Crab Culture Training in India/Crab Cultural Practices
Let us talk about crab farming training in India and cultural practices of mud crab/freshwater crab.
Among the marine edible crustaceans, crabs occupy the third position by virtue of their delicacy, demand, and price. the first two being shrimps and lobsters. Among the 990 species of marine crabs, 34 species are growing to a larger size and hence they fetch a higher price. Aquatic breed, crabs belonged to the family Portunidae and they can be recognized by the presence of flattened last pair of legs, which help them in swimming in the columnar Haters. Species belonging to genera Scylla, Portunus, and Chaq-bdis which grow.to 0.2 to 2.3 kg are considered as commercially important portunid crabs as they are utilized for both local consumption and export trade.
Mud crabs as commercially important crabs, Mud crabs stand first in the context of both capture and culture fisheries due to their larger size, great demand, and higher price. A total of 3,500 tones (2,500 tones from brackish water and 1000 tones from the marine region) of mud crabs are caught annually from India. At the bottom of the article, you can find crab training in India information./
Distribution and habitat:
Both the species of mud crabs are found in the shallow coastal waters, lagoons, estuaries, backwaters, brackish water lakes, mangroves, and inter-tidal swamps of east and west coasts of the mainland and the creeks and bays of Andaman and Nicobar Islands. They prefer sandy or muddy slush bottom. Both the species remain buried under the substratum during the day and are active at the night. While the large? species (S. tranquebarica) remains buried under the substratum, the smaller species (S. serrata) usually makes burrows at the bottom and in the embankments of brackish water canals and fish farms. Both the species migrate into brackish water areas during their post-larval stage (megalopa stage), Early juveniles abound the intertidal region, while the adults occupy the deeper portions of tire estuaries. After attaining maturity, adults migrate, especially the berried females to tire sea for breeding.
Males and females can be identified in juveniles measuring above 35 mm in carapace width (CW) by the shape of the abdominal flap. In the male, the abdominal flap is slender and triangular (Plate 1 D), while it is broad and triangular in immatured (Plate 1 E) and semi-circular in matured and berried females (Plate 1 F). In both sexes, the abdominal flap in live crabs, 7s-folded firmly against the ventral side of the body.
Food and feeding:
Both tile species of mud crabs are carnivorous. They feed on slow-moving and bottom-dwelling animals such as bivalve molluscs, small crabs, and dead and decayed animal materials. These crabs are also called scavengers. In fact, they cannot catch alive and moving prey.
The growth in mud crabs is manifested with the shedding of the outer shell. Before moulting, a new exoskeleton shell is formed below the old, hard and dead shell. During the moulting process, the old shell is cast off. The formation of a new shell and casting off an old shell is called as moulting process, which requires energy. The increase in the size of the crab after moulting takes place due to the absorption of water by the tissues of the body and thus the moulted crabs are larger in size. Since (lie moulted crabs have utilized stored energy for moulting, they weigh less and they contain more water. The newly moulted crabs with watery meat and soft exoskeleton are called “water crabs”. Such “water crabs” remain defenseless and become easy prey to other animals, particularly other hard mud crabs. The newly formed shell of the moulted crabs gets hardened after 3-4 days. after moulting. The frequency of moulting is more in juveniles and sub-adults, while it is less in adults. The hard-shelled crabs are called “meat crabs”, which fetch a higher price.
In the experimental field culture, the early juvenile crabs (15 to 60 mm in CW/3 to 20 g in total weight) grow at a rate of 7 to 12 mm / 3 to 13 g per month, while juvenile crabs (61 to 80 mm / 25 to 70 g) exhibit a monthly growth of 11 to 12 mm / 45 to 97 g. In the sub-adult and adult stages, the monthly growth works out to 8 to 10 mm / 100 to 130 g. The larger species (S. tranquebarica) attains a maximum size of 220 nun / 2.5 kg and the smaller species (S. serrata) 140 nun / 0.5 kg in the wild.
Attainment of maturity in females can be easily noticed by the change in the shape of the abdominal flap, from triangular to half-round/horseshoe-shaped (Plate 1 E & F). For males, there is no external character to identify the matured ones. The size at maturity for the female is about 120 mm for larger species (S. tranquebarica) and 83 nun for smaller species (S. serrata). After the onset of maturity, the development of ovary takes place internally. Initially, the color of the ovary is bright orange which changes to deep yellow before the extrusion of eggs. The inner ovarian development can be determined by pressing down between the carapace and abdominal flap. The eggs, if matured, are visible by their yellow color.
The copulation takes place between a hard male and a freshly moulted soft female. Prior to copulation, a hard-male climb over the back of a hard female crab, clasping her by Ms chelipeds and the first two pairs of walking legs. This formation is called “doubler’ or “premating embrace”, which lasts for 2-3 days. The pair separates when the female reaches the verge of moulting. The female moults and it is called as “pre-copulatory moult”. The male assists the female during the pre-copulatory moulting. A few hours after moulting, the male embraces the soft female again for the actual mating. The male gently turns the female over on her back using Ms chelipeds, while the female unfolds her abdominal flap and holds the male in position. The copulation lasts for 6-8 hours. During the tire copulation act, the male deposits spermatophores in the tire seminal receptacles of the female.
When the eggs become ripe, they are fertilized by the stored spermatophores. Later, they are extruded and remain as “mass” or “sponge” and attached to the hair-like branches of four pairs of appendages of the abdominal flap.
Cultural Practices of Crabs
Types of culture Two types of culture operations are practiced:
- Grow-out culture in earthen ponds provided with proper fencing, where juvenile crabs can be raised to marketable size over a period of 3-4 months.
- Fattening process in which “water crabs” can be reared in earthen ponds with fencing, pens, and cages for a period of 3 to 4 weeks to gain weight or for the full development of ovary in female crabs.
Grow-out culture operation
Suitable site Ponds can be constructed in tide-fed estuaries, backwaters, and creeks. The crab ponds are established in traditional fish/shrimp farms, by converting one portion adjoining the brackish water canal, which would help increase the overall income of traditional fish/shrimp farmers.
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Earthen ponds of 0.1 to 0.4 line in size and rectangular in shape having a sandy or muddy or clay loamy bottom soil are constructed with minimal digging, which provides ample soil for bund construction. The wider axis of the pond may face the backwater canal in order to live a greater tidal effect through a traditional wooden sluice.
Before stocking, the ponds are prepared by removing unwanted organisms by netting. To prevent the escape of stocked crabs from the pond, fencing with suitable materials such as casuarina poles, bamboo split matting, G.I.chicken wire mesh, nylon netting, and asbestos sheet to a height of 1 m is erected either in the thinner edge of the pond or on the top of the earthen bund. The fencing may be positioned at a 45-degree angle towards the inner side of the pond, which will prevent the climbing and escape of small crabs. Since mud crabs are highly cannibalistic, earthen and PVC pipes and worn-out tires may be placed as hide-outs/shelters to reduce the fighting among the normal hard crabs and mortality of the soft “water crabs”. A row of earthen mounds may be constructed in such a way that they remain submerged during the high tide and exposed during the low tide, in order to serve as natural habitat.
The harvest of crabs can be effectively done in tide-fed ponds by letting in water through the sluice into the pond during the incoming tide (high tide). As the water flushes in, mud crabs tend to swim against the incoming water and congregate near the sluice gate and they can be caught with the help of a scoop net. The crabs are partially harvested by baited lift nets and bamboo cages/traps (Plate 3 C & D). Complete harvest is done by scoop nets at the sluice gate and also by hand picking at the lowest low tide levels. The expected survival rate would be around 70 to 80 %. The “water crabs” encountered in the final harvest are utilized for fattening purposes.
The pair of largest legs with pincers (chelate legs) of each live crab should be firmly tied up with the body by jute/nylon thread to curb their movement and to avoid fighting among them. The method of packing the live mud crab is as follows: A wooden stick is placed on the body of the crab for the instant arrest of its movement and a jute/nylon thread is placed in between the frontal portion of the body and chelipeds. After keeping the cheiipeds in folding posture, the thread is coiled around their fingers and both the ends of the thread is put into a double knot at the rear end of the crab, as shown in Plate 4 A to E. Wet seaweeds are kept in between the packed layers of crabs to enhance their moist and cool conditions during the transport from place to place for local consumption. The tied-up crabs are washed with fresh seawater and packed either in a bamboo basket or in the perforated thermocole box for export purposes (Plate 4 E & F).
Mud crabs are generally sold in live conditions for both local consumption and live crab export trade. For the marketing purpose, mud crabs should be graded as the “extra-large” (1 kg and above), “large” (500 g to 1 kg), “medium” (300 to 500 g), and “small” (200-300 g). The matured and berried female crabs have a higher price. The meaty crabs weighing above 300 g are considered for five mud crab export, while tire under-sized crabs (less than 300 g) and the crabs which have lost their limbs are sold by number in local markets. They are marketed only in live condition, as there is an aversion among the consumers for dead mud crabs.
The mud crabs and other portunid crabs are processed and exported in the form of frozen and canned crab meat from 1962. Since the export trade for live mud crabs has started in 1987-88, the demand for the same is ever increasing. The quantity of frozen and canned crab meat and live mud crabs exported.
Crab Training in India/Crab Cultivation Training Centers in India:
Rajiv Gandhi Center for Aquaculture:
Rajiv Gandhi Center for Aquaculture is providing Mud Crab Aquaculture. raining programs in Recirculation Aquaculture Systems, as well as Live feed production systems, have also been organized at the TTTAC. RGCA also brings in International experts from various spheres of Aquaculture to impart training in highly relevant aspects related to current aquaculture activities in the country from time to time. TTTAC organized an International workshop cum Training program on Shrimp pathology.
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Central Institute of Brackishwater Aquaculture:
Central Institute of Brackishwater Aquaculture under the Indian Council of Agricultural Research (ICAR) was established in 1987.
The research and development programs in brackishwater aquaculture are carried out under the framework of the following five divisions:
- Crustacean Culture Division (CCD)
- Fish Culture Division (FCD)
- Nutrition, Genetics & Biotechnology Division (NGBD)
- Aquatic Animal Health & Environment Division (AAHED)
- Social Sciences Division (SSD).
CIBA offering courses on Crab Farming Techniques, Management, and scientific practices for crab culture and Crab Feeding Technology. For crab training in India address, find the below one.
Course Fee: Course is 5000 to 10000 Rs.
Course Duration: 1 week to 10 days.
75, Santhome High Road, Raja Annamalai Puram,
Chennai – 600028 Tamil Nadu,
Phone: 044-24610565; 24616948,
E-mail: firstname.lastname@example.org, email@example.com
Central Marine Fisheries Research Institute:
The Central Marine Fisheries Research Institute is by The Government of India on February 3rd, 1947 under the Ministry of Agriculture and Farmers Welfare and later it joined the ICAR family in 1967.
CMFRI offering Training Program on Crab Resources and Culture Methods. The duration of training is 2 days. For crab training in India course find the following address.
Central Marine Fisheries Research Institute
Post Box No. 1603, Ernakulam North
Kochi- Kerala – 682 018.
Phone: +91 484 2394357 /12, 2391407,
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