breeding of seabass

1. Breeding & hatchery
management
of
seabass

3. v
TAXONOMY
•
Phylum: Chordata
Class: Pisces
Order: Perciformes
Family: Centropomidae
§
S.N. - Lates Calcarifer (Bloch, 1970)
C.N. – Asian Seabass
Distribution – Indo-pacific region
§
S.N. – Dicentrachus labrax
C.N. – European Seabass
Distribution - Atlantic sea

4. v
Identifying characters :
A. Elongate and compressed body, with a deep
caudal peduncle.
B. Head is pointed with a concave dorsal profile ,
becoming convex in front of the dorsal fin.
C. Mouth large, slightly oblique and the lower edge
of the pre-opercle is serrated, with a strong spine.
D. Adults are greenish or bluish above and silvery
below.
E. Eyes are bright pink, glowing at night.

5. v
Food and feeding :
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Highly predatory, adult feeding on small fish and
crustaceans
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Juveniles are omnivorous.
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Fry feed on zooplankton, while fingerlings prefer
small crustaceans, worms, mollusks, etc
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carnivorous and highly predatory, cannibalistic

6. q
Euryhaline fish
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Living in brakishwater esturies and also in
freshwater.
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Also called as giant perch
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High demand, high market value.
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For spawning , they migrate to the sea and
juveniles migrate back to the brakishwater for
feeding and growth.

7. Reproductive Biology
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Protoandrous hermophrodite
Male Female
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Male - slender body
abdomen does not bulge out
slightly curved snout
milt oozes out on slight pressure on abdomen
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Female – soft belly
abdomen bulge out
a red pink papilla also extends out at the
urinogenital aperature.

11. Spawning Habits
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Year round spawner with peak season being from
April-August.
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Protracted Spawner – Eggs released in batches.
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Spawns 3 times in a season at an interval of 15
days
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Natural Spawning ground – Sea near the mouth
of big rivers and lakes
Water depth 5-10m
salinity 28-30 ppt
Water temperature 27-34 c

12. q
Spawning usually takes place 3-7 days after full
moon and new moon.
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Spawning time – 6 P.M. – 11 P.M.

14. Brood stock Maintainance
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2-6 year old fish having an average wt. of 3-5 kg shall be
useful .
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Brood fish can be collected from
fish farm
natural waters ( wild brood stock )
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Brood fish reared in separate earthen tanks / cages /
concrete tanks.
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Wild brood stock are treated with antibiotic @ 20mg/kg
of fish by injection or in 2 ppm medium for dipping for
24 hours.

17. Floating cages
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popular in Indonesia
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Size – 5x2x2 m. Or 10x10x2 m
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Stocking rate- 1 fish/m3 of water
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Polythene net having mess size 4-8 cm attached to
pipes or wooden form of cage.
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float – styroform drum
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Anchored in calm bay area

20. Concrete tanks
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size – 5x10x2m or 10x10x2 m
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Stocking rate – 1 fish / 2 m3 of water
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30% daily water replacement
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Feeding rate – 5% of body wt. with trash fish
Feeds and feeding
§
Brood fish are fed once daily with fresh fish given at the
rate of 5% of total biomass. Trash fish should be clean
and fresh.

22. Pre-spawning tank
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reared for 2 months before spawning operation
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Male : Female : : 1 : 1
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Feeding reduced to 1% of body wt. fed once a day
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fish should be active
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fins and scales should be complete
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free from disease and parasite
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free from injury or wounds
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males and females of similar size groups are preferred
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changing the water about 50–60% daily.
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spawner should be at least 4–5 kg in body weight and
should not be less than 3 years old

23. Assessing the stage of ovarian maturation
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a catheter of 1.2 mm diameter is used.
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It introduced into oviduct through urinogenital
aperature.
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sucks the egg and taken on a slide for
measurement of diameter of egg.
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Diameter 0.4-0.5mm i.e. female ready for
injection

26. Seed production :-
There are 2 methods of seed production.
A. Stripping and artificial fertilization
B. Induced Spawning
A. Stripping and artificial fertilization
a) stripping of mature fishes
§)
Egg collection - Female fish
§)
Milt collection – Male fish

28. b) Artificial fertilization :- Dry method
Egg collected in container having no water
Milt is added in it
Mixed by means of quill feather for 5 min
Filtered Sea water added
Allowed undisturbed for 5 min
Fertilized eggs are transferred to incubator for hatching.

30. B . Induced Spawning
a) Hormonal therapy :-
1. HCG with carp pituitary :-
§)
Two intraperitonial injections at the base of pectoral fin.
First injection 50 IU HCG and 0.5 P.G./Kg body wt.
12 hours duration
Second injection 100-260 IU HCG and 1.5-2 P.G./Kg
body wt
Within 10-12 hr. Spawning occurs
Repeatedly spawn over a period of 3-5 days
§
Single Spawner : - 2-17 million eggs

32. 2. Puberogen :- 63%FSH + 34% LH
•
Two intramuscular injections
First Injection
50-200 IU/kg. wt. of Female
20-25 IU/kg. wt. of Male
48 hr. duration
Second Injection (if no spawning
occurs)
Dose Double for Female
20-25 IU/kg. wt. of Male
Within 12-15 hr. Spawning Occurs
Spawn within 36 hours

35. B. Environmental Manipulation
Based on field observations and analysis of natural
phenomena that occur during spawning period of
seabass, techniques were developed to stimulate the
fish to spawn in captivity.
The following steps are necessary:
§
changing the water salinity to simulate fish migration
§
decreasing the water temperature to simulate the
decreased water temperature after rain
§
lowering and subsequent addition of fresh seawater
to the tank in order to simulate the rising tide
§
follow the moon phase.

36. q
Initially, the salinity of water in pre-spawning tank is
prepared at 20–25 ppt before stocking the selected spawners.
After stocking, 50–60% of water is changed daily until 30–32 ppt
is reached. This will take about 2 weeks.
q
This will simulate the migration of fish from its growing
grounds to the spawning grounds.
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Constant monitoring of fish is required to detect pre-
spawning behavior. When the fish is observed to display its
silver belly, this is an indication that it is ready to spawn.
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The female fish separate from the school and cease to feed
one week prior to spawning. Two or three days before the new
moon or full moon, as the female approaches full maturity,
there is an increase in play activity. The ripe male and female
swim together more frequently near the surface as spawning
time approaches.

37. q
At the beginning of the new moon or full moon, the water
temperature in the spawning tank is manipulated by reducing
the water level in the tank to 30 cm deep at noon time and
exposing to the sun for 2–3 hours. This procedure increases water
temperature in the spawning tank to 31–32°C. Filtered seawater is
then rapidly added to the tank to simulate the rising tide. In
effect, the water temperature is drastically decreased to 27–28°C.
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The fish spawn immediately the night after manipulation (1800–
2000 hours) or if no spawning occurs, manipulation is repeated
for 2–3 more days, until spawning is achieved

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Incubation and Hatching
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Fertilized Eggs – Floating
transparent
0.78-0.8mm in diameter
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Unfertilized Eggs -- Opaque
sink to the bottom .
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single spawning – 0.75-1.5 million eggs.
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For collection of eggs , Seine net used which is soft and fine
meshed having mesh size 0.4-0.5mm.
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For hatching fibre glass tank or hatching jars are used in which
gentle aeration is done in the jar.

43. Eggs are collected in the morning
Dip them 5 ppm acriflavine
Transferred to the sea water .
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Density of eggs in hatching jars can be 1200 nos / liter
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Hatching occurs 17-18 hours after fertilization at 26 c – 28 c and
32-33 ppt .

44. v
Larval Rearing
§
Length of newly hatched larva :- 1.5 mm
§
Transferred to larval rearing tank
stocking Density – 30 nos / litre or 90 nos / litre
§
The rearing tanks are commonly fabricated from plastic,
fiberglass, wood or concrete. A typical larval rearing tank is
rectangular in shape and located outdoor. Its volume ranges from
8–10 tons (7 × 1.2 × 1m or 10 × 1.5 × 1m). The tanks are usually
protected from strong sunshine and heavy rains by a roof tile
cover. The usual stocking density for newly-hatched larvae in
rearing tank is between 50–100 larvae/liter.

45. q
Good quality seawater at 30–31 ppt is required for larval rearing.
Water temperature is also important and should range from 26–
28°C to promote fast growth of larvae.
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Larval tanks are prepared one to two days prior to the transfer of
newly-hatched larvae.
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Filtered seawater are added to the tanks and very mild aeration
is provided.
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After stocking, unicellular algae (Tetraselmis sp.
or Chlorella spp.) are added to the tank and maintained at a
density of 8–10 × 103 or 3–4 × 104 per ml for Tetraselmis sp.
and Chlorella spp., respectively.
q
These algae serve a dual purpose: as a direct food to the larvae
and rotifer and a water conditioner in the rearing tank.

46. q
The following day after stocking, the bottom of the larval rearing
tank should be cleaned and everyday thereafter. This is done by
siphoning unfertilized eggs, faeces, dead larvae and uneaten food
accumulating on the bottom of the tank.
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About 20% of tank water is changed daily for the first 25 days of
the rearing period, then increased to 40–60% per day for the
remaining culture period.

47. Rearing of spawn in cement Tank

48. Grading
In the rearing of seabass fry under confined conditions, the competition
among the individuals for feed and space results in uneven growth of the
fish especially if the stock is poorly managed. Heaavy mortalities will also
occur due to cannibalism and stress on small or weaker fry. Since seabass is
a voracious carnivore, proper grading should be done to avoid cannibalism.
The graded fish must be reared separately.
Cannibalism in seabass larvae is distinctly rampant from the time the
larvae starts to feed on Artemia (day 10 larvae). Grading is usually done a
week after the fish started to feed on Artemiaand every week thereafter.
Grading trays used are normally made of plastic basin with many holes
bored through the bottom, or made of netting with a wooden frame
Each tray has a specific hole or mesh size to allow specific size of fish to
pass through. The size of the hole/mesh of netting in each vessel varies
from 0.3–10 mm. Fish are placed in the trays which are floated in the
newly prepared larval rearing tank. The smaller size fish can pass through
the hole to the new tank. The remaining fish in the vessel are transferred
into another tank and likewise graded with the use of a bigger hole or
mesh tray. This procedure sorts out fish to several sizes and simplifies
management

49. Size Grading of Larvae
Sea bass larvae are highly cannibalistic.
This reduces the percentage of survival.
Among a population of fry some grows
faster and these are called “shooters”.
These shooters consume small size fry.
To reduce cannibalism, the fry are
segregated size wise in three categories-
large, medium and small.
‘Fry sorter box’ is used for segregation.

56. References :-
Ø
Manual on hatchery production of seabass , FAO
Ø
MANUAL FOR SPAWNING OF SEABASS, LATES
CALCARIFER, IN CAPTIVITY , FAO
Ø
REPORT ON THE TRAINING COURSE ON SEABASS
BREEDING AND CULTURE, FAO
Ø
SEAFDEC/AQD Institutional Repository (SAIR)
Ø
IMPROVED HATCHERY TECHNOLOGY FOR ASIAN
SEABASS Lates calcarifer - CIBA manual no. 180
Ø
Seed production of Finfishes and shellfishes – P.C.Thomas

57. created by :- Amit Waghambar Jadhav
B.F.Sc.
College of Fishery Science Udgir