Presentation on "Culture of Mud Crab" M.F.Sc (Master of Fisheries Science) - 1st Semester

1. Culture of Mud Crab
 Submitted To:-
 Dr. K. H. Vadher
 Associate Professor
 Department of Aquaculture
 College of Fisheries,
 Veraval
 Submitted By:-
 Hodar Ashish R.
 M.F.Sc (1st Semester)
 Roll No:- 5
 Regs. No:- 2030319005

2. Content
Sr. No Topic
1 Introduction
2 Scientific Classification of Mud Crab
3 Biology of Mud Crab
4 Hatchery Technology of Mud Crab
5 Culture of Mud crab
6 Diseases In Mud Crab
7 Conclusion
8 References

3. Introduction
 The edible crabs of commercial importance are Scylla tranquebarica,
Scylla serrata, Neptunus pelagicus and Neptunus sanguinolentus.
 The former two species S. Tranquebarica, S. serrata commonly called as
Mud crabs which migrate to brackishwater water for growth while they are
juvenile and the adults migrate to brackishwater to the ocean for breeding
and spawning.
 While S.tranquebarica are found in open waters whereas S. serrata are
found in burrows in the intertidal and sub-tidal regions of mangrove,
estuaries and creeks.
 It also has world wide distribution, occurring in Africa, Pakistan,
Anadaman, Japan, Australia, New Zealand, Etc.
 In India, crabs formed secondary crop along with shrimp in traditional tide
fed farm of Pokkali fields of Kerala, Bheris of West bengal and Khazan
lands of Karnataka.
 In recent years, mud crabs production through culture has been practiced in
brakishwater pons either in a monoculture or polyculture system along with
milkfish/tiger prawn in countries like Thailand, Philippines, China,
Indonesia, Malaysia, Taiwan, Sri-lanka and India.

4.  It can be considered as an alternative candidate species for rotation of crops
in brakishwater ponds, particularly in areas where shrimp farming has
collapsed due to white spot disease.
 In the fishery, it take two years to reach into the commercial size (300-800
g depending on species), but in aquaculture this can be reduced within one
year (Trino et al., 1999; Christensen et al., 2004; Ut et al., 2007b).
 The crabs are “farmed” in variety of ways. Firstly, soft empty post-molt
crabs are harvested from the fishery individually and then fed with trash
fish to “Fatten” them for market.

5. Scientific Classification of Mud Crabs
Kingdom :- Animalia
Phylum:- Arthropoda
Subphylum:- Crustacea
Class:- Malacostraca
Order:- Decapoda
Infraorder:- Brachyura
Family:- Portunidae
Genus:- Scylla
Species:- S. serrata

6. Biology of Mud Crab
1. Size at first sexual maturity:
 Scylla Tranquebarica:- 120 mm (carapace width)
 Scylla serrata:- 83 mm (carapace width)
2. Sexual dimorphism:
Male Female
Abdominal flap is slender and triangular. Abdominal flap is broad & triangular in
immature female and it is semi-circular
in mature female (berried female).
Claws are larger Claws are smaller
Appendages are present on first and
second abdominal segments
Appendages are present on second to
fifth abdominal segments
Female (mature) Male

7. 3. Breeding season:
4. Mating:
 Firstly, pre-mating embrace takes place between a hard-shelled male and
female for 2-3 days. After then female start moulting which is refers as “Pre-
copulatory moulting”. It is mainly done to cast-off her old shell.
Region Peak Breeding Season
Kerala coast September – February
Tamil nadu coast September – April
Andhra Pradesh coast October – February
Orissa Coast November – January
West Bengal coast May – August

8.  After pre-copulatory moulting, actual copulaion starts.
 The male turns the soft bodied female upside down by using his chelipeds,
female unfolds the abdomen. This lasts for 6-8 hours at which male
deposits the speratophores in the seminal receptacle of female.

9. Hatchery Technology of Mud Crab
1. Brood Stock Rearing:
 Young crabs of 80-100 gm are stocked @2-5 numbers per square meters.
 Ponds can be constructed in coastal areas with facilities for water
exchange by tidal effect.
 Feeding can be done with trash fish at a rate of 5% of body weight which
is increased in later rearing period of 4 months.
 Water level should be maintained at 60 cm, otherwise brood crab climb
out.
 For gonadal maturation, eyestalk ablation of females can also be done.
Within 15 days from the time of eyestalk ablation, berried females are
ready for hatchery use.
2. Hatchery:
 The berried female are released into 500 litre capacity FRP /cement tanks.
 The zoea larvae hatched out and incubation period is 8-15 days.
 Each zoea stage is of 3-4 days duration, at the end of which they moult
into next stage. After 5th moult (zoea I, zoea II, zoea III, zoea IV, zoea V),
the larvae becomes megalopa.

10.  Megalopa grows to juvenile crabs within 8-11 days.
 From zoea I to zoea V heavy mortality is observed, from zoea V to megalopa less
mortlity is observed and from megalopa to crab I stage, cannibalism is serious.
3. Feeding the larvae:
 Rotifer and Artemia nauplii have been shown to be the suitable feed for larvae.
 Rotifer are preferred during early stages whereas artemia nauplii are given for
megalopa to crab stage.

11. Culture of Mud Crab
 Most of the crab farmers depend on the wild caught juveniles for the seed
stock.
 In Philippines, the juveniles of 2 cm carapace are collected by means of
bamboo traps, lift nets or scissor nets.
 They stocked seed in milkfish ponds at a low rate of 500-1000 per hectare
and repeated stocking and harvesting are practiced.
 In pond, they feed on natural food such as algae, crustaceans and other
animals.
 Some farmers feed them with trash fish or other available animal products
@ 5-7% of their body weight.
 Juvenile grow marketable size within 6 months with the carapace width of
11-14 cm.

12. 1. Culture methods:
i. Monoculture:
 In culture system, hiding places should be provided. Mangrove plants like
Avecenia Sp., Rhizopora Sp., are allowed to grow in the ponds for
offering hiding places.
 For monoculture, specially designed tidal ponds with a sandy bottom and
a supply of salt water of 15-30 ppt salinity are used.
 Ponds with dikes of about 1m height, to prevent juveniles are stocked at a
time.
 They feed on soft-shelled snails, trash fish, fish offal and other animal
matter.
 The maximum size attained by a male crab is about 2 Kg.
ii. Polyculture:
 For polyculture of crabs in brakishwater ponds, serrated crabs grows
along with milkfish, shrimp or seaweeds.
 For growing them larger ponds (0.5-2.0 ha) are used.
 The oblique fences of bamboo or plastic have to be erected on the dikes
to prevent escape of crabs.

13.  Male and female juveniles (1.5-3 cm carapace width) are stocked
@1000/ha and fed the same food as in monoculture.
 Adequate feeding is reported to reduce the cannibalism.
 The crabs attains marketable size within 6 months with a survival rate of
50-70%, depending on the size of juveniles stocked.
 The production recorded under polyculture in India is 690 kg/ha/yr.
2. Harvesting:
 Harvesting can be done with dip nets baited with trash fish.
 The most efficient mean of harvesting is by making the use of their habit
of congregating in the central tank when water is let in.
 It is easy to catch them from the tank with dip nets.
3. Transportation:
 For transportation to market, each individual live crab is bound with a
wetted heavy straw rope to facilitate handlings and also to keep the animal
moist.

14. 4. Crab Fattening:
 Fattening is primarily a value adding process. For example, low-value,
“ban” market sized mud crab may be taken and fed for a short period to
harden the shell and restore the flesh content (Dat, 1999).
 This involves holding of large-sized crabs (recently molted) until they
become hard.
 Crabs are fed with bivalve meat or trash fish. Feeding is done daily at the
rate of 5 to 10% of body weight.
 The duration of fattening is 20 days.
 This type of activities has become very popular throughout Asian
countries due to increasing demand for producing large size hard shelled
mud crabs.

15. Diseases in Mud Crab
1. White spot diseases:
 Cause:- WSSV is caused by rod-shaped DNA virus belonging to genus
Whispovirus.
 Effect on crabs:- mortality of crabs due to the WSSV.
 Prevention and control:- install screens and fences to ensure biosecurity of
culture, disinfect spawners and provide natural food.
2. Bacterial shell diseases:
 Cause:- sucrose-fermenting or non-sucrose fermenting vibrios species which
are chitin-digesting bacteria.
 Effect on crabs:- mortality and extensive shell erosion.
 Prevention:- provide optimum amount of sandy substratum which reduce
build-up of fouling organisms on crabs.

16. 3. Shell Discoloration:-
 Cause:- low soil pH, acidic soil and formation of iron precipitates on crab
shells.
 Effect on crabs:- effect the organs like gills and eyes, growth retardation and
death.
 Prevention and control:- use lime to correct pH and prepare pond properly to
avoid acid sulfate problems.
4. Incomplete molting:-
 Cause:- low temperature and nutritional causes.
 Effect on crabs:- abnormal movements or swimming behavior and affected
crabs become easy prey to healthy individuals.
 Prevention and control:- grow crab at optimum temperature and provide
adequate diet for successful molting.

17. 5. Blackened Ovaries:-
 Cause:- deposition of pigments melanin as a result of mechanical or
microbial injury and also due to lack of vitamin C in diets.
 Effect on crabs:- spawning failure, affect fecundity in females.
 Prevention and control:- provide adequate diets with available vitamin C
sources in the diets.

18. Conclusion
 Mud crabs farming is becoming very popular because of its good demand
and better price in the international markets.
 Mud crab can be grow in monoculture or in polyculture with milkfish or
the seaweed; which provide advantages in culture systems.
 It can be considered as an alternative candidate species for rotation of
crops, particularly in areas where shrimp farming collapsed due to white
spot diseases.
 The fattening of mud crabs provide employment opportunities for the
fisher folk as a means of alternative livelihood.

19. References
 Trino, A. T., Millamena, O. M. & Keenan, C. (1999). Commercial evaluation of
monosex pond culture of mud crab. Scylla species at three stocking densities in
the philippines. Aquaculture, 174, 1-2.
 Christensen, S. M., Macintosh, D.J. & Phuong, N. T. (2004). Pond production
of the mud crabs Scylla paramamosain (Estampador) and S. olivacea (Herbst)
in the Mekong Delta, Vietnam, using two different supplementary diets.
Aquaculture research, 35, 1013-1024.
 Ut, V. N. , Le Vay, L., Nghia, T. T. and Walton, M. (2007b). Comparative
performance of hatchery reared and wild Scylla paramamosian (Estampador,
1949) in pond culture. Aquaculture reasearch, 38, 1593-1599.
 Dr. P. C. Thomas. (2014). Breeding and Seed production of Fin fish and Shell
fish. Pg 250-256.
 Dr. V. Sundararaj; Dr. B. Srikrishnadhas. (2000). Cultivable Aquactic
Organisms. Pg. 60-61.
 Dr. M. Gaidhane; D. N. Saksena; H. Singh; M. Subhas. (2016). Aquaculture. Pg
290-294.

20.  Dat, H. D. (1999). Description of mud crabs (Scylla Spp.) culture methods
in Vietnam. In: Mud Crab Aquaculture and Biology (eds C. P. Keenan & A.
Blackshaur), pp. 67-71. proceedings of an international scientific forum
held in Darwin, Australia, 21-24 April, 1997. Australian Centre for
International Agricultural Research.
 Brian D. Paterson and David L. Mann. (2011). Mud Crab Aquaculture.
Recent Advances and New Species in Aquaculture. Pg. 115-135.
 Scylla serrata. Wikipedia.en.wikipedia.org/wifi/scylla-serrata.