2. INTRODUCTION
• Crab -secondary crop.
• Mono culture system or in poly culture system along with
milk fish /tiger prawn in countries like Thailand, Philippines,
china ,Indonesia, Malaysia, Taiwan, Srilanka and India.
• Alternate candidate species - Rotation of crops.
3. TAXONOMIC CLASSIFICATION
Kingdom : Animalia
Phylum : Arthropoda
Subphylum : Crustacea
Class : Malacostraca
Order : Decapoda
Infraorder : Brachyura
Family : Portunidae
Genus : Scylla
Species : Serrata
Red Mud crab
(Scylla serrata )
Green Mud crab
(Scylla tranquebarica)
5. DISTIBUTION
• Portunus pelagicus and Portunus sanguinolentus- (entirely
marine)
• Scylla tranquebarica, Scylla serrata
-Also called Mud crabs.
-Juveniles - ocean to brackish water.
-Adults -brackish water to ocean.
• Distributed -open waters, intertidal and subtidal regions of
mangrove, estuaries and creeks.
6. • There are over 4,500-odd species of crab which are superbly
adapted for a multitude of habitats.
• They live in tropical and sub-tropical lands and in every sea in
the world except the Antarctica.
• If a crab loses its claws it will die slowly of starvation, but if it
loses one then, remarkably, it’ll grow another.
7. SOFT SHELL CRAB ??
Soft shell crab –crab which have recently
moulted their old exoskeleton and are still soft
8. • The soft-shell season is traditionally marked with the first full
moon in May.
• At that time, the blue crab begins its molting season to
accommodate its summer growth.
• The actual shedding of the shell can take anywhere from one
to three hours, after which it must be removed or the hardening
process will continue, reducing the quality of the soft-shell
crab.
9. • The best soft shell crabs are the blue crabs from the eastern
seaboard of the US and Canada
• Female crabs tend to have more meat than males
11. Why soft shelled crab?
• Can be eaten completely.
• Soft shell meat equal to bone less chicken.
• It has >30% meat low-fat source of high quality protein and
very low in saturated fat.
• contain fewer calories weight for weight than other sources of
animal protein.
12.
13. Season of Peak Breeding Activity and Peak Juvenile Abundance
in India
Region Peak breeding season Peak juvinile abundance
Kerala coast Sep-Feb May - Oct
Tamil Nadu coast Sep - April Dec-May
Andhra Pradesh coast Oct- Feb Dec - Apr
Orissa coast Nov – Jan Mar - jun
West Bengal coast May - Aug Nov - Feb
14. HARVESTING DEVICES
Hard crabs are harvested by several methods:
• Fisherman harvested Crabs may be Hand-collected, Dip
netted, or dredged from habitats favoured by pre-molt crabs.
15. • Peeler or jimmy traps use the hormonal draw of mature
males (“jimmys”) to lure near-mature, pre-molt females into
modified, traditional crab pots.
• Crab “pounds” use flexible wire or netting to guide pre-molt
crabs into entrapments as they seek a reclusive shoreline
refuge for molting.
16. • Ordinary crab pots collect all stages of crabs that are still
feeding.
• The percentage of late pre-molt crabs caught with this method
is thus smaller than with the methods described above.
Currently, most peelers are obtained with crab pots.
17. • Trawl capture uses crabs from the incidental bycatch during
shrimping season.
• It has limitations because of the harvest trauma it causes.
• Bycatch often contains a lower percentage of late pre-molt
crabs.
18. SOFTSHELL CRAB FARMING
• The countries producing softshell crabs are Thailand, Myanmar,
Vietnam, Malaysia and Indonesia. Immature wild
sourced Scylla spp.
• Crabs (60130 g BW) in the intermoult stage are held either in
i.Communal or
ii Individual rearing systems
19. COMMUNAL REARING
• In communal rearing, crabs are held in tanks, bamboo
enclosures or polyethylene nets set in ponds.
• The chelipeds are removed to avoid cannibalism
when the crabs moult.
• Removal of chelipeds may also induce the moulting of the
crabs
20. INDIVIDUAL REARING
• The most common system is individual rearing, in which intact crabs are
heldin perforated plastic boxes with base measurement of 215 x 155 x 90 c
m and detachable covers of 215 x 155 x 25 cm.
• Several boxes are positioned in pontoons or floating platforms. One pontoon
may have 27 sections that can hold 648 boxes.
• The total requirement of 1500020000 crabs needed for such a rearing
system may be completed within 1-
3 weeks depending on the availability of crabs.
21. • Furthermore, stocking is carried out regular to replace dead crabs & those
that have moulted and been transferred for processing.
• To maximize the utilisation of the space in the pond ,herbivorous or
omnivorous fish are also stocked
• Soft shell crabs are fed with fish other cheap protein source @ 8% of
biomass .
• Replacement of 50-80 percent of the total water volume is carried out for
2 to 3 days every spring tide. .
22. • Fresh soft shell crabs are sold to local restaurants and
frozen crabs are exported to Singapore, china.
25. CURRENT STATUS
• It has been estimated that the potential resources of crabs
particularly from the 7,770 km2 of estuaries.
• Backwaters is 13,209 tonnes out of the total potential
resources of 43,816 tonnes from Indian coastal waters.
• The southern part of the coast is potentially richer than the
northern part.
26. • Estimated brackish water area in India is about 1,190,900 ha,
out of which 167,193 ha developed for shrimp farming may
become suitable for crab farming as evidently seen in
Tuticorin, Tamil Nadu.
• Estimated mud crab culture area in Andhra Pradesh is more
than 2,833 ha covering nearly 50 villages
27. • Soft shell crab export from India was 3,054 mt.(2017)
• 2016 - 2,963 mt
• Apart from shrimp culture, mud crab farming, fattening and
soft-shell crab production are now emerging as feasible
business ventures in India.
28. • Floating systems
• On board shedding trays
• Land-based water systems
Culture systems
29. • Traditional method
• Stationary boxes (“cars” or “floats)-made of wood or
fiberglass.
• Attached to a fixed point in open water- i.e bays, inlets or tidal
streams
• Depends on water conditions, water flow.
Floating systems
30. Advantage:
low start up cost
Limitation:
water quality, weather conditions, and site
accessibility.
31. 100 – 200 g used
Basket – 25x25x15 cm
Fixed partially submerged to floating PVC rafts
Rafts arranged in brackish
water ponds.
Each raft 1000 baskets
35-40 rafts in each pond
1 crab in each basket
35000 to 40000 crabs in
each one hectare pond
Soft shell crab Culture in Brackish water
ponds
32. • Once a day with trash fish (chopped into pieces 2.5cm)
• Culture pond – outlet and inlet
• Salinity 10-25 ppt.
• Water depth 1.25-1.5 m
• Temperature 28-30◦C
• DO > 4 mg/L
• Ammonia < 0.1 mg/L
• pH 6.8 – 7.5
• Water exchange depending on water quality
• Usually once in 10 days
Feeding and pond management
33. Harvesting
• Hard shelled crab takes 7-45 days to moult
• 10-30% crabs moult each day
• Baskets checked every 3 – 4 hours
• Soft crabs immediately removed for
processing – shells harden in 3-4 hours.
34. • On board shedding trays are found on the
decks of shrimp vessels.
• Peelers harvested in by-catch are placed in
them and supplied with natural water pulled on
board.
• Deck space is at a premium, but the captive
labour force of the crew makes sorting and
retrieving soft crabs an integral part of routine
duties.
On board shedding trays
36. • Soft crab operations using open loop water are
similar to floating systems, as they often use
the variable but inexpensive water of an
adjacent water body.
• Start-up and operation are economically
attractive to many producers who have
waterfront access and live within a reasonable
distance of the shedding system.
Land-based open loop water systems
37. • Trays are a standard design, and are often used
in multiples of four for each stage.
• Electricity for the pump(s) and material costs
for the all-weather covering add to the costs.
38. • Closed loop or recirculating systems are different
from other system designs because they hold and
reuse water, which circulates through the series of
trays before being purified and used again.
• The initial source of this water can be suitable surface
water from adjacent waterways, well water, or
municipal water systems (after appropriate water
treatment).
Land-based closed loop water systems
39. • Closed loop systems have the advantage of being
completely self-contained without exposure to the
highly variable water quality conditions of many
estuarine water bodies.
• The most appealing attribute of the closed loop
system is the ability to locate the shedding
operation away from any surface water.
• Water quality can also be managed more easily
than in other setups. Land cost and proximity to
the operator’s home are often strong factors in
deciding to use this type of system.
40. • Moulted crabs are inspected every 4 hours through th
e holes of each box by pulling the string to move the
pontoons.
• Newly moulted crabs are retrieved immediately after
moulting and held in freshwater for 30-60
minutes prior to processing.
• Softshell crabs can be eaten whole when cooked with
out removing the shell and claws.
Harvesting techniques
41. Market and trade
• For soft-
shell crabs, the price depends on the size and condition of the cra
bs.
• The highest priced are those that are >200 g.
• The lowest priced are crabs which lack chelipeds, regardless of
their size and those with slightly hardened shells.
• Softshell crabs are marketed locally or exported to Hong Kong, S
ingapore, Republic of Korea ,Japan, Taiwan , European
the United States of America and Pacific Islands Trust Territories.
• The cost ranges from USD 7 -10.0/kg (5-15 count).
42. • Lack of seed stock for the expanding industry.
• Cost effectiveness in seed production.
• Prevention of diseases in both hatchery (bacter
ial and fungal infections, and protozoan infesta
tion) and grow out (WSSV).
• Cannibalism
Main issues
