Mud crab

1. MUD CRAB
Submitted by:
Kumar Kashyap
M. Tech Marine Biotechnology
Second Semester
NCAAH

2. INTRODUCTION
 Scylla serrata (mud crab or mangrove crab or black crab)
 Economically important species of crab - estuaries and
mangroves of Africa, Australia and Asia
 The shell colour - deep, mottled green to very dark brown.
 Classification
 Kingdom : Animalia
 Phylum : Arthropoda
 Subphylum : Crustacea
 Class : Malacostraca
 Order : Decapoda
 Family : Portunidae
 Genus : Scylla
 Species : S. serrata

3.  Distribution
 Naturally Indo-Pacific region
 Found from South Africa, around the coast of the Indian
Ocean to the Malay Archipelago, as well as from
southern Japan to south-eastern Australia, and as far east
as Fiji and Samoa
 Introduced to Hawaii and Florida

4.  Ecology
 A study on tidal flats in Deception Bay in Queensland
 Juvenile crabs (20–99 mm or 0.8–3.9 inch carapace width) -
mangrove zone, remaining there during low tide
 Sub-adults (100–149 mm or 3.9–5.9 inch) migrated into
the intertidal zone to feed at high tide and retreated to
subtidal waters at low tide.
 Adults (150 mm or 5.9 in and larger) were caught mainly
below the low tide mark, with small numbers captured in the
intertidal zone at high tide.
 These crabs are highly cannibalistic in nature; when crabs
undergo moulting; other hard-shelled ones sometimes attack
the moulting crabs and devour them.
 The females can give birth to a million offspring which can
grow up to 3.5 kg (7.7 lb) in size and have a shell width of up
to 24 cm (9.4 in) wide.

5. MUD CRAB FARMING
 Huge demand and price in international market. Tasty
 Import – currency by exporting
 Main benefits –
 Low labour cost
 Low production cost
 Grow faster
 By proper care more can be earned from crab farming
than shrimp farming

6.  Mud Crab Farming Methods
 Two systems can be used: grow out farming and
fattening systems
 Grow out system
 Young crabs are raised and grown for a certain period of 5 to
6 months till they reach marketing size and weight
 Pond based – pond size depend on the production type.
Generally 0.5 to 2 hectares
 Proper bunds and tidal water exchange is must.
 Small sized ponds more suitable. Because easily maintained.
But a suitable fence is required
 Large size ponds – natural condition are prevailing,
strengthening is necessary along the area.
 Juvenile wild crabs (10 – 100 gm) are stocked
 Depending on size and available facilities – 3 to 6 months
 Commercial production with supplementary feeding – 1-3
crabs per square meter.

7.  Fed with low cost fish, shrimps, small sized crabs etc
 Rotted fish, innards of birds, animals from slaughter house,
can also work
 Daily feed = 5% of their body weight
 Regular sampling
 Small pipes are kept to avoid cannibalism
 Within 3 to 5 months they reach marketing size
 Fattening System
 Pond size – 0.025 to 0.2
 Raising soft shelled crabs for a certain period until their
exoskeleton gets hardened
 To five times more value in the market
 Less time, process is very profitable
 Can be done be 2 systems: Fattening in pond, Fattening in ponds
or cages

8.  Fattening in pond:
 Pond size 0.025 to 0.2 hectare size and depth 1 - 1.5 m
 Pond preparation – draining the pond water, sun drying, add
sufficient quantity of lime
 Fence around the pond for fattening purpose crabs have a
tendency to escape by making hole and digging the soil. The inlet
areas were reinforced with bamboo matting inside the bund
 Soft crabs from local fisherman or crab merchants, in morning
 1-2 per square meter stocking density
 Divide the pond into different compartments according to the size
of crabs if it is big sized
 Male and female crabs separate - good results and reduce mutual
attacks and cannibalism
 Depending on location and crabs availability 8 to 12 fattening
cycles can be done in a year
 crabs weight between 300 grams to 500 grams has high demand
and value
 Crabs are collected and sold when they reach the optimal
marketing weight. Always when they are shelled. High profit.

9.  Fattening in Pens or Cages
 Pens, floating net cages, and bamboo cages in shallow estuarine
waterways and inside large shrimp ponds with good tidal water
influx and in tanks
 Bamboo splits, netlon or HDPE as netting material
 3 m * 2 m *1 m (3 m long, 2 m wide and 1 m height) is ideal cage
size for crab fattening
 Arrange the cages in a row so that you can easily feed and
monitor the crabs
 Stocking density of 10 crabs per square meter in cage and 5 crabs
per square meter in pens is ideal
 Fattening in cages or pens is only used in small sale production
 For commercial purpose, fattening in ponds is perfect and more
profitable
 Fattening system is more profitable than grow out system and
has many advantages. Grow out crab farming system takes
more time than fattening system. Also fattening system is
very popular to the farmer as it takes less time and highly
profitable.

10.  Water
 Water quality plays an important role in the production of
crabs. Change water occasionally if possible or apply proper
medicines or chemicals.

11.  Feeding
 crabs need 5-8% food of their body weight
 cost trash fish, chicken waste, animal innards collected form
slaughter house, brackish water clams
 twice a day
 Major part of the total feeds should be given during evening
hours

12. MUD CRAB HATCHERY MANAGEMENT
 Highly preferred commodity in the International Seafood
market
 Over exploitation of this natural resource from the wild
has resulted in the stagnation of fisheries production of
this species across the world including India
 The Mud Crab Hatchery project of RGCA
 The Mud Crab Hatchery project of RGCA was initiated to
promote Aquaculture of this species both to augment the
Aquaculture production as well for the natural stock
enhancement of the species in the wild by ranching activities
 This is achieved by the development of a Mud Crab hatchery
facility and development of technology for hatchery seed
production for supply to farmers and Crab fatteners.

13.  A pilot scale hatchery was initially established within the
Seabass hatchery facility during the year 2004
 Presently a full scale Mud Crab Hatchery has been
established with a production capacity of 1 million Crab
instar per annum
 This facility comprises of dedicated sections for broodstock
receiving, quarantine, maintenance, spawning & hatching and
larval rearing
 A separate live feed unit has also been created which ensures
steady supply of quality live feed to the larvae.
 Besides these, supporting systems such as Seawater intake
systems, Filtration and Aeration systems, Reservoirs (200
Metric ton), Effluent treatment and drainage systems as well
as backup power systems have also been provided at the
facility.

15.  Technology Development and Transfer
 Technology for breeding and seed production of Mud crab
has been standardized.
 Protocols for selection of broodstock, broodstock
quarantining, spawning & hatching, larval rearing, live feed
production and use of green water technology have been
developed.
 Technology for Captive maturation of Mud Crab with and
without eyestalk ablation has been developed
 Standardized technology for year round production of Crab
Instar.
 Achieved a record survival rate of 18.1 % in Crab instar
production against the world average of 3.5%. Consistent
survival rates around 7.5% are obtained in RGCA hatchery
operations.
 A package of practice for hatchery seed production of Mud
Crab has been developed.

16.  Present Status
 Remarkable survival rates, as high as 18.1% and an annual average of
8% survival has been achieved at the project against the world average
of 3 – 3.5%, giving scope for commercialization of the technology
 The project has been supplying Crab instars and Crablets (reared at the
RGCA demonstration farm, Karaikal) to farmers and research
institutions since the year 2006
 A record production of 4.27 lakhs Crab Instar has been achieved at the
Pilot Scale facility during the year 2011-12
 Pond-grown females of the mud crabs are obtained from crab
dealers.
 examined for ovarian maturity
 Mature ovaries are dark orange
 Held in a concrete tank with sand substrate and PVC pipes
 mussels, squid and fish at 10-15% of body weight daily and a
SEAFDEC-formulated diet2 at 2%
 Live marine annelids are offered to crabs once every 1-2 weeks as a
supplement
 water depth
 about 30 cm

17.  seawater used for the crab breeders and larvae is pre-
treated in a reservoir with 10-20 ppm calcium
hypochlorite and then neutralized with sodium
thiosulfate after 12-24 h. The water in the tank is
changed daily before feeding
 Eggs released by the female become attached to the
pleopod hairs of the Abdominal flap. Sampling for egg
carrying or berried females is done when water levels are
educed during the water change
 Berried females are then transferred individually to 300-
liter or 500-liter tank with aerated sea water at 32 ppt.
Berried crabs sometimes lose some or all of their eggs
due to fungal infection, failed fertilization, nutritional
deficiency, or environmental stress

18.  At longer incubation periods, the eggs may become
infected with fungus and filamentous bacteria and
infested with protozoan. These infections retard
embryonic development and increase the egg mortality
due to restricted oxygen exchange across the egg
membrane
 To counteract fungal and ciliate infections we treat
berried females with, 0.1 ppm Treflan (44% trifuralin)
every three days in the hatching tank. This treatment has
no adverse effect on the eggs and newly hatched zoeae
 Each spawning produces 0.8-4 million zoeae in 350-525
g S. serrata, 0.7-3 million zoeae in 240-300 g S.
tranquebarica, and 0.4-2.7 million zoeae in 360-465 g S.
olivacea. Hatching occurs 7-14 days after spawning at
temperatures of 26.5-31°C.

19. BROODSTOCK MANAGEMENT
 Gravid females could be produced from the culture site itself. When matured
male and female are stocked together in a pond with salinity around 33 ppt,
females invariably spawn and become ovigerous or berried. Supply of fresh
bivalve meat promotes faster development of gonads.
 Mature crabs and berried crabs are available from commercial catches mostly
during March-May and September-October. Such broods should be necessarily
maintained in salinity around 33 ppt since brackish water is not conducive for
larval production. Spawner crabs are easily transported and they can remain out
of sea water for about 10-15 hours in wet conditions.
 Spawners collected from wild and maintained in hatchery spawn more than
twice in a peried of 4-5 months without undergoing any copulatory ecdysis or
further mating with rnale. This kind of multiple spawning within single mature
instar is an interesting feature of portunid crabs.
 Depending upon the stage of maturation and development of eggs for
fertilization, eye-stalk ablation triggers the mechanism to obtain spawner crab.
 Broodstock thus obtained is to be maintained carefully in separate tanks.
Maintenance of uniform salinity around 33 ppt, daily exchange of water or
provisions for continuous flow system, supply of bivalve meat as feed and
maintenance of water temperature around 28-31° C are essential in broodstock
management.

20. REFERENCE
 http://en.wikipedia.org/wiki/Scylla_serrata
 http://www.roysfarm.com/mud-crab-farming/
 http://rgca.org.in/mudcrab.php
 Quinitio, E. T., Estepa, F. D. P., Rodriguez, E. Seed
production of mud crab Scylla spp. July-September 2002
(volume VII No 3 ) 29
 Marichamy, R. and Rajapackiam. Mud crab hatchery
and fattening. Central Marine Fisheries Research
Institute.