels containing abalone, these snails will remove any adherent sponges that may start to grow on the abalone and so threaten their health.

Abalone farming barrel

Fig. 8. A UV stabilized medium density polyurethane barrel, with water circulation vents, in which abalone are kept during pearl culture. Each barrel is specially conditioned, before paua are housed in them, by soaking the barrels in seawater for one month. This removes the plastic taste from the barrel, as abalone can not be housed successfully in new unconditioned barrels.
Blue Pearl 3

Good hygiene is very important if the abalone confined to these barrels are to maintain health and nacre secreting ability. Consequently, the abalone must be regularly removed from their barrels, their shells hand scrubbed to remove contaminants and parasites, and then checked for any infections--while the barrels are being cleaned by high pressure sea water to remove any debris, or adherent seaweed and other sea life.

While secured in these barrels, the implanted abalone will continue to spawn, with their fertilized larvae floating away to hopefully settle, grow naturally, and naturally Reseed the area in which the barrels are located. If this natural spawning tends to be irregular, then the farm often will introduce some peroxide into the water to stimulate the spawning of the abalone naturally.

The nucleation process

As some parts of this process are kept as closely guarded One month before the nucleation operation is due, ‘wild’ abalone of legal size are harvested by free divers. As the New Zealand Government has placed a quota system (bag limit) on the number of abalone that may be taken from the wild each year, each farm has to operate within the constraints imposed by this conservation-based system. This quota system prevents over fishing of the abalone. Abalone divers are specially trained so that they minimize injury to the abalone during capture and removal from their natural habitat. Following capture, the abalone are brought to the surface and placed in plastic barrels in a suitable holding area. The paua are nucleated on board a specially developed pearling vessel.

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At the time of implant, the now-acclimatized abalone are removed from its holding barrels and a small hole or a series of small holes must be atraumatically drilled through the shell of each abalone to facilitate placement of a pegged implant under the mantle of the abalone. During this implant operation care must be exercised to ensure that the soft tissues of the abalone are not damaged in any way--for abalone are hemophiliacs and will bleed to death if cut.

Nucleation Blue Pearls
Fig. 9. Retraction of the body and mantle
of the abalone to allow the pegged implant
to be inserted in a hole drilled through
the shell of the abalone.

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The implants, which are of proprietary design, are manufactured from moulded white plastic. They have a somewhat flattened hemispherical shape, diameters of from 8-14 mm, smooth outlines, a retaining peg projecting from the base of the implant, and they must have no projections or rough areas that can injure the mantle tissues of the abalone. No adhesive is used to maintain the implant in the shell.

Two implant locations seem to be used: one located around the periphery of the abalone’s shell and a second located deep within the shell near the shell’s internal whorl.

Attached Abalone
Fig. 10. Implanted abalone
attached to the wall of a culture
barrel for grow-out.

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Once the implant operation is completed, the ‘mother’ abalone are returned to their culture barrels (Fig. 10). Each barrel is given a number and a record is kept of the number of implanted abalone contained in each barrel.

Unlike pearl ‘oysters’, each abalone can only be nucleated once. One to five beads are nucleated in each abalone, depending on its size. Sizes of cultured half-pearls yielded after an appropriate grow-out period range from diameters of 6 –20 mm.

Matt white Bay
Fig. 11. On the pearl farm in Matt White Bay
on the Banks Peninsula the culture barrels
are suspended under water from ropes
suspended from buoys in waters with good
tidal flow.

Blue Pearl 3

Eyris cultured half-pearls are farmed (grown out) for a minimum of two winters and two summers in black high density polythene barrels that are suspended from long-lines off shore (Fig. 11). During the time of grow-out the abalone must be regularly fed with a proprietary mix of freshly harvested seaweed. Its is a fact that the abalone are very fussy and are indeed gourmet eaters, for they like to eat seaweed that humans also find tasty and palatable.

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Seaweed that produce the best display of colours in abalone nacre include an appropriate mix of:

• Macrocystis pyritera or giant kelp (Fig. 12A)--a large brown seaweed that has big leaves and a bulky, slightly coarse texture,

• Gracillaria (Fig. 12B), a fine filamentous red seaweed that has a fine texture, and

• Ulva, or green seaweed

Giant kelpRed Seaweed
Fig. 12. Seaweed suitable for feeding
implanted abalone.
A – giant kelp, B – red seaweed

Blue Pearl 3

The implanted abalone will consume up to 50 per cent of their body weight of seaweed each week, with their mix of food varying from week to week. Together with water temperature, pH and salinity of the seawater, it is the composition of mix of seaweed that is fed to the implanted abalone that determines the quality and iridescence of nacre secreted by the abalone.

To maintain a constant supply of the seaweed, this must be collected from the shorelines after a big storm, or deliberately harvested from kelp farms. Collecting shore-washed seaweed means that at that time ‘all hands must be on deck’ to collect seaweed, cut it into appropriate sizes, and then freeze or dry it for later use when no shore-washed seaweed is available for collection. Dried or frozen is simply rejuvenated by immersing it in fresh seawater. This rapidly brings back the shape and bulkiness of the kelp.

Some fine seaweed that grows on the culture barrels is also harvested and fed to the implanted abalone. With respect to abalone pearl culture it is important to remember that without reliable supply of quality seaweed, pearl farming would not be a viable operation.

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