1. Abalone are a type of sea snail that live in coastal waters and have a single spiral shell with respiratory pores. They are farmed in many countries for their meat and shell. 2. Abalone reproduction involves external fertilization, with males releasing sperm that triggers females to release eggs. Larval development proceeds through trochophore and veliger stages over 1-2 weeks before settling. 3. Abalone farming began in the 1950s in Japan and China to meet demand and prevent overfishing. China is now the world's largest producer and consumer of farmed abalone.

1. Taxonomy, Biology and Farming of
abalone
By:
B. Bhaskar

2. Introduction
• Abalone are a type of sea snail, a gastropod mollusc, that grows in coastal seawater.
• Members of the Haliotidae family, they range in size from 4 to 10 inches (10 to 25 cm).
• These marine creatures have a single shell on top with a large foot underneath, which is used
for moving and eating.
• The shell is flat and spiral-shaped, with several small holes around its perimeter, and it is
lined with mother of pearl, which is sought after for button, trinket and jewellery making.
• There are more than 100 species of abalone worldwide, around 15 species of which are
grown in aquaculture.
• Ten species are considered of commercial value, and mainly occur in Korea, Japan,
Mexico, South Africa, Southern Australia, New Zealand, United States of America, and
China.
• H. discus hannai are found in the northern waters while the southern waters are the
habitat for species such as Haliotis gigantea, Haliotis sieboldii, Haliotis discus, etc.
• The world's commercial species include Haliotis ruber in Australia, Haliotis iris in New
Zealand and Haliotis midae in South Africa.
• Ten species are distributed in the Pacific Coast of North America, 3 of which are
commercially important.
• Haliotis rufescens (also known as the Red Abalone) reaches a maximum length of 30 cm.
• Normally, abalones are found at depths up to 30 metres in the intertidal zone.
• Abalones have their maximum population density at depths ranging between 3–10
metres where seaweeds, their natural food, grow abundantly.

3. • Abalone farming began in the late 1950s and early
1960s in Japan and China, when it became necessary
due to high demand and overfishing.
• In recent years, growth of the abalone industry has
been made possible by a number of innovations in low-
cost seed production and highly efficient sea-based
cage culture systems.
• By 2018, global aquaculture production of abalone had
reached 46,400 tonnes per year.
• China is the world’s largest producer and consumer of
abalone, and other important producers include
Taiwan, Japan and Korea, followed by Australia,
Canada, Chile, France, Iceland, Ireland,
Mexico, Namibia, New Zealand, South Africa,
Spain, Thailand, and the United States.

4. Taxonomic Hierarchy
•
Kingdom: Animalia – Animal, animaux,
animals
• Subkingdom:Bilateria
• Infrakingdom:Protostomia
• Superphylum:Lophozoa
• Phylum: Mollusca – mollusques, molusco,
molluscs, mollusks
• Class: Gastropoda Cuvier, 1797 –
gastropods, slugs, snails, escargots,
gastéropodes, limaces, caracol, caramujo,
lesma
• Subclass: Prosobranchia Milne-Edwards,
1848
• Order: Archaeogastropoda Thiele,
1925
• Superfamily: Pleurotomarioidea Swainson,
1840
• Family: Haliotidae Rafinesque, 1815 –
abalone
• Genus: Haliotis Linnaeus, 1758 –
abalone
• Species: Haliotis rufescens Swainson,
1822 – red abalone, abulón rojo

5. General appearance
• From the veliger stage the bilateral symmetry of the abalone body turns into
a spiral shape. Its body is divided into three parts: head, foot and saccate
intestine.
i) Head
• The head is located on the anterior part of the body and is bilaterally
symmetrical. It comprises a mouth, appendages and sensory organs.
Compared to other shellfish, abalones have a developed and complex head.
It has a pair of tentacles and two eyes at the tip of eye stalks which originate
at the bottom of the tentacles.
ii) Foot
• The foot of the abalone is a creeping organ of muscular tissue which lies on
the ventral part of the body. The well developed foot has a broad “sole”
which allows the animal to strongly adhere to rocks or other hard substrates.
The epipodes that occupy the lower part of foot form a broad-plate shape
structure, while the interior surface has ten pairs of brown stripes on a grey
background. Branch-shaped tentacles are typically found at the end of the
epipodes.
iii) Intestinal sac
• The intestinal sac is located on the dorsal side of abalone and has several
internal organs. On the outside, the mantle runs from the back to the ventral
margin. The abalone shell is formed by the secretion released from the
epidermal cells placed at the front margin and tip of the mantle.

6. iv)Shell
• Abalones belong to one of the most primitive gastropods and its round,
elliptical or ear-shaped shell has a row of respiratory pore located along the
left margin. As the animal grows, older pores are successively filled in and
closed. The number of open pores varies among different abalone species.
Shell exterior and interior color varies with species, but it is an unreliable
form of identification since the color may not be clearly visible or the
original description may not be accurate.
• The shell comprises three layers. The cuticle, which is the outer layer, is an
organic matter purely formed of concholin. It is very thin. The hard shell or
middle layer (horny layer) is composed mainly of calcium carbonate crystals
embedded in concholin whose chemical components are similar to the one in
cuticle layer. The innermost layer called pearl layer has chemical
components similar to the horny layer.
• The pearl layer is made of secretions occurring over the surface of the entire
mantle. The cuticle and horny layers are secreted by the mantle margin and
the growth line appears on the edge of the shell. During the winter and
spawning season, or under adverse environment conditions, no growth
occurs, thus showing the growth stages and the physical condition of the
abalone.

7. Internal anatomy
i) Calyx lobe and radula
• In the pharynx cavity there is a pair of calyx lobes and a radula which are located at the anterior part of digestive
gland. These structures are important in terms of abalone taxonomy. The calyx lobe is made up of concholin and
serves as the feeding organ. The long radula moves back and forth, chopping down the food with its small teeth
(visible under a microscope) which is then further broken and absorbed during its passage through the
esophagus, crop, stomach, spiral caecum, and intestine.
ii) Digestive system
• The digestive system of abalone is placed on the left side of the adductor muscle located in the middle of the
body. The digestive organ consists of mouth, gullet, stomach, intestine rectum and anus (Fig. 2).
• Due to the spiral shape of the body, its digestive organs are curved, and the mouth and anus lay near to one side.
The mouth is gibbous and ovate in shape and its walls composed of thick muscular tissue.
• In the mouth are located the calyx lobe, radula and salivary glands. The gullet of the abalone is elongate and
narrow. The abalone stomach is saccate and V-shaped and placed next to the gullet. The vermiform appendix and
liver are attached to the stomach.
• The liver is placed at the right side of the adductor muscle, protruding in the shape of an ox horn. The intestine
and rectum start from the back side to the front margin of its body going round the left side of adductor muscle
and then it curves back to the front side again. The intestine length is 3.27 times that of the shell. The digestive
system of the abalone is long and complex, as it is with many herbivores.
• fig1. External features of an abalone without its shell (1-anus; 2-tentacle; 3-liver; 4-gill; 5-epipodium; 6-eye; 7–
10-mantle; 11–12-mantle tactus; 13-heart; 14-foot; 15–16-adductor muscle; 17-spiral intestine).
• Fig2. Digestive organs of an abalone (1-anus; 2-intestine; 3-liver; 4-gullet; 5–7-salivary gland; 8-radula; 9-
mouth; 10-stomach).

8. Respiratory, Circulatory and Nervous systems
The respiratory and circulation systems
• The gills, lying immediately below the shell pores, function as the respiratory organ of the abalone.
• There is a pair of gills at the centre of the respiratory chamber, the left one being bigger than the right one.
• The left and back sides of the respiratory chamber are closed so as to allow the water into the gills from the
upper and right sides of its head.
• The sea water undergoes gas exchange in the gills and runs out through the respiratory pores on the shell
along with other excretions from the anus and ostium.
• The circulatory system of abalone is characterized by its patency.
• The heart in the pericardial cavity consists of one ventricle and two atria.
• The blood is colourless and contains amoebocytes.
• The blood from the heart runs to the blood sinus placed between organs through the circulation system.
• The blood in the sinus runs to gill artery and then to the gill itself.
• Oxygenated blood then runs to auricle through the gill vein.
• Abalones have a pair of gill arteries and a pair of gill veins.
Nerve system
• The abalone nerve system is poorly developed. There are four pairs of brain ganglion located around the
mouth: foot nerve chain, intestine ganglion, side nerve chain and the nerve conjunction which are connected
lengthwise and crosswise
• Feg3. Nervous system of an abalone (1-brain-linked nerve; 2-brain ganglion; 3-nerve beside the brain; 4-nerve
under the brain; 5-side pedal ganglion; 6-pedal nerve; 7-ventral ganglion; 8-pedal nerve chain under gullet; 9-
intestine ganglion over the gullet; 10-gill ganglion).

9. REPRODUCTION AND GROWTH OF ABALONE
i) Reproductive season
• The breeding season and its duration vary according to species and also closely related to environmental
conditions of the habitat, generally being positively correlated with water temperature. The abalone spawning
season in Korea (DPR) begins in July/August when the seawater temperature is around 20 °C and in some cases
it lasts throughout September and/or October.
ii) Reproductive habit
• Abalone is a dieocious animal, with individuals of separate sexes. The gonad tissue can be visible when the shell
reaches about 30 mm in length, usually after one year. The gonad encircles the ox horn-shaped liver on the
right side or the back of the body. As the spawning season approaches the gonads are engorged with mature
gametes and their colour becomes distinct. Male and female specimens are easily distinguished. The female
gonad is either dark green or brownish, while the male organ is either milky-white or yellow. The gonads are
clearly seen under the edge of the mantle membrane or under the foot, and can be observed without
dissecting the specimen.
• Abalones usually spawn in the twilight of early evening or at dawn. Males usually release sperm first, therefore
stimulating females to spawn. Release of eggs or sperm by one animal usually triggers the spawning of many
gravid animals nearby. The eggs are fertilized in the open water. The gametes are released into the seawater via
the second respiratory pore. Male ejaculation appears like a streak of grey smoke and the female egg-laying as
blue smoke.
• One female measuring 7–8 cm in shell length may release 1 million eggs while a bigger one up to 10 million.
Generally the number of eggs laid amounts to 80 % of the fecundity. Female egg-laying is completed within 2–4
hours but male ejaculation lasts for a much longer time, usually as long as two days.
• In spawned individuals the gonads become thin and wrinkled, and lose their distinct colouration.

10. iii) Reproductive cells
• (a) Egg. The eggs of abalone are spherical. A matured egg cell measures 220 micrometer in
diameter, while the egg yolk is 180 micrometer in diameter.
• The transparent cellular membrane surrounding the egg is 40–50 micrometer thick.
• The eggs in the ovary are compressed and shaped like irregular polygons. Spawned eggs
immediately absorb seawater, become spherical in shape and sink to the bottom.
• In some cases, artificially stimulated spawning produces cylindrical or pearshaped eggs.
Most of these eggs are immature.
• The eggs can be classified into three categories: a) normal, b) eggs without egg membrane
and, c) eggs without colloidal membrane.
• The last two categories are immature.
• These immature eggs tend to form clumps; they are rarely fertilized, and even if successfully
fertilized, the embryo has an abnormal development.
• (b) Sperm. The gonad of a mature male has a yellow appearance, while that of immature
specimens are milky-white.
• The sperm has a lanceolate head and a long tail. The length of sperm head is 8 micrometer
and the tail 50 micrometer.
• Spermatocytes move actively after they have been released into the seawater.
• Their life time and fertilization potential is closely related to the water temperature and the
maturity of abalone itself.
• Sperm fertility lasts for 3 hours at seawater temperatures of 22–23 °C.
• Semen ejaculated by a male with an immature gonad is an irregular mass of cells which does
not disperse easily.
• Immature spermatocytes have an indistinct head and remarkably short tail, they move with
difficulty and die within an hour.

11. Development stages
iv) Development stages
• The first and second polar bodies are formed within 15 minutes after fertilization
at a seawater temperature of 20–21 °C. The pole bodies are located at the apex of
animal pole (Fig. 4-1). They are lustrous when observed under a microscope. Thirty
minutes after fertilization, the fertilized eggs undergo the first cleavage, the
embryo is now at the two-cell stage (Fig. 4-2), each cell measuring 120 micrometer
in diameter. The second cleavage takes place 80 minutes after fertilization (Fig. 4-
3).
• Two hours later, the third cleavage takes place, and the embryo is at eight-cell
stage. Of the eight cells, four are smaller than the others, the former to be carried
the side of animal pole and the latter the side of plant pole (Fig. 4-4).
• In 160 minutes the embryo becomes 16-celled (Fig. 4–5) and in 195 minutes, it
attains the morula stage (Fig. 4–6).
• Approximately 6 hours later, the embryo becomes slightly elongated having
reached the gastrula stage with the characteristic blastopore (Fig. 4–7).
• Seven and-a-half hours later, the ciliary belt appears on the developing embryo.
The embryo is now about 180 um long and 160 um wide. It begins to actively
rotate within the egg membrane with the aid of the ciliary belt and the apical hairs
(Fig. 4–8).
• The larva begins moving more frequently inside the egg membrane, and 10–12
hours later the membrane becomes thinner, until it finally bursts (Fig. 4–9).
• The newly hatched trocophore is 210 um long and 168 um in diameter. The free-
swimming trochophore is phototactic and therefore tends to move towards the
upper water layers. Approximately 15 hours later, the larva develops into the
veliger larval stage; the swimming cilia are now borne by a distinctive collar of
cells, known as the velum, surrounding the developing head (Fig. 4–10).

12. • At this stage the larva is 224 um long and 196 um wide. Within 26–28 hours, the later
veliger develops an eye spot, foot, operculum, and a protoconch similar to that of a snail.
• The larva always keeps its shell downwards and actively swims up and down the water
column with the help of the velum.
• When disturbed, the larva immediately retracts its foot and body inside the shell and seals
the aperture with a closable operculum.
• Three days later, while approaching the settling stage, the foot grows bigger and the velum
degenerates and disappears.
• Six days later, the larva reaches 300 um in length and 220 um in width.
• At this stage wrinkles appear on the peristomal shell and spread like a tuba (Fig. 4–12), and
as the shell grows outward, the aperture widens.
• Tentacles and eye spot appear on the head, epipodium tentacles develop as well as the
gills and the mantle membrane.
• When the abalone shell reaches 0.7 mm in length and 0.6 mm in width, epipodes appear
(Fig. 4–13) and 35–40 days later, it becomes a juvenile having the first respiratory pore (Fig.
4– 14, 15).
• This juvenile is 2.3–2.4 mm long and 1.8–2.1 mm wide, and the number of epipodium
tentacles are about 10.
• Fig. Developmental stages of an abalone (1-polar bodies appear on the fertilized egg - 15–
30 min.; 2-2-cell stage; 3–4-cell stage - 80 min.; 4–8-cell stage - 120 min.; 5–16-cell stage -
160 min.; 6-morula stage - 195 min.; 7-gastrula stage - 6 hrs.; 8-trocophore in the egg
membrane - 7–8 hrs.; 9-newly hatched trocophore - 10– 12 hrs.; 10-early veliger - 15 hrs.;
11-late veliger - 48 hrs.)

13. • Growth of abalone
• Genetic factors greatly determine growth. However there are several interrelated environmental factors
affecting the growth rate. The growth is greatly influenced by the level and type of nutrients available as well as
the range of environmental conditions which affect the physiological functions of the organism. Some of these
factors include feed, water temperature and stocking density. Abalone grows well at a water temperature of
about 20 °C. Abalones grow at about 2–3 cm a year; it takes 4 years to grow to the marketable size of more
than 9 cm. In a few cases, however, it grows only about 1 cm a year, so that it takes more than 8 years to reach
the commercial size. Under good feeding conditions, abalones grow 3–5 cm a year, particularly when the
juveniles are artificially released and raised in the open seawater. The abalone growth largely depends on the
season: at a water temperature below 6 ° C and during the spawning season, abalones tend to grow very
slowly. During this slow-growing period the abalone shell becomes characterized by a thick and dense annual
ring, by which the animal's age can be determined. Food preferences of abalone are in the following order:
phaeophyta, chlorophyta, and rhodophyta algae species.
• Developmental stages of an abalone - cont'd (12-peristomal stage - 6–8 days; 13-early larva with epipodes - 19
days; 14–15- juvenile abalone - 45 days).
• In artificial rearing, juvenile abalones may attain over 5 mm in 80 days. Four months after fertilization, they
reach more than 12 mm and can be fed with Laminaria, Undaria or other seaweeds.
• Figure 5 shows the relationship between the weight of abalone and the shell length.
• The DPRKorean experiences in abalone rearing show that H. discus hannai grows up to 3 cm in the first year,
5.5 cm in the second year, 7.5 cm in third year, and more than 9.5 cm in the fourth year. The weight increases
faster than the growth of shell. For example, if the length of the shell doubles, the weight increases eight-fold.

14. Food and feeding habits
• The feeding habits of abalones depend on the growth stage, body size and season.
i) Free-swimming and settling stages
• Up to the trochophore stage the growth is on the nutrients from the egg yolk. Veliger and settling larvae begin to feed on
unicellular algae and/or organic substances. More unicellular algae cells are taken in as the mouth widens and the parts develop
further.
ii) Juvenile and adult stages
• Juvenile abalone usually feed on benthic diatoms and small benthic organisms. Juvenile intake of food increases remarkably with
the appearance of the first respiratory pore; the feeding also becomes more active. Young abalones of 5 mm in length begin eating
young seaweeds and grow faster. At 13 mm long they feed on a great variety of seaweeds such as Laminaria and Undaria. Young
barnacles, bivalves and foraminiferans are also found in the stomach of abalones.
• The feeding habits of abalones ares also affected by the seawater temperature. Abalones seldom feed at a temperature of 8 °C,
while it takes in food up to 6 % of its body weight at 12 °C, and 15 % at 20 °C. Abalones are particularly active during the early
hours before sunset and sunrise. They maintain their weight when the feeding quantity is 0.61 % of their body weight.
• Abalone is an opportunistic feeder. In experiments where several feeds were given, the eaten rate was Laminaria 53 %, Undaria
pinnatifida 38 %, Ulva 6 %, and Porphyra 2 %.
The migration of abalone
• A newly hatched trocophore swims considerable distances in the water current for 3–7 days until it enters the settling stage.
From then on it becomes a benthic organism and moves with the aid of its foot. An abalone was observed to have moved 66 cm
in 1 minute over a glass surface. The moving habit of an abalone differs depending on the body size, time of day, and season. As
it grows bigger, it moves to deeper locations. Abalones tuck themselves under rock and stone in the daytime, and crawl around
in search of food at night, returning to their shelter before sunrise. Records show that abalones can move 50–80 m during 1
night. They migrate to shallower places or gather in small groups during the spawning season.
Redators and Parasites
• Abalone predators include various species of marine finfish, crustaceans, echinoderms, molluscs and others
i) Finfishes: Red skate, shark, flat bream, black porgy, perch, Sparus macrocephalus, Goniistiys quadricornis,
labridae, Stephanolepis cirrhifer, Microstomus achne, Canthigaster rivulatus, and congers.
ii) Crustaceans: Pigettoa gisdridens,Charybdis japonica,Panulirus versicolor
iii) Echinoderms: Seastar, Asterina pectinifers, Buidia maculaia
iv) Molluscs: Octopus, Thais clavigera

15. PREPARATION OF SPAWNERS
• Selection of spawners
• The number of spawners to be conditioned and used varies according to the
number of the young abalone to be produced and to the rearing method
and technical devices available.
• Up to the shell length of 5 mm, the abalone survival rate, which may range
from 1– 40 %, is affected by the rearing method and technical conditions of
the devices.
• Therefore, bearing in mind these conditions and the number of eggs to be
spawned a sufficient number of spawners should be used.
• The ratio of female and male is 4:1, and a good spawner should be at least
three years old and 7–9 cm in shell length.
• The bigger the spawner, the more eggs it bears.
• About 80 % of mature eggs are usually released into the seawater. It is
advisable to catch spawners in March/May and in October/November when
the water temperature is comparatively low.
• Much care should be given during the collection of spawners and
transportation to the breeding station.

16. MATURATION OF SPAWNERS
i) Conditioning of spawners
• Male and female abalones are bred separately. A proper system and devices should be installed to adequately collect spawned eggs
at anytime of the year.
• A 1-ton capacity plastic or concrete tank is used for abalone maturation. The optimum number of spawners per tank is 40–60
individuals. Corrugated plastic boards and V-shaped cement collectors are placed on the bottom of the tanks for the abalones to
hide and feed. A temperature control device should be installed to maintain a constant temperature of 17–20 °C during the
conditioning period. At this time, the amount of seawater exchanged should be adequate, according to the abalone biomass and
amount of oxygen consumed. The volume of water exchanged is calculated as follows:
where:
V=the amount of water exchange (litre/day)E=the amount of oxygen consumption (ml/kg/h)N=the weight of abalone (kg)T=24
hoursC1=the amount of oxygen in fresh water (ml/l)C=the amount of oxygen in rearing tank (ml/l)The amount of water exchange
per hour should be 100 times the total weight of abalones in the tank. The level of dissolved oxygen in the seawater for spawners
should be over 4 ml/1. It is preferable to use an aerator and a water circulation device in order to have a high level of dissolved
oxygen in the conditioning water. It is better to control the light exposure time for spawners, however, the breeding tanks should
be kept in the dark.
• During the conditioning period it is important to provide good quality food on a regular basis.
• Most phaeophyceae, especially Laminaria and Undaria are a good food for abalones. The feed is given at about 20 % of their
body weight 2–3 times a week, and feeding rate should be regularly controlled. The daily feeding rate should be above 7 % until
the effective accumulative temperature for maturation reaches 800–1000 °C-days, otherwise maturity is delayed or may even
stop.
• The daily feeding rate is calculated as follows:
• where:
• F=feeding rate (%)F1=food suppliedF2=food left overC=compensation valueT=duration in daysW=abalone weightFrom the day
when the effective accumulative temperature for maturity is over 100 °C-days, the feeding rate drops below 2–3%. When rearing
spawners, the maturity of the operculum should be observed and the time of induced spawning should be expected according to
the effective accumulated temperature for maturity.
• At a seawater temperature of 7.6 °C, gonad growth and development begins. The temperature is called the biological zero point.
The effective accumulated temperature for maturity of above 1800 °C-days ensures a spawning rate of 98 %. Therefore, in order
to plan for the correct time to induce spawning, a management system should be established to control gonad conditioning and
maturation.
• With the rise of the effective accumulated temperature for maturity, more attention should be paid to the management of the
abalones. Fully matured abalones have a tendency to release their gametes when stimulated by a number of external stimuli.
Spawners should be matured for a further 80 days prior to a second spawning. Under such conditions, the number and quality of
released eggs are ensured.

17. BREEDING OF ABALONE Haliotis discus hannai
PROCEDURE:
Appearance of abalone
• Place the abalone in a glass tank to observe their behaviour. Allow them to creep on the bottom and walls of the
tank.
• A pair of tentacles protrude from the front end of the body. Observe the length and location of the tentacles and
touch their tips. Upon disturbance they disappear under the shell, however they reappear after a short interval.
These sensitive and chemotactic organs are protrusile.
• Immediately below the tentacles, the pair of eyes are visible. The eyestalk is named after its shape. Observe the
tentacles of the mantle protruding from beneath the shell. Identify the location and number of tentacles of the
upper foot. Count the number of brown spots on the upper foot.
• Observe the abalone moving its foot in an undulating and gliding fashion. Observe the abalone grazing on
benthic diatoms attached to the bottom of the holding tank, with the aid of its calyx lobe and radula. The calyx
lobe and radula are located on the anterior part of the body.
Shape of the abalone shell
• The abalone shell is shaped like an ear and although it is relatively thin it is strong. The shell length is about one-
fifth of the width. The spiral is very small. The soft part of the body is broad and wide and occupies most part of
the shell.
• As for the respiratory pores, only the last two to three stomas are perforated, while old pores are closed to form
bosses. The row of respiratory pores and bosses divides the shell into two parts, the upper part which is wide,
and the genital slope which has a rough surface and wave-shaped wrinkles.
• The abalone shell has a narrow and thickly laid growth-line which is commonly used to calculate the age of the
specimen. The outer surface of the shell is blue-brown or ash-brown in colour, however occasionally it may also
be red.
• The anterior end of the shell is wide and is of an ovate shape. The outer tip is thin, with a sharp edge, while the
inner tip is much thicker. The inner tip has a slimy edge.
• The inner part of the shell is blue-white or copper-white in colour, with a nacreous lustre.

18. Internal organs
• Remove the shell from the body by cutting the ligament. While separating the shell
from the body, take care to avoid injury to the intestine and other soft organs.
– Place the abalone on a dissecting plate, with its foot downwards and its head facing forward.
Pour seawater on the plate. Observe the overall body of the abalone and note the mantle
structure.
– Observe the shape of the tentacles, eyes and mouth located on the head at the anterior part
of the body. Identify the tentacles of the mantle and observe the feather-shaped gills and
anus. Observe the heart (left side), the spiral part of intestine (left side and posterior end),
and the liver (right side). Identify also the ramiform tentacles at the margin of the upper foot
and separate them for better analysis.
– When the above observations have been carried out, draw the organs on paper, making notes
on their location, size and colouration.
• Cut off the mantle with the aid of dissecting scissors in order to observe the internal organs.
– Observe the shape of the gills and locate the two auricles and atrium.
– Separate the gills and observe the ciliary movement under a dissecting microscope.
– Separate the muscular mouth and radula. Observe under microscope the pair of calyx lobe
and the long radula zone connecting the two lobes.
– The radula is a distinctive feature of all gastropods and it is commonly used for their
classification. It consists of numerous minute teeth shaped like knives. The radula is usually
long and broad in shape. An abalone with a shell length of about 80 mm has a 39 mm-radula
with 104 lines of teeth. The middle teeth are rather small with rounded tips and quadrangular
bases. The lateral teeth vary in shape while the marginal teeth resemble one another in
shape. They are sharp, narrow and relatively long. The uppermost tip is shaped like a surgical
spoon with a dentate edge.

19. • Observe the digestive organs of abalone: the gullet, stomach, intestine and anus.
– The digestive organ is in the soft tissue of the intestine capsule and therefore
rather difficult to identify its shape. Identify the mouth and anus.
– Then, using a dissecting needle, locate the digestive tube.
– The saccate V-shaped stomach can be seen next to the gullet. Microscopic
examination will show that the food in the stomach is mainly composed of
seaweed fragments.
– The vermiform appendix and liver are attached to the stomach and the cavity
connecting to the liver is placed at the curve of the stomach.
– The liver is located on the left side of the ligament. It is well developed and
relatively bulky.
• The liver is surrounded by the genital gland of the abalone.
• Remove a fragment of the tissue with the aid of a sharp scalpel and place it under a
microscope for detailed observation.
– The male has a milk-white genital organ while the female organ varies in colour
depending on the stage of development, fully matured organs being usually
greenish-brown in colour.
– The degree of maturity of the genital glands can be identified and classified as
follows:

20. Degree of maturity of the genital glands can be identified and classified
• Stage 1 (Granule stage) Granules are being formed but sperm and ovum cannot yet be
identified.
• Stage 2 (Green stage) The genital gland is not easily dissolved in seawater with many passive
and amorphous elementary particles.
• Stage 3 (Maturing stage) The genital gland becomes corpulent and most of the eggs are
globular in shape.
• Stage 4 (Pre-spawning stage) The genital product are released in small quantities.
• Stage 5 (Active-spawning stage) About 50 % of the genital glands are released.
• Stage 6 (Spent stage) Remaining genital glands can be seen with the naked eye. The mature
eggs and sperm are visible by microscopic examination.
– The measurement of maturity has a great significance in abalone culture.
Nervous system
• Its central nerve ganglion is placed around the mouth. A little scraping will expose the cerebral nerve
ganglion. Abalone also has a pair of nerve nodules (placed at the foot, intestine, etc.) and also a collection
of nerves connecting them.
• EXERCISE:
• After the above observations, follow the instructions below:
• Draw the appearance of abalone and make notes on its moving and feeding behaviour.
• Draw the shape of the abalone deprived of its shell.
• Remove the mantle and observe/draw the shape of the circulatory system, alimentary canal, etc.
• Observe the genital gland and identify its stage of maturity.

21. PREPARATION OF ADULT ABALONE
• PROCEDURE:
• 2.1 Selection of adult abalone from the sea
• The optimum size of abalone for spawning ranges between 7–9 cm.
– The best way to collect abalone is through the use of divers or hookmen. Well-trained divers can catch abalone with minimum injury to the specimen.
– The seriousness of the injury inflicted on the abalone will depend on the part of the body injured. Mortality increases when the abalones are injured on the
head, intestine sac, ligament or around the foot. Injury may be minimized when hooks are placed around the middle part of the abalone. If injury occurs, blood
flow may not be easy to control as it does not coagulate. The collected abalones are then placed into a holding tank for few days, after which the undergo a
second selection. After 3–4 days in the tank, injured specimens can be easily detected as the injured part usually becomes swollen and therefore visible. At this
stage the broodstock is selected from specimens which have no injury and appear healthy.
• The suggested period for catching adult abalone is between March-May and October-November when the water temperature is low. During these periods the
abalones are fairly inactive and can be easily caught. In addition, at higher water temperatures injuries inflicted during the catching process infect easily.
– At water temperatures above 20 °C, the injured parts become inflamed and serious signs of bacterial infection can be seen at water temperatures between
25–27 °C. At temperatures below 20 °C, bacteria growth is restrained while it increases at temperatures above 20 °C. Compared with that of healthy abalone,
the blood of injured abalone when tested will show impurities.
– Sulfathiazole is applied in the treatment of a wide range of diseases and contaminations. Animal sulfathiazole is acknowledged for its effectiveness, and is
applied in two ways: by reagent soaking and by surface application. When the abalone are soaked in the reagent, the concentration should be 5 % of the
filtered seawater. After 2–3 minutes in the reagent, the abalone should be exposed to the air for about 10–15 minutes. The efficiency of the medication
depends on the duration of the air exposure. When the temperature is high, exposure time should be shortened. The other method is the application of
sulfathiazole on the injured part with the use of a brush or a sprayer. Sulfathiazole may also be injected, but this is not recommended as the needle pore
causes bleeding. Treatment should be carried out for one week.
• 2.2 Transportation of abalone
• Frequent transportation is necessary in the culture of abalone. Adult abalone may be transported in buckets containing water or without water. Whichever the
method used, the abalone must be in a comfortable state so as to reduce mortality. Care must be given to ensure their firm attachment to the bucket or on the
attaching boards during transport.
• If the distance is short or if the quantity of abalone to be transported is small, they may be transported in buckets containing water. On the other hand, when abalone
are transported over long distances or the quantity is large, they are usually transported in containers without water.
– If the abalone are transported in buckets filled with water, frequent water changes and aeration are necessary to ensure proper water temperature and an
adequate supply of dissolved oxygen (not below 4 ml/l). A fine mesh knotless net or polyethylene sheet is usually laid over the bottom of the bucket to prevent
injury of the abalones when removed.
– In case more than a day of travel by train or truck is required, the abalone must be attached on the bottom or walls of an empty bucket, which should then be
covered by a seawater-wet medical cloth or fresh seaweed to provide the necessary moisture. The buckets should be protected from the sun or wind to
prevent drying and rise in temperature.
• The transported abalone should be moved to the rearing tank as soon as possible.
– Attention should be given to differences of temperature between the water in the bucket used for transporting, and that in the rearing tank. The difference of
water temperature between the bucket and the rearing tank should not be over 10 °C. If the difference in the water temperatures exceeds 10 °C, the mortality
rate will increase. At large temperatures differences the abalones should be gradually conditioned by increasing the temperature by 3–5 °C at intervals of 3–4
hours.
– Following the temperature conditioning period the abalone are transferred to tanks specifically designed for rearing abalone broodstock. An abalone with a
fleshy foot is usually considered to be a good broodstock and specimens with this characteristic are usually selected to eventually undergo conditioning.

22. BROODSTOCK CONDITIONING
• PROCEDURE:
• 3.1 Rearing facilities
• To induce maturation in adult abalones, the necessary biological and physical conditions should be met throughout the year,
and the rearing system itself should be properly maintained.
• Plastic drums with a holding capacity of 1–2 tons are often used in the rearing and conditioning of the abalone broodstock.
However, concrete tanks are sometimes used.
• Corrugated plastic plates (made of vinyl chloride) and/or V-shaped structures (usually made of cement, e.g. roof tiles) are
placed in the tanks for the abalones to attach on and seek protection. Abalone may also be matured in plastic netcages which
are convenient to maintain
• The netcage size should be for easy handling; they are usually square or oval. A one-ton tank with two netcages is
recommended as it is fairly convenient for all farm operations including feeding of adult abalone.
• 3.2 Rearing conditions
• Adult abalone sexually mature at water temperatures between 17–21 °C, however proper gonadal growth starts at a water
temperature as low as 7.6 °C.
• The above temperature minimum is considered the biological zero point in abalone farming, that is, at any temperature above
7.6 °C gonad maturation may be triggered. The sum of the effective accumulated temperature (EAT) is:
• (T - 7.6 °C)
• where:
• T = refers to the average rearing water temperature.
• Laboratory observations and trials indicate that the gonad grows at temperatures between 7.6–21 °C.
• The formula for the linear relationship between the rate of increase of the gonad index (Y) and water temperature (T) is:
• Y = 0.00597T - 0.04537 (T= ≤20 °C)
• At an EAT of 800 °C days, the reproductive organs mature, however the spawning rate still remains low. Spawning rate increases
up to 98% when an EAT of 1000 °C days is provided. Spawning time can be effectively planned when applying the EAT technique
to condition the broodstock.
• Laminaria and Undaria are a good feed for the adult abalone. Laminaria can be cultured and has a long rearing period.
– The average feeding rate should be 7 % above the normal for proper maturation of the abalone with an EAT between 800–1000 °C days. Below
this temperature the adult abalones take a long time to mature.
– The optimum feeding quantity is 30 % of the body weight; the food should be provided three times a week. At this time, the unconsumed
seaweeds should be collected in order to calculate how much food has been consumed. The average feeding rate per day can then be calculated.
As the abalones mature, feeding quantity should be reduced.

23. • During abalone maturation the amount of water change should be ten times the abalone's oxygen
consumption. Oxygen stability is normally guaranteed when 100 l/h per kg of abalone are supplied at the
rearing water temperature of 20 °C. The formula for calculating the rearing quantity of abalone by the amount
of water change is as follows:
• where:
• K= oxygen consumption by the abalone (ml/kg/hr)W= possible rearing quantityU= volume of inflowing waterV=
tank capacity (m3)C1= dissolved oxygen of inflowing water (ml/l)C= dissolved oxygen of outflowing water
(ml/l)K1= coefficient of dissolved oxygenK2= oxygen consumption except abalone (ml/l/hr)
• When the abalones are matured, a sudden change in the environmental conditions of the rearing tank may
trigger spawning. It is therefore, essential to carefully pay attention to maintain a constant environment.
– The light method is effective to stimulate spawning. Initially the rearing tank is irradiated by artificial light, with a
photoperiod of 12:12 hours. Two months before spawning, the day light may be reduced to nine hours in order to obtain
higher fecundity. Exposure to light does not greatly affect spawning if the abalones have a high EAT. As the abalone is a
nocturnal animal light exclusion is applied and no maintenance is conducted during this period.
– During the maturation process, tanks should be cleaned at least once a week. The rearing tank should be totally drained
to remove all faeces, and thoroughly washed with a strong jet of water.
– Abalone maturity should be investigated once the EAT of 800–1000 °C days is reached. Weekly investigations should be
carried out at higher water temperatures. The following formula is used to calculate abalone maturity:
• where:
• M =maturity (%)Ti =thickness of the middle part of the reproductive sac at the time of investigationTs =thickness of the
middle part of the reproductive sac before spawning. The thickness of the middle part of the reproductive sac prior
to spawning varies according to the size of the abalone and the prevailing environmental condition at the
culture site. Therefore, prior investigation is conducted a relation formula, to ease calculation, should be
formulated. In the case of the local (Korea DPR) abalone, the relation formula Y = -4.3 + 1.28 × is used to
measure the thickness of the middle part of the reproductive sac before spawning.

25. SPAWNING
• OBJECTIVE: To be able to perform the technique of controlled spawning.
• MATERIALS:
• Eight adult abalone
• Tanks for egg collection (20, 200–500 l)
• One UV-sterilizer
• Photo-electric colorimeter
• Microscope
• Glass tube (diameter 10–20 mm, length 500–600 mm)
• Light exclusion cloth
• PROCEDURE:
• A number of stimulating methods can be applied to spawn mature abalone.
• 4.1 UV light method
• The artificial spawning method should be selected taking into consideration the maturity of
adult abalone.
• During the stimulation process the female-male ratio should be 4:1. As spawning starts the
male and female abalone should be separated and allowed to continue the emission of the
genital product.
• An abalone with a mature gonad may release its gametes when the UV-sterilized seawater
stimulating method is applied. The volume of water to be supplied at the time of ultra-violet
exposure is 1/20 of normal sterilizing capacity. Ultra-violet lamps with various capacities and
with outputs between 15W-2KW are used. Low-pressure sterilizing lamps are more effective
as they emit a great amount of short-waves between 275–180 mm.
• The number of adult abalone to be used should be limited according to the number of eggs
required. The number of spawned eggs is about 1.5 million per 100 g of gonadal mass of a

26. Hatchery Phase
• Spat are grown up to 10 - 20 mm before being transferred from the hatchery
to the grow-out tanks.
• In farmed abalone, the hatchery process has four stages; broodstock, larvae,
settlement and weaning.
• The hatchery period from egg to 10-millimetre spat takes six months.
• Only superior abalone - both wild and bred - are selected for spawning and
kept in highly controlled environments.
• Abalone farm permits limit the number of wild broodstock that is allowed to
kept to 200.
After fertilisation, free-swimming larvae hatch within hours and develop
until ready to be transferred to a medium where they will attach and develop
into baby abalone called ‘spat’.
• As spat mature, their nutritional requirements change from a natural diet of
micro-algae to Abfeed, a formulated abalone diet.
• When they reach the size of 10 mm spat are strong enough to be transferred
to the grow-out environment.
• Some abalone farms may only transfer spat to the grow-out area when they
are 20 mm in size.

27. EGG FERTILIZATION AND EARLY EMBRYO HANDLING
MATERIALS:
• Fertilization and early rearing tanks (20, 100–500, 1000 l)
• Glass beakers (Diameter 10–200 mm, length 500–600 mm)
• Graduated cylinders (100, 250, 500 ml)
• Glass pipettes
• Simplified cell counter
• Microscope
PROCEDURE:
• Fertilization
• Fertilization rate is increased when it is carried out within one hour from egg
release. The quantity of semen required for fertilization is calculated based on its
concentration. The recommended egg density during the fertilization process is a
maximum of 40 eggs/ml, while the ratio of eggs and sperm should be 1:1000. At a
higher ratio, polyspermy usually occurs.
• Place the calculated amount of sperm into the bucket containing the freshly released
eggs and stir gently in order to facilitate dispersion of the sperm and aid egg
fertilization. Examine under the microscope the number of sperms sticking on the
membrane of one egg. Three to five sperm heads on one egg is an indication of
correct egg:sperm ratio. Too many sperms cause egg shrinkage and consequent
abnormal development. The normal rate of fertilization is above 95 %.

28. Egg washing
• Successfully fertilized eggs sink to the bottom of the tank. The sinking speed of the eggs is 2 cm/sec. Unfertilized and
abnormal eggs sink two to three times slower than the fertilized ones.
• The upper water layer is removed by suction or by slightly tilting the tank to one side after the eggs have sunk to the
bottom.
• This procedure is carried out to remove unwanted matter such as abnormal and unfertilized eggs. When drawing out the
water, at least 15 cm from the bottom should be left in order the prevent the eggs from being sucked out or damaged.
• At this stage freshly filtered and sterilized seawater is added to the tank containing the developing embryos. The newly
added seawater should have the same temperature as water and the fertilized eggs should soon start floating uniformly.
• When pouring the additional seawater, attention should be taken not to pile the eggs on one side of the tank as more than
one egg layer may induce some eggs to develop abnormally.
• The eggs should be washed five to six times until they hatch.
• If fertilized eggs are piled on the bottom of the tank for more than three hours, their growth is affected as oxygen supply
is generally not sufficient.
• Care should be taken when washing the eggs as handling may affect the subsequent survival of the abalone larvae.
• Examine the developing embryos under the microscope. Observe normal and deformed embryos as well as the
unfertilized eggs. Measure the diameter of the normal growing eggs and calculate the rate of fertilization.
• When the eggs have been thoroughly washed add fresh seawater.
• At this stage fill a 100 ml graduated cylinder by dipping it in five different places of the tank, to be fixed under formalin.
• When fixing with formalin, the upper 15–20 ml in the cylinder is removed after the eggs have sunk to the bottom and the
same volume of formalin added.
• The water in the cylinder is stirred and a 0.5–1.0 ml sample is collected by using a pipette for observation under the
microscope using a simplified cell counter.
• At this stage the number of normally developed, unfertilized and deformed eggs can be observed and counted.
• The count is carried out five times to obtain the average value.
• The ratio of successful egg fertilization and the ratio of normal egg development can be calculated as follows:
• Ratio of fertilization (%)
• Ratio of normal cleavage (%)
• It is important to maintain a constant water temperature during egg cleavage, as even small differences may cause
abnormal egg development. The most suitable temperature level for culturing abalone eggs is above 30 °C.

29. REARING OF FREE-SWIMMING LARVAE
MATERIALS:
• Rearing tank (1000 l)
• Cotton gauze for larval collection
• Microscope
• Graduated cylinders (250, 500 ml)
• General larval rearing equipment
PROCEDURE:
• The free-swimming period of larvae is usually between 4–10 days, however this may vary under specific conditions.
Larval appearance
• In rearing free-swimming larvae it is important to provide the appropriate environmental conditions to reduce to the minimum the free-
swimming period. Newly hatched larvae swim freely with the help of the velum and move to the upper layers of the rearing water as they
are actively phototrophic.
– Study the activity of newly hatched larvae under the microscope. The health condition of larvae can be judged from their appearance
(i.e. body shape), mobility and ability to swim vertically up the water column.
– Larvae which swim actively, moving clockwise or counterclockwise by the constant movement of the velum, and normal in shape and
size tend to grow and perform well.
– Observe larvae with a poor and weak activity. These specimen are usually abnormal in shape or small in size.
Rearing parameters
• Transfer all swimming larvae in the upper layers of the water column to the rearing tank by siphoning with a hose.
– A larval rearing density of 300/l usually causes no particular problem, however in case of higher densities (1000/l) good management
should be ensured, particularly with regard to water change, oxygen supply, etc. Rearing density is closely related to the quality of the
rearing equipment and knowledge of management techniques.
– Constant water temperature is an important factor in the rearing of free-swimming larvae.
• Water temperature suitable for larval growth and survival is around 20 °C.
• Salinity should be above 30 ‰.
• The amount of dissolved oxygen (DO) in the rearing water should be more than 4 ml/l. Oxygen deficiency lasting for half an
hour causes the larvae to sink to the bottom of the tank due to a weakened state. Air should be supplied regularly to maintain
the DO at the standard value.
• The volume of water to be regularly changed varies according to the larval rearing density. At densities above 1000/l, the entire
water volume should be changed once every 6–8 hours, while at 300/l, the entire water volume should be changed daily.
– Observe on a regular basis the developmental stages of the larvae and note their activity, shape and mobility as well as calculate the
survival rate.

30. REARING OF JUVENILE ABALONE
MATERIALS:
• Rearing tank
• Rearing boards
• Microscope
• Cotton gauze
PROCEDURE:
Major rearing technical and management problems
• The physiological and morphological changes in the abalone larvae, such as
the growth of the foot and the appearance of the tentacles, take about four
days under optimum culture conditions. During this period the larvae
search for a suitable surface to initiate their benthic life. If they are unable
to locate a bio-chemically or physically suitable surface, they will continue
their planktonic life, and the larval period may last up to 10–20 days.
• When a suitable surface is found the larvae move from the free-swimming
to the creeping stage. This process is timed with the disappearance of the
velum. After several metamorphic stages, they become juvenile abalones.
• The major management and technical problems at this stage involve the
provision of rearing conditions suitable for survival and growth after
metamorphosis.

31. Preparation of rearing boards
• Plastic materials such as polyethylene, polyesterol, acrylic, and PVC are commonly used for
manufacturing the rearing boards.
• The size and shape of the boards differ according to the rearing facilities available, however
wave-shaped plastic plates are usually used. The size of a rearing board is about 30×30 or
40×40 cm. The boards are assembled in frames that hold 10–20 boards, arranged at 3–5 cm
intervals in order to facilitate their handling.
• The provision of a biologically suitable surface to the benthic larvae is an important factor in
terms of their survival and growth. In addition, live food of suitable size and appropriate
density should be cultured on the surface of the rearing boards in order to provide nutrients
to the creeping larvae.
– Properly assembled rearing boards should be placed in the larvae rearing tank which should be in the dark
or not directly illuminated.
– A continuous flow of filtered seawater should be supplied for about ten days. Particles above 10 um in size
should be removed through filtration, while protozoans and bacteria of smaller size should be left in the
filtered seawater. When the rearing boards are in contact with the seawater for about ten days they
become coated with a layer of microorganisms at an appropriate density. Boards with such a surface
induce the abalone larvae to set and metamorphose. These also provide good feeding conditions to the
creeping larvae during the first 10–20 days. The distance between single microorganism cells on the board
should be in the range of 10–50 um, which provides the suitable density.
– Place the diatom fluid containing 1–2 species of Navicula, of less than 10–20 um in size, in the rearing tank
a day before introducing the larvae. The diatoms successfully become attached to the rearing boards
when the water is static for more than 8 hours.
– The water temperature should be between 19–21 °C throughout the rearing period. In addition, ammonia
should be below 50 ppb, while pH and salinity above 7.9 and 30 ‰ respectively. The level of DO should be
maintained in the range of 70–100 % of saturation. The level of nutritive salts per litre of rearing water
should be as follows:
Nitrogen=5 ug - nitrogen atom weightPhosphorus=1 ug - phosphorus atom weightSilicon=5 ug - silicon atom weight

32. Rearing of larvae
• Collect and transfer free-swimming larvae at the point of metamorphosis,
into the rearing tank in which the diatom coated boards have been placed,
and adjust the density to about 300 larvae/l.
• At this stage the rearing water should be static, as the time taken by the
larvae to settle on the boards ranges between few hours to one whole day.
• Following the completion of metamorphosis into a creeping larvae, the
water should be regularly changed and aeration supplied.
– The water should be changed three times a day, in order to maintain its quality
as described earlier.
– It is preferable to supply air at intervals of 15–20 minutes rather than provide a
continuous supply.
• Between 10–20 days after setting, the abalone larvae begin to feed on
diatoms about 20 um in size.
• If feed deficiency on rearing boards is determined through observations
under the microscope, the above-mentioned diatom fluid should be added
and the water allowed to be static for about eight hours.
• Diatom propagation in the rearing tank takes place when the light intensity
is about 3000 lux.
• Attention should also be drawn to the biological management of the rearing
tank.

33. – The larvae on the rearing boards grow to about eight times in biomass in the
first ten days and accordingly produce more excretion.
– Ammonia and carbon dioxide are also produced from the dead larvae and
decomposition of unconsumed food.
– Ammonia is detrimental to the larvae even at a concentration as low as 50
ppb.
– Undesirable water quality causes larvae to be less resistant to the intrusion
of bacteria and other pathogens.
– The larvae thus tend to grow rather slowly.
– Oxygen deficiency may occur as a result of bacterial growth on dead tissue
and excretion.
– The removal of contaminants is carried out by regular water change and
proper air supply.
– On the other hand, contamination at the bottom and on the walls of the
rearing tank should be removed with the aid of a hose or washed manually,
after having removed the rearing boards.
– Light intensity should be regulated in order to enhance diatom growth which
is responsible for the assimilation of ammonia, carbon dioxide, etc., as well
as being the main food for the abalone larvae.
– Rearing yields are usually high when the density of bacteria remains below
100 cells/ml.
– The level of bacteria is usually regulated by treating the rearing water with
an ultra-violet

34. INTERMEDIATE REARING
MATERIALS:
• Netcage for intermediate rearing (60x80x30 cm)
• Rearing boards
• Pair of scales
PROCEDURE:
Rearing facilities and conditions
• Land-based intermediate rearing facility
– Abalone juvenile are reared in netcages which are placed in land-based cement tanks coated with
synthetic resin or waterproof cloth. Rearing can be carried out by using a water circulation or a flow-
through system, depending on the source of seawater supply.
– A rearing farm should be supplied with seawater with the following quality parameters:1)ammonia=<50
ppb2)pH=>7.93)salinity=>30 ‰4)DO=70–100 % saturation.
• Sea-based intermediate rearing facility
– A sea-based intermediate rearing facility usually consists of a series of floating netcages located in
protected sites and kept in position by a system of floats, ropes and weights. When using the above facility
it is important to pay particular attention to the selection of the site, as the entire rearing facility may be
destroyed and lost during bad weather conditions.
Intermediate rearing
• Rearing density. The rearing density varies according to the initial size of the abalone
juvenile, as well as on the type of the rearing device. However, it is normal to stock 5 kg and
3 kg per m3 in land- and sea-based facilities, respectively. Higher stocking densities usually
cause the growth rate of abalone to drop, as well as the piling of abalones on top of one
another, which then need to be manually separated. When the mass of the cultured
abalones duplicates, thinning should be carried out by dividing the abalones in half. Thinning
is easily achieved by removing half of the rearing boards and replacing them with new ones
on which the abalone will soon settle.

35. • Feed supply.
• The amount of feed supplied varies according to the size of the abalone
juvenile as well as on the prevailing seawater temperature.
• Feeding rate increases with increase in water temperature and it is usually
high among small abalone specimens.
• The food is usually provided at intervals of 5–10 days, and the amount
should be twice the actual feeding capacity of the stocked abalones.
• Major seaweeds fed to abalone include species such
as Laminaria, Undaria and Ulva. Seaweeds used as feed should be cut into
small pieces the size of the abalone, cleaned and removed of their roots
and fouling organisms.
• Abalones of different sizes are usually fed as follows:
– Specimens measuring 6–10 mm in shell length are fed with finely
chopped Ulva spread over the bottom of the rearing facility, as well as with
diatoms attached on the rearing boards.
– Young Laminaria and Undaria plants mixed with a certain amount of Ulva are
fed to abalone 10–13 mm in size.
– Abalones above 13 mm are fed with Undaria and Laminaria. At this stage,
attention should be paid to the rate and feeding quantity, as leftover feed easily
becomes fouled.

36. • If intermediate rearing is carried out on land-based facilities, abalone
faeces and leftover feed should be removed regularly.
• Cleaning of the rearing facilities should also be carried out on a regular
basis.
• When the seawater temperature is above 20 °C, cleaning should be done
every 6–7 days while once every 10–15 days at temperatures below 20 °C.
• Fouling organisms on sea-based rearing installations should be removed
as they hinder water flow.
• Netcages should be regularly cleaned or changed at the time of feeding.
• On land-based rearing facilities, a 30 mm abalone may double in size
within one year, while on sea-based installations, abalone growth occurs
mainly from May to November.
• During the intermediate rearing period, the major factors influencing
growth rate are water quality, mechanical disturbance (eg. wave action in
sea-based facilities), excessive rearing density or unsuitable rearing
structures.
• It is important to bear in mind that regular investigation on environmental
conditions and on the performance of the abalone is needed.
• The survival rate of abalones during intermediate rearing is usually about
80 %, attaining a shell length of 30 mm.

37. Grow-out Phase
• Abalone is kept in oyster net baskets suspended in tanks, through which
seawater is circulated and fed an artificial diet, which is specially formulated
for the species. Abalone diet is often supplemented with fresh seaweed or
kelp.
• Abalone tanks are cleaned weekly.
• The optimal temperature range for abalone is between 16°C and 18°C.
Lower temperatures may slow down growth, while higher temperatures may
hinder larval development.
• Water is regularly tested and monitored for temperature, pH, oxygen and
ammonia levels.
• Throughout the grow-out phase, abalone is regularly sampled to check on
their weight and then size graded, thinned out and moved, to improve
stocking density.
• This allows for even and consistent growth. Stocking density may depend on
tank size and management practices.
• Typical survival rates for abalone are 86% over 45 months in recirculating
cage (or flow-through) systems and 30% (after seeding) in a ranching
system.
Depending on the farm's growth rates, animals may reach market size
between 36 – 50 months.

38. Harvesting Abalone
• Abalone is harvested according to the size needed for a
specific order.
• Agents or customers can order very specific sizes such
as 250 kg of 70 - 90 g and 100 kg of 150 - 160 g.
• The requested size usually has something to do with a
dish the restaurant is preparing or portion size per
person.
• Abalone is graded to ensure the right sized animals
fulfil the order.
• These animals are then conditioned by placing them in
very clean filtered seawater for a few days.
• This helps them recover from the stress of the grading
and helps them survive the airfreight to the Asian
markets.

39. Nutritional information, diet information and
Calories in Abalone, fired

40. References
• https://www.fao.org/3/AB731E/AB731E01.htm#chp1I
• https://www.fao.org/3/AB731E/AB731E03.htm
• https://southafrica.co.za/abalone-farming-
systems.html#:~:text=Systems%20used%20in%20the%20farming,Fisheries%20(DAFF)%20in%202018.
• https://youtu.be/kVTe5wyoM6E
• https://www.asc-aqua.org/aquaculture-explained/how-asc-can-help-you-eat-seafood-responsibly/farming-and-eating-abalone-
responsibly/
• https://www.fitbit.com/foods/Abalone+Fried/21419
• https://www.google.com/search?q=abalone+nutritional+composition&sxsrf=ALiCzsYlCbROb5_MisubPal5u3cN2TOubA:16617
64115193&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiHiaXe2ev5AhX_TmwGHWOYDtsQ_AUoAXoECAEQAw&biw=1
366&bih=625&dpr=1#imgrc=Kn4ipAeWxvXIuM
• https://www.google.com/search?q=abalone+life+cycle&tbm=isch&ved=2ahUKEwiK56rY2uv5AhV0ktgFHXpkCMsQ2-
cCegQIABAA&oq=abalone+life+cycle&gs_lcp=CgNpbWcQAzIFCAAQgAQyBQgAEIAEOgQIIxAnOggIABCABBCxAzoGC
AAQHhAIOgQIABAYUKMKWOIqYLQxaABwAHgAgAGOAYgBlgmSAQQxMS4ymAEAoAEBqgELZ3dzLXdpei1pbWe4A
QPAAQE&sclient=img&ei=E4MMY8qRCPSk4t4P-
sih2Aw&bih=625&biw=1366#imgrc=Yn2JhvJrxbLdIM&imgdii=rTlMpfSbyobegM
• https://www.google.com/search?q=abalone+life+cycle&tbm=isch&ved=2ahUKEwiK56rY2uv5AhV0ktgFHXpkCMsQ2-
cCegQIABAA&oq=abalone+life+cycle&gs_lcp=CgNpbWcQAzIFCAAQgAQyBQgAEIAEOgQIIxAnOggIABCABBCxAzoGC
AAQHhAIOgQIABAYUKMKWOIqYLQxaABwAHgAgAGOAYgBlgmSAQQxMS4ymAEAoAEBqgELZ3dzLXdpei1pbWe4A
QPAAQE&sclient=img&ei=E4MMY8qRCPSk4t4P-sih2Aw&bih=625&biw=1366#imgrc=rTlMpfSbyobegM&imgdii=T3578-
wA8QoohM
• https://www.google.com/search?q=abalone+life+cycle&tbm=isch&ved=2ahUKEwiK56rY2uv5AhV0ktgFHXpkCMsQ2-
cCegQIABAA&oq=abalone+life+cycle&gs_lcp=CgNpbWcQAzIFCAAQgAQyBQgAEIAEOgQIIxAnOggIABCABBCxAzoGC
AAQHhAIOgQIABAYUKMKWOIqYLQxaABwAHgAgAGOAYgBlgmSAQQxMS4ymAEAoAEBqgELZ3dzLXdpei1pbWe4A
QPAAQE&sclient=img&ei=E4MMY8qRCPSk4t4P-sih2Aw&bih=625&biw=1366#imgrc=b0S5WnqhZ9TKaM
• https://www.google.com/search?q=abalone+life+cycle&tbm=isch&ved=2ahUKEwiK56rY2uv5AhV0ktgFHXpkCMsQ2-
cCegQIABAA&oq=abalone+life+cycle&gs_lcp=CgNpbWcQAzIFCAAQgAQyBQgAEIAEOgQIIxAnOggIABCABBCxAzoGC
AAQHhAIOgQIABAYUKMKWOIqYLQxaABwAHgAgAGOAYgBlgmSAQQxMS4ymAEAoAEBqgELZ3dzLXdpei1pbWe4A
QPAAQE&sclient=img&ei=E4MMY8qRCPSk4t4P-
sih2Aw&bih=625&biw=1366#imgrc=egfjq2lCc9aCOM&imgdii=l9BSdm2SBTKsBM
• https://www.google.com/search?q=abalone+taxonomy&tbm=isch&ved=2ahUKEwjqqKGt2-v5AhWhgWMGHRkJDt8Q2-
cCegQIABAA&oq=abalone+taxonomy&gs_lcp=CgNpbWcQAzIECAAQGDoECAAQQzoFCAAQgAQ6BggAEB4QBVCuFVje
QGC0RGgCcAB4AIABYYgBuAeSAQIxMZgBAKABAaoBC2d3cy13aXotaW1nuAEDwAEB&sclient=img&ei=xYMMY6qyD
qGDjuMPmZK4-A0&bih=625&biw=1366#imgrc=2Ir-SR4TAx86zM
• Integrated Taxonomic Information System - Report,
https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=69497#null