10 abalone culture 8 allsopp2011

8

Abalone Culture

Mark Allsopp, Fabiola Lafarga-De la Cruz,
Roberto Flores-Aguilar and Ellie Watts

8.1 INTRODUCTION
Abalone is a prized seafood delicacy worldwide. Abalone are marine gastropod molluscs
of the family Haliotidae, also called sea snails, ear-shells or sea ears. They possess a single
shell, which is a low open spiral structure, and a large muscular foot that is used to attach
to hard surfaces. The family Haliotidae contains one genus, Haliotis, and about 100 species
are recognised worldwide (Jia & Chen 2001). More information on the biology of abalone
can be found in Jia and Chen (2001).
Aquaculture activities have grown considerably in the past decade, increasing their
contribution to the global market as fisheries continue to decline worldwide. Abalone
aquaculture industry has rapidly developed from about 3,000 tons in 2000 to over 40,000
tons in 2008 (FAO 2010). The principal countries producing cultured abalone are China,
Korea and Taiwan. Several other countries including Australia, Chile, Mexico, New
Zealand, South Africa, Thailand and the United States are also developing abalone aquaculture industries. With the maturity of production lines from farms worldwide the industry
has established markets in mainland China through Hong Kong, Japan and Singapore. The
demand for cocktail-size abalone has driven the expansion and development of the industry
throughout the producer countries. A variety of abalone species are cultivated around the
world (see Table 8.1).

8.2

THE ABALONE MARKET

The two largest consumers of wild and cultivated abalone are China and Japan. Generally
the Chinese prefer a lighter coloured ‘foot’ and the Japanese a darker one; a characteristic

Recent Advances and New Species in Aquaculture, First Edition. Edited by Ravi K. Fotedar, Bruce F. Phillips.
© 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.


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Table 8.1 Abalone species cultivated around the world.
Country

Commonly cultivated species

Australia
New Zealand
China and Taiwan
Taiwan
Korea

Haliotis laevigata and Haliotis rubra
Haliotis iris and Haliotis australis
Haliotis discus hannai
Haliotis diversicolor
Haliotis discus, Haliotis discus hannai,
Haliotis diversicolor, Haliotis
diversicolor supertexta
Haliotis discus hannai
Haliotis asinina
Haliotis midae

Haliotis discus hannai, Haliotis
rufescens
Haliotis rufescens, Haliotis fulgens,
Haliotis corrugata
Haliotis rufescens, Haliotis fulgens,
Haliotis corrugata
Haliotis kamtschatkana
Haliotis tuberculata

Japan
Thailand
South Africa and Namibia
Chile
Mexico
USA
Canada
Ireland

Production 2008* (tons)
504
8
33,010
348
5,146

NA
30
1,040
515
60

175
NA
NA

Note: NA = No data available
* Production data obtained from FAO Fisheries and Aquaculture Information and Statistics Service website

that varies between species. The preferred size category is between 200 and 300 g per
abalone, but most cultivated abalone are sold at between 50 and 150 g.

8.2.1

Japan

Japan is the largest world consumer of live, fresh and frozen abalone. These product forms
are generally identified as having the highest premium on the world market. Because Japan
is the largest consumer of premium-quality abalone, Japanese consumer preferences are
important in understanding the premium abalone markets. The Japanese native fishery is
historically significant and highly valued as a cultural resource. It has given rise to cultural
traditions and consumer tastes that make the appearance of an abalone as important as taste
and texture when determining the value of the product (Oakes & Ponte 1996).

8.2.2

Mainland China

Mainland China is the largest consumer of abalone, a fact that often remains unrecognised
because consumption of abalone in China is almost entirely in the canned form. In regions
such as Japan and the USA, canned abalone is generally not considered a premium product.
Canned abalone has a traditional place in Chinese society as an item of prestige, often

presented as a show of affluence or a demonstration of respect. Considered customary in
banquets and traditional feasts, a single can of abalone is often given as a token of respect.
The strong traditions surrounding abalone consumption in China have created a stratified
market, based on perceived quality differences between popular brand names and countries
of origin. The major distribution point for canned abalone destined for mainland China is
through Hong Kong (Oakes & Ponte 1996).


Abalone Culture

8.2.3

233

USA

In the USA there is a traditional market for abalone, which is mainly in California, where
there was a flourishing fishery until the early 1970s. In the California market tradition,
abalone are removed from the shell and sliced into steaks, which are tenderised and then
fried. At one time in California, abalone was an abundant, low-cost regional delicacy, but
as the fishery dwindled due to over-harvest, constricting supplies caused the market price
to increase to a level that has severely restricted demand for the product. The traditional
US market now consists primarily of expensive, white tablecloth restaurants in California.
The emergence of Asian communities as a significant abalone market in major US metropolitan areas has spurred the demand for specialty food products. This has kindled a demand
for Asian-style abalone products in the US market. The market niche is mainly for fresh
abalone meat used in Japanese sushi, but a brisk market for live cultured abalone has
developed in recent years (Oakes & Ponte 1996).

8.2.4

Southeast Asia

Lucrative markets exist for live abalone in Hong Kong, Taiwan, Singapore, Thailand and
other Asian metropolitan centres. The Hong Kong market is the largest and best established
of the Asian markets. As well as acting as the gateway to China, Hong Kong offers a direct
market for premium abalone products in many forms. Product demand throughout Southeast
Asia is based on established markets, which are similar to those in Hong Kong. As Asian
affluence increases, these market areas will become a more important market factor. The
combined influence of China and Southeast Asia will be significant in determining the
location and product concepts best suited for future production sites (Oakes & Ponte 1996).

8.2.5

Europe

Although Europe is not a major market area for cultured or fishery-caught abalone, there
is a regional demand arising from the traditional fishery for H. tuberculuta. This market is
concentrated in France, but there is some demand throughout the UK and the rest of Europe.
This demand is generally under-supplied and could be developed if supplies were available.
The European abalone species are small and traditional product presentations are well
suited to the smaller (100 g) abalone produced by culturists. Therefore, this region is of
great interest for future market expansion.

8.3

ABALONE PRODUCTION TECHNOLOGY

Though culture of abalone has developed in several countries, this section focuses on
developments in South America, Australia and New Zealand.

8.3.1

Chile

In Chile, aquaculture is an important income source for the economy. It produced nearly
853,000 tons with a value of US$5.3 billion by 2007, positioning Chile among the top ten


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world aquaculture producers (FAO 2009). Among the aquaculture resources exploited in
Chile, abalone was introduced in the late 1970s as a means of diversification, taking into
consideration its high commercial value and an unsatisfied demand worldwide (FloresAguilar et al. 2007).
Currently, the abalone industry is supported by two foreign species: Haliotis rufescens,
red abalone from California and Japanese or ezo abalone, Haliotis discus hannai from
Japan. Red abalone was first introduced in 1977, for experimentation in closed systems by
Fundación Chile and Universidad Católica del Norte (UCN) (Godoy et al. 1992). Later, in
1982, UCN introduced and adapted the culture technology of the Japanese abalone in collaboration with the Japan International Cooperation Agency (JICA). However, abalone
culture technology transfer began only in 1992, when red abalone culture was authorised,
in the sea off Chiloé Island in southern Chile, for a subsidiary company of Fundación Chile.
Japanese abalone commercial culture started in 1996 in northern Chile where several companies adapted the technology for land-based culture, as abalone seed were provided by
the UCN’s Center of Abalone Production. The first official red (1 ton) and Japanese abalone
(8 tons) production were registered by the Undersecretary of Fisheries of Chile, in 1998
and 2003 respectively. Exports began in 1999 with 36 tons of red abalone.
Currently, there are 19 farms in operation (11 in the north and eight in the south). Seed
production is mainly in the northern region, while most growout systems are land-based in
the north and in-water in the south of Chile. Since 2002, Chilean legislation has allowed
both species to be cultured in land-based semi-closed systems, while red abalone may also

be cultured in water-suspended systems between Seno del Reloncavi and Skyring Peninsula
in southern Chile (Resolution 30 September 2002). On the other hand, since 2004 the
culture of both species has been permitted in the sea but only in two of the three actual
culture regions located in northern Chile, and the stock has to be single-sex individuals and
sited over a soft substrate area (Subpesca 2006).
Currently, Chile is positioned as the fifth abalone producer worldwide with a production
volume of 479 tons and an estimated value of US$11.5 million. Red abalone production
accounts for 97.5% of total production, as this species has been well adapted to full-cycle
culture in northern and southern Chile (Enríquez & Villagrán 2008). On the other hand,
Japanese abalone has not adapted well because of its minor resistance to the Chilean culture
conditions (i.e. water temperature and type of macroalgae availability) and is actually considered as an emergent species (less than 5 tons a year). Unfortunately, no other abalone
species have been introduced, because Chilean legislation allows only these two species
to be imported and cultured, and efforts to introduce new exotic species (not endemic) had
been laborious, time consuming and unsuccessful. However, research on hybridisation
between red and Japanese abalone has proved to be potentially important to diversify and
to improve the Chilean abalone industry. Moreover, abalone farming can be considered a
young industry, with 70% of the farms just starting the phase of commercialisation and
exportation.
8.3.1.1 Conditioning and spawning induction
Abalone culture technology in Chile is fully integrated in the northern region, where hatchery, nursery and growout operations are undertaken by most of the farms. Only two of all
the southern farms possess all culture phases, and the rest are only in-water growout facilities that are provided with red abalone seeds in the range of sizes of 15–25 mm by northern


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235

farms. Hatchery facilities are composed of a broodstock area, a spawning area and a larval
rearing system.
Adult abalone are maintained in a specially designed unit, separated by sexes at

stocking biomasses of 25 g/L, in continuously running water at ambient temperature
and normal photoperiod 12D:12L. Water is usually filtered up to 25 μm, but some farms
use 50 μm. Acceptable water quality parameters are: water temperature 12–20 °C, pH
7.4–8.5, dissolved oxygen 7–10 mg/L, alkalinity 120–180 ppm, salinity 34–36 psu, ammonium 0.0–0.02 ppm, nitrite 0.0–0.2 ppm and nitrate 0.0–2.0 ppm. Feeding rates are around
10–20% of body weight per day, supplied with a fresh mixed macroalgae diet made up
mostly of Macrocystis sp. (90%), Lessonia sp., red algae Gracilaria sp. and green algae
Ulva sp.
Spawning adults normally used are 2 to 6 years old, with a visual gonad index of 2+ to
3+. If hybridisation is desired red abalones of 2–4 years old should be used to improve
fertilisation and hatching rates (unpublished data). Spawning induction is usually undergone by chemical stimulation using doses of TRIS-H2O2reactive (Morse et al. 1976) in
UV-irradiated water filtered at 1 μm after 1 hour of desiccation at ambient temperature. But
temperature and UV induction are also applied in some facilities, normally by raising
temperature gradually up to 5 °C at rate of 1 °C /hour. Normally, females are induced 15–30
minutes before males, but if hybridisation is undertaken males should be induced at least
15 minutes before females, to assure sperm availability as the fertilisation window for successful hybrid crosses is less than 20 minutes. At increasing egg age fertilisation rates drop
sharply (Lafarga-De la Cruz et al. 2010).
Female gametes are collected, and fertilisation is done in 20 L containers with sperm
concentrations in the order of 106 sperms/mL for homospecific crosses, and 107 sperms/mL
for heterospecific crosses (Lafarga-De la Cruz et al. 2010), and contact times around 2–6
minutes. Fertilised eggs are rinsed several times by decantation with UV-irradiated water.
Finally, fertilised eggs are placed forming a monolayer at the bottom of the hatching tanks
(50–100 L) and left static overnight, in a controlled-temperature room (17 °C).
After 16–18 hours, trocophore larvae hatch out and they are collected and selected
(>150 μm) in upwelling tanks for its larval culture period of 5 to 7 days, depending on
water temperature. Antibacterial treatments are recommended daily during this period, as
well as maintenance activities. Normal larval development is followed daily by microscopic
observations. Both closed systems and flow-through systems are used for larval culture,
and when the abalone larvae are competent (observation of the third tubule in cephalic
tentacles, and characteristic larvae’s foot movements) they are transferred to the post-larval
and juvenile tanks.

8.3.1.2

Nursery technology

The nursery facility for rearing abalone from post-larval to juvenile seed size (17–28 mm)
is based on the Japanese plastic plate system for larval settlement (Fig. 8.1). Preconditioning
of plates is normally with naturally occurring diatoms, but some farms also use cultured
microalgae (mainly Ulvella sp., Cocconeis spp. and Navicula spp.).
Abalones remain in nursery between 3 and 10 months, depending on the type of culture
system used. Land-based systems use abalones of 10–15 mm in shell length into the production system, where they are maintained for 24–48 months. On the other hand, in-water
(non-land based) systems use slightly bigger animals (20–25 mm) for grow-out.


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Recent Advances and New Species in Aquaculture

Fig. 8.1

Japanese plate system for post-larval and juvenile culture.

8.3.1.3 Growout technology
Abalone farms in the north are characterised by land-based growout operations employing
a substantial infrastructure; with many raceway tanks (Fig. 8.2) and integration of all phases
of production.
The growout tanks are 10 × 1.5 × 0.7 m, made of fibreglass, with a total volume around
11,000 L, with compartments having a conic-shaped bottom to facilitate the cleaning
process. They have 6 baskets inside (1.5 × 1.5 m and 0.6 m) (Fig. 8.3), made of plastic mesh
(6 mm hole diameter) and plates where the abalone is attached. This makes a total surface
of 100 square metres available for the abalone, and the plates hold the organisms off the

bottom where the waste debris from the abalone and algae is accumulated. A 1 mm thick
HDPE plastic plate covers each basket and weights are added on to keep the shelters inside
the water. Ambient temperature seawater is used in a flow-through system. The seawater
exchange rate is 9 tons per hour, and filtered seawater to 90 μm is used. Air is pumped to
each tank constantly.
The main food for growing out abalone is brown algae. Three brown algal species are
normally used: Lessonia trabeculata, Lessonia nigrescens and Macrocystis integrifolia,
with L. trabeculata being the most abundant. In the north, there is a regulation that only
registered companies may harvest kelp and they have to comply with scientific management
regulations in order to maintain the sustainability of the resource. Most of this kelp is


Abalone Culture

Fig. 8.2

237

Raceways growout culture system (P. Camanchaca Company, Caldera Chile).

harvested at low tide and is cut with a knife by fishermen holding contracts with these
companies.
The capacity of abalone per basket and shelter is constant and the number depends on
the abalone size. Two times a week the abalone are fed ad libitum, and the cleaning of the
tank depends on the time of the year and the algal feed but is normally once a week. The
tank is emptied and the tank surfaces are scrubbed with a brush and then refilled with fresh
seawater.
Most of the land-based abalone aquaculture farms in Chile monitor water quality as
temperature and oxygen once a day, and salinity and phytoplankton and bacteria at least
once a month. In compliance with the regulations of the federal agencies (Decreto Supremo

No. 90/1996. Ministry of Economy), levels of suspended solids, oxygen, ammonia and
temperature amongst other factors have to be continuously monitored. The exact monitoring requirements and their frequency varies, however, according to the size and location
of the farm and type of feed used.
In the south of the country, sea-based growout systems are widely used. The small
farmers use the barrel culture system (Fig. 8.4), and only the larger production companies
with inventories over 2 million abalone use cage-based growout systems. These are either
plastic moulded cages or iron-galvanized structures covered with netting. The cage size is
normally 2 × 1 × 1 m, but the most advanced cages are 3 × 1 × 1 m. These cages (Fig. 8.5)
have vertical plates as surface for the abalone to attach. In these plates a maximum capacity
of 65% of the total surface area of abalone is allowed.


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Fig. 8.3

Baskets with shelter plates for juvenile culture.

Fig. 8.4

Barrel abalone growout system.


Abalone Culture

Fig. 8.5

239

Abalone growout cage with its HPDE plastic plates.

These containers are suspended in a typical long line, and the kelp Macrocystis pyrífera
is the most widely used algal species to feed abalone. To operate the culture containers the
bigger farms use barges with a hoist to lift the cages. The Macrocystis feed is harvested
from small boats and cut with a knife. On the small farms staff collect the seaweed manually, while the bigger companies pay local fishermen to supply the algae. Macrocystis is
abundant in summer, but almost disappears in winter, forcing farmers to purchase cultured
red algae, Gracilaria chilensis. While there is constant supply of cultivated Gracilaria in
the south, the growers claim that Macrocystis produces much better abalone growth rates.
No kelp harvest permits are required in the southern regions.
Artificial feeds are used in some phases of the abalone growth, especially in land-based
farms in the north, in both nursery and growout operations. At some land-based farms,
abalone of all sizes receive a combination of artificial and kelp diet.
No manufactured diets are used on the in-water farms because environmental regulations
restrict aquaculture operations using formulated feeds. As a result of the large-scale salmon
culture in the region, aquaculture operations using pelleted feeds are deemed ‘intensive’
farms and sea concessions will only be granted if they are a minimum of 2.8 km from
neighbouring concessions. This makes it very difficult to find suitable areas for abalone
culture that comply with this regulation. As a result all farms in the south use seaweeds
as feed.
One company in the north has experimented with a recirculation system for more than
five years and it is proving very successful.


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Recent Advances and New Species in Aquaculture

8.3.2

Australia

In 2008, abalone aquaculture emerged as one of the fastest-growing agribusiness sectors
in Australia. With 850 tons produced in 2006/7, worth AU$42.5 million to the Australian
economy, this is estimated to grow to 1,500 tons over the next five to ten years, worth $75
million (Fleming 2008).
8.3.2.1 Conditioning and spawning technology
Until recently it had been assumed that Australian abalone farmers have found it far more
reliable to collect conditioned animals from the sea rather than condition them in tanks
(Fleming & Roberts 2001). However, high-quality gametes can now be obtained in winter
from H. laevigata held in a flow-through broodstock system developed by researchers from
the Western Australian Fisheries Department and industry (Freeman et al. 2006).
Water temperature is considered the main exogenous factor that regulates the reproductive cycle of abalone (Landau 1991; Hone et al. 1999; Fleming & Roberts 2001; Maguire
2001; Plant et al. 2003). Fleming and Roberts (2001) indicated that for H. rubra temperatures between 15 and 17 °C are optimal. In a study undertaken at Ocean Wave Seafoods
farm at Lara, Victoria, Plant et al. (2003) determined that H. rubra can be brought into
spawning condition when kept at constant temperature (18 °C). The best spawning results
were achieved after 120 days, when about 2 million eggs were spawned per female in 60%
of those tested, with a 75% fertilisation rate. The results clearly showed that conditioning
at a constant, increasing temperature delivers an increase in spawning success. The researchers believe the process should be applicable to other species.
Fleming and Roberts (2001) found that temperatures between 17 and 19 °C were optimal
for conditioning H. laevigata. In Western Australia, Freeman (2001) has found that H.
laevigata can be spawned all year round when water temperatures in the conditioning
room ranged from 14.2–19.23 °C. The most successful spawning events with highest egg
productions occurred out of the ‘natural spawning season’ in most groups. Spawning events
during this period can be highly beneficial to farmers as they can take advantage of the
enhanced growth of juveniles during the early summer months. Animals can be weaned
off the plates before the highest summer temperatures occur. High water temperature
during the weaning process can cause high mortalities in some regions of South Australia
(Maguire 2001).

Abalone can be stimulated with a single stimulus, or a combination of stimuli including
temperature changes, treating seawater with UV, ozone or hydrogen peroxide, handling
animals, or exposing them to air, depending on the species of interest (Maguire 2001). Hone
et al. (1999) outlined the procedure for spawning H. laevigata as follows: place the abalone
in clear aquaria and reduce the light and noise levels. After a few hours of acclimation in
ambient temperature water, activate the UV filter. If after 5 hours there is no activity, further
stimulate the abalone by placing an immersion heater in the tanks and rapidly raise the
temperature by 3–5 °C.
8.3.2.2

Hatching

Fertilised eggs from H. laevigata hatch after approximately 16 hours at 18 °C and are called
trochophore larvae. Newly hatched trochophore larvae swim to the surface and then can
be easily separated from the unhatched eggs and discarded egg cases by decanting off the


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241

top water layer into a clean tank for subsequent larval rearing (Maguire 2001). Abalone
Farms Australia (AFA) in Tasmania use a system where the larvae hatch from the negatively
buoyant eggs on the bottom of a tank and swim to the surface of the tank where there is a
small weir on the sides that leads directly to the larval rearing tanks. This system requires
minimal labour (Cropp, pers. comm. 2002). The non-feeding larvae develop over about
five days at 17 °C to 18 °C and about four days at 20 °C. Densities are kept at less than 25/
ml to ensure the highest water quality, and to reduce the chances of bacteria growing on
the tank surfaces (Maguire 2001). Survival rates of over 80% are common if proper care
is taken during larval rearing (Fleming & Roberts 2001).

8.3.2.3 Nursery phase
Towards the end of larval development, the larvae sink to the bottom of the container
and begin exploring for a suitable surface for settlement (Maguire 2001). Benthic biofilm
consisting of bacteria and mixed species of diatoms growing on PVC settlement plates
have traditionally been used as a settlement substrate in abalone nurseries worldwide.
This process is unpredictable and larval settlement rates can be low (1–10% of larvae)
(Daume 2003). Enhanced settlement up to 80% has been obtained in small-scale experiments through the use of the non-geniculate coralline red alga, Sporolithron durum (Daume
2003).
Currently naturally developing diatom films on plastic plates are predominantly used as
the settlement cue in abalone nurseries in Australia. Some diatom species produce better
settlement than others; for example Daume (2003) found that H. laevigata settled particularly well on the diatom Navicula ramosissima. Isolating particular diatom species and
growing them in monoculture before inoculating settlement tanks in the nursery provides
greater control. This practice has not, however, been embraced by the industry because it
is believed that the gain does not justify the extra costs involved in the scale-up diatom
culture site. Roberts and Lapworth (2001) explain that some diatom species are not good
for settlement, and strains that are excessively mobile or form 3-dimensional colonies can
prevent successful settlement. Therefore con-specific substrate films may play a significant
role in increasing settlement rates.
Hatcheries in Japan culture the microalgae Ulvella lens to improve settlement of the
Japanese abalone Haliotis discus hannai (Takahashi & Koganezawa 1988). Takahashi and
Koganezawa (1988) reported settlement rates of 67% on U. lens, which was not previously
grazed on by juvenile abalone. Pre-grazed U. lens yielded a settlement rate of 93–100%
(Takahashi & Koganezawa 1988; Seki 1997).
The first investigation of the settlement of Australian abalone species on U. lens was
conducted by Daume (2003), who found that settlement for H. rubra was higher on U. lens
than on diatom films. This study suggested that settlement plates seeded with U. lens could
induce high and consistent settlement of H. rubra. In addition, H. laevigata settled well on
U. lens compared to some diatom films. But more experiments are needed to explore the
abalone growth and settlement rates achieved on different diatom species and cell densities
(Daume 2003).

Settlement and metamorphosis occur typically within one to three days after the larvae
are introduced to the settlement tank (Maguire 2001). The transition from a free-swimming
larva to a juvenile, living permanently on a hard surface, is a critical phase in the life of
an abalone and mortality can be very high (∼90%) although the technology is improving
(Daume 2003).


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8.3.2.4 Growout phase
The weight of the meat compared to the length of the shell is referred to as the meat weight:
shell length ratio. This ratio is important for farmers, because though the product is normally sold as net meat weight, shell length is normally used to assess the size of abalone.
Therefore, the aim of growout phase for farmers is to produce abalone with greater meat
content. Freeman (2001) found that abalone reared at high densities have a higher meat to
shell length ratio than those cultured at lower densities.
In Australia, abalone is usually cultured on land using tanks, troughs or raceway
systems. Additionally, abalone can be reared in barrels or sea-cages hanging from
buoys or rafts (Maguire 2001). There is currently much greater emphasis on land-based
growout systems than sea-based systems in Australia. A wide range of system designs are
currently implemented in the country, ranging from deep to shallow and round to rectangular tanks.
An early land-based system in South Australia for H. laevigata culture used a ‘surfboard’
design, which was shallow concrete tanks/raceways, usually with a length of approximately
2 m. These small ‘surfboard’ raceway tank systems are usually sited indoors or in shade
cloth enclosures. The ideal slope for a raceway is 1:100, which helps to prevent mass
mortalities in the event of a pump failure by allowing the tanks to drain but also allowing
the bottom surface to remain wet. Shelters (hides) are not used since they disrupt the water
flow (Freeman 2001).
There is also a culture system based on much larger concrete tanks using the same

principles of shallow water depth and high water exchange. It employs a shaded outdoor
system similar to the ‘surfboard’ system. This is also currently being used in South
Australia.
Some growers have successfully adapted the typical ‘Taiwanese’ culture method of deep
tanks with strong aeration and numerous shelters for refuge (Forster 1996). These tanks
are designed so they can be drained regularly to remove solid wastes. They seem particularly well suited to H. rubra, but are also used for H. laevigata (Maguire 2001). A farm in
Tasmania currently operates this system successfully to cultivate H. laevigata.
Annual survival rates can be 80–95%, with growth rates of 20–30 mm a year in landbased systems for H. laevigata in the southern regions of Australia (Fleming 1995). These
rates are not always achieved, however, as growth rates vary significantly with the seasons
(Fleming & Roberts 2001).
Barrel or cage culture for abalone offers a low capital cost alternative, but can have high
maintenance costs (Forster 1996). The barrels or cages can be hung from longlines supported by buoys or attached to rafts and large cages that can be placed on the ocean floor,
provided that precautions are taken to prevent predation by crabs and starfish. Supplying
feed to submerged cages has been simplified by the development of a surface feeding
system that pumps feed from a surface vessel into the rafts or cages on the ocean floor
(O’Brien 1996a,b). The highest growth rates achieved in a trial involving a range of locations, culture systems (land- and sea-based) and species in Western Australia was with H.
laevigata grown in barrels at Albany (Fleming & Roberts 2001).
The water flow rate is critical because it must be sufficient to encourage feeding behaviour, maintain dissolved oxygen levels and remove wastes, but not so fast as to wash away
the feed before it can be consumed. Stocking density and feed type are important factors
when using this culture system. In general, higher stocking densities in land-based systems,


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243

with most of the floor area covered by abalone, encourage more uniform distribution of
H. laevigata. Throughout the growout phase, abalone densities are regularly reduced and
size grading is carried out (Edwards et al. 1999). Biofouling can greatly increase the maintenance costs of production systems and can directly smother the abalone by covering the
respiratory pores. New Australian technology aimed to reduce biofouling on molluscs, and

plastic mesh based growout systems, may be critical for the success of sea-based abalone
farming in Australia (Maguire 2001).

8.3.3

New Zealand

Paua (Māori name) is the common name for abalone in New Zealand. Three species of
abalone occur naturally in New Zealand; black foot paua (Haliotis iris) (Fig. 8.6) yellow
foot paua (Haliotis australis) and white foot paua (Haliotis virginea). Black foot paua
(Fig. 8.8) is the largest abalone species in New Zealand and is most commonly found in
shallow waters at depths less than 6 m all around mainland New Zealand, Stewart Island
and the Chatham Islands. They often form large clusters in the sub-littoral zone on open,
exposed coasts where drift seaweed accumulates and there is good water movement. Black
foot paua grow to about 180 mm in shell length (the legal size for wild harvesting is
125 mm, measured as the longest shell length).

Fig. 8.6

Paua abalone.


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Recent Advances and New Species in Aquaculture

Fig. 8.7

Trays with black foot paua abalone.

The New Zealand paua farming industry had its beginning in the mid-1980s when
hatchery techniques were developed for the New Zealand species. Paua farms in New
Zealand have traditionally been land-based and configured to operate on flow-through water
supply where the water is pumped from the sea, over the paua and then allowed to return
to the sea.
Recirculation technology has gained favour in recent years and offers several advantages
over flow-through by improving performance, raising efficiencies, reducing costs and
reducing risk. These advantages include maintaining consistent rearing temperatures,
protecting farms from fluctuating environmental conditions and improving overall biosecurity. Although the trend is towards recirculation, at least two farms currently operating
use sea-based barrel culture technology; however, the focus for these is on the production
of paua pearls, which employs a more extensive approach using freshly harvested
seaweeds.
Early efforts on paua commercial production used seaweeds for feed. However, now
most land-based farms rely on manufactured pellet feeds because of their convenience,
consistency of food quality, difficulties in obtaining sufficient quantities of seaweed and
the additional benefit of reducing the black pigment in the foot.
Only black foot paua are currently farmed in New Zealand. This is mainly because of
the larger size of the black foot compared with the other two New Zealand species, and
their iridescent shell coloration, utilised for the production of cultured paua pearls. Paua


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aquaculture has excellent potential for New Zealand due to strong overseas demand and
high prices attained for live meat (more than NZ$60 per kg).
Currently, the industry in New Zealand is based around 11 farms, mostly onshore
systems that on-grow hatchery-reared juveniles to market size for their meat. The largest
of these is OceaNZ Blue Ltd (OBL) in Northland, which produces the bulk of New

Zealand’s farmed abalone. OBL is on track to become the first 100 ton production facility
in New Zealand and operates using a semi-recirculating system. Two paua farms are focusing primarily on the production of juvenile paua for the purpose of reseeding to enhance
coastal areas depleted of wild stocks. This area of production is expected to gain momentum
as enhancement efforts increase and the potential to identify reseeds from wild stock are
realised through the development of molecular markers.

8.4
8.4.1

TECHNOLOGICAL DEVELOPMENTS
Polyploid induction

Chromosome set manipulation in molluscs has received wide attention in the past two
decades. Research has primarily focused on the induction and evaluation of triploidy in
bivalve species of commercial importance (Beaumont & Fairbrother 1991; Nell 2002). The
principal value of triploids for aquaculture arises from their sterility, presumably because
of failure in synapse of the three sets of chromosomes during meiosis. Sterility may lead
to faster growth of (adult) triploids owing to energy reallocation from reproduction to
somatic growth. Sterility may also result in better meat quality of triploids in association
with their reduced spawning activities (Beaumont & Fairbrother 1991).
Triploid animals are produced, by inhibiting the release of the first or second polar body,
through the application of a chemical or environmental stress soon after fertilisation. The
retention of an extra set of chromosomes within the developing embryo results in an animal
containing three sets of chromosomes per cell (triploid) instead of the usual two sets
(diploid). Triploidy can be induced using multiple techniques.
8.4.1.1 6- dimethylaminopurine exposure
Fertilised eggs can be exposed to 100 μM solution of 6-DMAP (6-dimethylaminopurine)
between 15 and 20 minutes post-fertilisation. Following a 15-minute exposure to 6-DMAP,
the eggs are rinsed and placed in hatching trays.
8.4.1.2 Cytochalasin B (CB) exposure

Induction of triploidy has been achieved applying CB at a concentration of 0.70 mg/L after
27 minutes for a duration of 10 minutes. Eggs are then rinsed and placed in hatching trays.
8.4.1.3 Temperature shock
Exposure of fertilised eggs to 3 °C at 15 minutes post-fertilisation for duration of 10 minutes
and/or exposure to 26 °C water 15 minutes post-fertilisation has induced triploidy in various
abalone species.


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8.4.2

Hybridisation

Intraspecific (crossbreeding) and interspecific hybridisation within the family Haliotidae
can be used as a strategy to improve the profitability of abalone farming. An effort by
farmers to reduce production costs rather than increase the price of their product may
become a more realistic method of increasing profitability. It would be expected that hybrids
that display positive characteristics of heterosis would be an integral part of such an effort.
However, as pointed out by some authors, if hybrids are to be used for aquaculture, it is
fundamental that they are made sterile or that efficient methods to prevent escape are
developed, because of the abalone’s established ability to produce offspring among them
(F2 progeny) and backcrossing with parental species (gene introgression risk). Escape could
lead to a possible genetic impact of hybridisation on natural abalone populations.
Hybrids often have superior characteristics than their parents, such as greater in size,
resistance to disease, number of offspring produced. Heterosis, or hybrid vigour, is a term
used to describe the phenomenon in which the performance of an F1 hybrid, generated by
the crossing of two genetically different individuals, is superior to that of the better parent

(heterobeltiosis) or average between both parents (middle parent heterosis). Heterosis has
been extensively used in breeding programmes of aquaculture resources as a way for
genetic improvement of cultured species (Hulata 2001). There are two major hypotheses
that have been promulgated to explain heterosis: the dominance hypothesis and the overdominance hypothesis. The dominance hypothesis suggests that heterosis is due to cancelling of deleterious recessives contributed by one parent, by dominant harmless alleles
contributed by the other parent in the heterozygous F1 (Jones 1917). On the other hand,
over-dominance hypothesis assumes that the heterozygous combination of the alleles at a
single locus is superior to either of the homozygous combinations of the alleles at that locus
(Shull 1908). As already pointed out in some research, intra-specific cross breeding has
produced positive heterotic hybrid abalones.
With regard to the analysis of the genetic change in parent abalone and their hybrids,
Wan et al. (2001) obtained inter- and intra-population similarity indexes and genetic distances by Random Amplified Polymorphic DNA (RAPD) analysis of H. discus hannai and
H. discus discus, and their reciprocal hybrids. From the 113 bands of RAPD analysis some
were special (diagnostic) for each kind of abalone and some others were common between
two and three of the kinds. Results of inter-population similarity indexes showed greater
variation in hybrids, whereas genetic distances between the hybrids and the two parental
species differed, being more similar to H. discus discus for both hybrid crosses. Later on,
Wan et al. (2004) continued their comparative studies on genetic diversities among these
two parental species and their hybrids, in order to understand better the process of heterosis,
using AFLP as molecular markers. Results showed significant differences between parental
populations in 88 out of 552 loci found. In hybrids, more loci with lower frequency were
amplified, whereas those with 0 and 100% frequency were less amplified when compared
with parents. Lower similarity indexes and higher heterozygocity in hybrids resulted in an
increased genetic diversity of hybrids. And as noted before with RAPD analysis (Wan
et al. 2001), the genetic distances between reciprocal F1 generations and H. discus discus
were both smaller than those between hybrids and H. discus hannai. Recently, Liu and
Zhang (2007) conducted a genetic study using AFLP markers to analyse the F1 intraspecific hybrid family of H. discus hannai from two distinct geographical populations.
Results showed fragments exclusively for females, males and certain others common for
both, some segregating in agreement with Mendelian 1:1 ratio and other with 3:1 ratio,

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247

showing ratios of segregation distortion of 27.4, 25.9 and 33.9%, respectively. The authors
hypothesised that segregation distortion may be associated with the incompatibility of
genes between the two populations of H. discus hannai used in this study (Liu & Zhang
2007).
Aquaculture has produced hybrids to improve growth and survival in the past. The yabby
industry found that the crossing of female Cherax rotundus and male Cherax albidus produces only male progeny that grow faster than mixed sex groups of C. albidus. The results
of trials under model pond conditions found the hybrid to have a final harvest value 4.6
times greater than that of C. albidus yabbies (Lawrence 2004). This hybrid offers considerable potential to increase the profitability of yabby farming. Hybrid striped bass are currently cultured in the United States and other countries, including Taiwan, Israel and Italy.
Hybrid striped bass are a cross between striped bass, Morone saxatilis and white bass, M.
chrysops. When the female parent is a striped bass the hybrid is called a palmetto bass;
when the female is a white bass the hybrid is called a sunshine bass. Ludwig (2004) found
that at 5 days of age the palmetto bass are 6 to 9 mm long, while those of sunshine bass
are only 3 to 5 mm in length. Landau (1991) in an experiment using a hybrid from male
blue catfish and female channel catfish, grown for 220 days in earthen ponds, found that
the harvest of the hybrids was 13.5% greater than that of channel catfish. Additionally, the
hybrids were more easily captured by seining, were more uniform in size and had a greater
dress-out percentage (weight after the head and skin were removed and it is eviscerated,
divided by the live weight of the fish).
Heterotic effects in the hybridisation of abalone have been reported as increased growth
and survival (Leighton & Lewis 1982; Koike et al. 1988) compared to those of the parent
species. Hoshikawa et al. (1998) studied the heterotic effect of hybridisation on growth.
It was only observed at high water temperature (18 °C) in the form of superior growth
rates and not at the lower water temperature (8 °C) in the cross between pinto abalone,
Haliotis kamtschatkana and ezo abalone, H. discus. The daily shell growth was significantly
higher in the hybrid at 18 °C with 33.4 to 55.6 μm/day compared to 6.5 to 10.9 μm/day for
pinto abalone and 31.2 μm/day for ezo abalone (Hoshikawa et al. 1998). Heterotic effect

in growth and survival can also be observed at ambient temperature as demonstrated by
Wang and Jiachun (1999), who found the growth and survival rates in the F1 offspring
from the cross breeding of red abalone H. rufescens and pacific abalone H. discus hannai
were higher than those of H. discus hannai. Juveniles of the hybrid between Haliotis
rufescens and Haliotis fulgens, and also between H. rufescens and Haliotis sorenseni
displayed superior growth at ambient temperature than the parent species (Hoshikawa
et al. 1998).
Hybrid abalone have been produced in Australia by crossing female Halitosis rubra and
male H. laevigata abalone (Freeman 2001). These individuals have been produced in an
attempt to find an abalone that has the best characteristics in terms of growth rate, meat to
shell ratio, meat texture and market appeal. The ‘tiger ’ abalone which is a cross between
a female H. laevigata and a male H. rubra, is commercially cultured in Tasmania by Tas
Tiger Pty Ltd. Hone et al. (1999) indicated the tiger abalone has significant market value.
A hybrid between H. laevigata and H. scalaris has recently been produced at SAM abalone
in Port Lincoln, South Australia. It has shown a faster growth rate during the months between
December to March than that of both parent species. Fig. 8.8 is a photograph of H. scalaris,
the hybrid, and H. laevigata and clearly demonstrates the size difference. This particular
hybrid cross has also been found to occur in the wild. The Western Australian Fisheries
Department has specimens that have been found in the south west of Australia (Fig. 8.9).


Fig. 8.8

Left to right: H. scalaris, H. laevigata × H. scalaris (hybrid) and H. laevigata.

Fig. 8.9 Wild H. laevigata, H. laevigata × H. scalaris (yybrid) and H. scalaris found in Western
Australia. (Please see plate section for colour version of this figure.)


Abalone Culture

8.5

249

FUTURE POSSIBILITIES

In South America, the biggest constraint for the industry is considered to be the supply of
abalone feed. Some farmers are searching for a better supply of algae, including culturing
Macrocystis pyrifera as the solution while some others are experimenting with manufactured diets of their own production or from domestic and foreign feed-producing mills.
In New Zealand, prohibitive harvesting costs and limits on harvesting have resulted in
abalone farmers using artificial feed pellets. Since abalone needs to actively search for static
artificial food, studies are being undertaken to improve the attractiveness of such feeds by
the addition of chemical attractants, feeding stimulants or dried seaweed fragments (Allen
et al. 2006).
On the other hand, artificial diets have been considered expensive and unsuitable for
ocean-based longline culture of abalone and suitability of a variety of seaweeds is being
investigated (Qi et al. 2010).
Abalone production systems need to optimise culture configurations to improve productivity. In Chile, efficiencies of basket and lantern nets suspended in seawater tanks were
compared for growth and survival of juvenile abalone (Pereira & Rasse 2007). Lantern
systems were found to have a larger carrying capacity while occupying less water column
space. The lantern nets provided better growth, and were more economical and easier to
handle (Pereira & Rasse 2007).
Recirculating aquaculture systems (RAS) are considered to have reduced environmental
impacts. Installation of baffles within the RAS culture tanks has been trialled to allow
high-density culture (Park et al. 2008).
Recently, Integrated multi-trophic aquaculture (IMTA) involving integration of fed
species and extractive species been developed and is gaining recognition as a sustainable
approach to aquaculture (Nobre et al. 2010). In South Africa, IMTA has been implemented
using seaweed Ulva lactuca and abalone Haliotis midae, where the algae take up the dissolved inorganic nutrients from the system and the produced algal biomass provides renewable feed for the other cultivated species, abalone (Nobre et al. 2010).

Another major challenge for the industry is to diversify the market. Most abalone were
sold in Japan in the past but now Chinese, United States and European companies are
making big efforts to develop the market and specifically the presentation of canned abalone.

8.6

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