Mud crabs, also known as mangrove crabs, occur widely in estuaries and along tropical, subtropical and warm temperate coasts in the world. There are four species of mud crab (Family: Portunidae), Scylla serrata, S. tranquebarica, S. paramamosain and S. olivacea that are the focus of both commercial fisheries and aquaculture production throughout their distribution. They are among the most valuable crab species in the world, with the bulk of their commercial production sent live to market.

1. M
ud crabs, also known as
mangrove crabs, occur
widely in estuaries and
along tropical, subtropical
and warm temperate
coasts in the world.
There are four species
of mud crab (Family:
Portunidae), Scylla serrata,
S. tranquebarica, S. paramamosain and S. olivacea that are the
focus of both commercial fisheries and aquaculture production
throughout their distribution. They are among the most valuable
crab species in the world, with the bulk of their commercial
production sent live to market.
Mud crab constitutes an important secondary crop in the
traditional prawn or fish culture systems in some of the coastal
states & Union Territories and has become increasingly popular
by virtue of its meat quality and large size.
In India, the mud crabs have come into prominence in the early
eighties with the commencement of live crab export to the South
East Asian countries which has created a renewed interest in the
exploitation as well as in the production of mud crabs through
aquaculture see Table 1.
Among six, two species of mud crabs, namely Scylla serrate
and Scylla tranquebarica are found in the inshore seas, estuaries,
backwaters, coastal lakes and mangrove swamps of all maritime
states on the main land and the creeks and bays of Andaman and
Nicobar Islands. Both the species co-exist in the inshore sea as well
as in the inland brackish waters preferring muddy or sandy bottom.
The immense market demand for mud crab
Scylla serrata, commonly known as the mud crab or green crab,
has an immense market demand all over the world, particularly in
MUDCRAB
FARMING
ININDIA
by Dr B Laxmappa, Fisheries Development
Officer, Telangana, India
22 | May | June 2016 - International Aquafeed
FEATURE

2. South East Asian countries. This seafood delicacy is considered
as one of the tastiest of all crab species. This is often sold in live,
in many international markets. India earns foreign exchange to
the tune of 18 million US $ by exporting live mud crab captured
from the low-lying coastal belts across the country.
Therefore, natural stocks of mud crab in the country are under
constant pressure from fishing.
Culture practices
Among the edible species, Scylla serrata, is
popular because of its size, meat quality, high
price and export potential. The ability of
mud crab to grow fast and its suitability
for culture in brackish water and
estuarine areas make it attractive to
develop mud crab culture/fattening
programmes in India to meet
the increasing demand for
export and domestic market.
A community-based crab
fattening in cages project
was implemented first
time in Tamil Nadu state in
2006 for alternative livelihood
purposes especially for the fisher women.
This has proved to be a great success not
only in terms of generating extra income
to the family through the Self Help Groups
(SHG) but also in creating an awareness
among fisher folk about the value of marine
resources and the need for conservation and
sustainable utilisation.
There are two basic forms land-based mud crab
culture practices - fattening of crabs with low flesh content/
water crabs and grow-out of juveniles to market size. The most
common culture systems for mud crab growout are pond culture
and mangrove culture.
Mud crab farming is traditionally a small-scale, family-run
business in India. Earthen ponds are commonly used in pond
culture. With simple modifications, existing marine shrimp
ponds utilised for mud crab growout in some areas. The size, of
the ponds are generally between 0.3 and 0.5 hectare with a water
depth between 0.8 and 1.5 metres.
Various structures, most often simple net fences, but sometimes
also concrete or lined pond banks, are constructed to prevent
escapes. The more commonly used system is semi-intensive
enclosures, often constructed in intertidal zones using easily
harvested bamboo. The stocking density is generally between one
and five crabs per square meter.
Feeding
Care is taken to provide sufficient food for better growth and
also to avoid cannibalism. Although crabs can utilise natural
diets, supplementary feeds like trash fish, animal offal, cheap
mollusks and sometimes formulated feeds for marine shrimp, are
used to feed mud crabs.
Feeding rates are generally between three and ten percent
of biomass, with a decreasing feeding ratio as they mature.
The culture period for growout from juvenile to market size is
generally five to eight months, and survivals of 30-70 percent are
commonly achieved. The duration of fattening is normally 20
days. Fattening of mud crab is popularly undertaken in the states
of Andhra Pradesh, Tamil Nadu, Kerala, Karnataka, Orissa and
West Bengal.
Harvesting
The crabs are harvested after the shell hardens and before the
next moulting. The harvesting can be effectively done in tide-fed
ponds by letting in water through the sluice into the pond during
high tide. As the water starts flushing in, the mud crabs tend to
swim against the incoming water and congregate near the sluice
gate.
The crabs can be caught with the help of a scoop nets and
also by hand picking at the lowest low tide levels. Harvesting
preferably in the early morning hours or evening.
Marketing
Mud crabs are popular throughout the Indo-Pacific region,
particularly in countries where they occur naturally. They remain
alive out of water for considerable periods of time (more than
1 week when kept moist) after capture and are traditionally
marketed alive. However, they are also sold as a frozen for
the newly emerging soft-shell crab market. Although the price
may vary substantially from country to country, mud crabs are
generally a high-priced seafood item in local markets.
The scope for live mud crabs export has opened up good
opportunities for crab farming/fattening. Export market of
live crab especially to South East Asian countries is picking
up steadily. Kerala is a major supplier to the export trade and
Chennai is the main centre of live mud crab exports to Singapore
and Malaysian markets. Crab is poised to be the next potential
sea food in the world market among the marine crustaceans next
to shrimp and lobsters.
The export as well as domestic market of crab is met through
crab landings from the natural collection / harvest from the sea
as also from the brackish water areas. Frozen crab meat and live
crabs are exported from India to south East Asian countries.
International Aquafeed - May | June 2016 | 23
FEATURE

3. Scylla serrata is much in demand in the domestic market and
fetches a good price, compared to other species of crab. Medium
and large crabs of more than 14cm carapace width and weighing
more than 400g are collected exclusively for export purposes
from West Bengal, Orissa, Andhra Pradesh, Tamil Nadu, Kerala,
Karnataka, Goa, Maharashtra and Gujarat.
The rates vary for live crabs depending on its size. Live mud
crabs of 100grams to 300 grams will earn US$5 to US$7 and
those weighing more than 400 grams earn US$11. In India, live
crabs retail at IMR 300 to 350 in Bangalore and Delhi. During the
peak season from June to September the catch can go up to one to
two tons per day and it dwindles thereafter.
Role of MPEDA & RGCA
Marine Products Export Development Authority (MPEDA),
a nodal agency set up by the Government of India in 1972
for the promotion of seafood exports from India. In order to
strengthen the production base of the mud crab so as to facilitate
a sustainable source of mud crab for export, Rajiv Gandhi Centre
for Aquaculture (RGCA), the research and development arm of
MPEDA, has established a mud crab (Scylla serrata) hatchery in
the state of Tamil Nadu in 2013 that regularly produces juvenile
crablets for its demonstration farm and local farmers.
This hatchery is one among very few mud crab hatcheries in the
world, Philippines, Vietnam and China being the other countries
having them. The hatchery has been regularly been producing
mud crab seed reared to crablet sizes at its demonstration farm
and supplying to farmers in the area. Crablets have also been
supplied to several research institutions like the Central Institute
of Brackish water Aquaculture (CIBA) and National Institute
of Ocean Technology (NIOT) for their farming demonstrations.
The facility has also been carrying out ranching of crablets in
estuarine and mangrove areas in Tamil Nadu from time to time
for natural stock enhancement.
Owing to the highly cannibalistic nature of the larvae of this
species, larval rearing of mud crabs is a very challenging task
and survival rates achieved are extremely low when compared to
other crustacean species and species of finfish. But, the scientists
at RGCA have achieved a breakthrough survival of 7 to 14
percent against the world average survival rates of 3 percent.
This encouraging breakthrough achieved by RGCAcan open up
avenues for commercialisation of mud crab hatchery technology
leading to organised mud crab aquaculture in the coastal areas of the
country especially among the weaker sections of the society giving
them an alternate livelihood option and also strengthens the production
base of mud crab for export in live and value added products. This can
Table 1: Commercially important crab species and its production source in
India.
Common
Name
Scientific
Name
Production
source
Common size
of growth
(Carapace
width)
Green crab
Scylla serrata
(Forskal, 1775)
Capture &
Aquaculture
13-15 cm
Green crab
Scylla tranquebarica
(Fabricius, 1798)
Capture &
Aquaculture
20-22 cm
Red crab
Scylla olivacea
(Herbst, 1796)
Capture 13-15 cm
Spotted crab
Portunus
sanguinolentus
(Herbst, 1783)
Capture 10-12 cm
Blue crab
Portunus pelagicus
(Linnaeus,1766)
Capture 10-15 cm
Cross crab
Charybdis cruciata
(Mc Neill, 1929)
Capture 10-15 cm
24 | May | June 2016 - International Aquafeed
FEATURE

4. also result in reducing the fishing pressure on the natural stocks and
thereby facilitating natural stock enhancement in the mangrove forests.
Identifying live crab exports as a potential money spinner, the
Indian seafood industry is all set to rear mangrove crabs, so as to
scale up the export of the crustacean that commands high price
in the global market, particularly in Southeast Asia. The MPEDA
has begun farming of crabs in the mangroves of Sindhudurg
district in Maharasthra state through coastal fishermen. Green
mangrove crab is a much sought-after variety and fetches a price
of INR 1,000 to Rs 1,400 a kg in the world market.
At present, mud crabs are reared in farms or ponds in states like
Andhra Pradesh and Kerala. The seeds are supplied by the Rajiv
Gandhi Centre for Aquaculture in Tamil Nadu, the R&D wing
of MPEDA, which achieved a breakthrough in crab hatchery
technology with one of the highest survival rates in the world.
The seeds are farmed by the self help groups of local fishermen
and then supplied to the exporters once it reaches full size in
around ten months. Live crab exports, mostly done by air from
Chennai and Mumbai, are at present pegged around INR 220
crore (2,200 million) annually and has grown only marginally
over the past few years.
Once the mangrove rearing becomes widespread, MPEDA
hopes to increase it several times. To ensure steady supply of
seeds, the agency is in the process of setting up another hatchery
in Maharashtra. The crab exports have not picked up in a big way
in Maharashtra and Gujarat. Unlike in Chennai, there aren’t many
exporters in Mumbai who can share the cost of booking and
sending the consignment by air.
Conclusion
Mud crab farming is becoming very popular in the coastal
districts of India; owing to the good demand and better price
of mud crab in the international market. Mud crab has emerged
as a good potential exportable commodity as well as means of
livelihoods of the coastal poor communities in India. Though
mud crab constitutes an important secondary crop in the
traditional prawn or fish culture systems in some of the coastal
states, the state’s coast has yet to fully wake up to its potential.
The fattening of mud crab, which is non-existent there, can
provide employment opportunities for the fisher folk as a means
of alternative livelihood besides promoting crab fishery.
Research institutes and the Central Marine Fisheries Research
Institute (CMFRI) should create awareness among farmers
exploit the potential of crab farming in potential coastal regions
of India. The West Coast is mainly dependent on fish catch, like
Andhra Pradesh is dependent on shrimp farming. Unless there
is a crisis people will not move out of their comfort zone to try
something new.
All references are available on request.
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