Thursday, November 14, 2019 Information Gateway on Agriculture to Convert "Know How To Do How" മലയാളം
Fisheries > Culture Fisheries > Crabs

Harvesting

The crabs are harvested after the shell becomes sufficiently hardened and before next moulting. The harvesting is done by draining the pond and using scoop nets and ring nets with baits. Harvesting should be done in the early morning hours or evening to prevent mortality of crabs due to overheating of water at noon time. In a year 9 to 10 cycles of fattening can be taken from a pond.

The harvesting of crabs can be effectively done in tide-fed ponds by letting in water through the sluice into the pond during high tide. As the water flushes in, the mud crabs tend to swim against the incoming water and congregate near the sluice gate. They can be caught with the help of a scoop net and also by hand picking at the lowest low tide levels. The expected survival rate would be 70 to 80%. The "water crabs" encountered in the final harvest can be utilised for "fattening" purpose.

Packing

The first pair of largest legs with pincers (chelate legs) of each crab should be firmly tied up to the body by jute/nylon thread to avoid fighting among them. The method of tying a live crab is as follows: a stick is firmly placed on the carapace for instant arrest of its movement and the thread is placed in between the frontal portion of the body and chelate legs. After keeping the chelate legs in folding posture, the thread is coiled around their fingers (chelae) and both the ends of thread are put into a double knot at the posterior end of the crab. Wet seaweeds are kept in between the packed layers of crabs to enhance moist and cool condition during transport from place to place. The tied-up crabs are washed with fresh seawater and packed either in bamboo baskets or in perforated thermocole boxes for export purposes.

mudcrabs

Tied crabs

packed

Packed crabs

Economics

Economics of three systems of mud crab farming

Culture Method

Monoculture

Polyculture

Fattening

Species Scylla tranquebarica Scylla serrata S. tranquebarica, Scylla serrata, Chanos chanos S. tranquebarica Scylla serrata
Culture period (days) 120 138 30
Expenditure (Rs) (Seed, feed, pond preparation, labour) 43,860 48,400 56,200
Production (tonnes) 0.78 1.14 and 0.7 tonnes of milkfish 0.56
Income (Rs) 1,57,200 2,61,200 1,22,850
Net profit/ crop (Rs) 1,13,340 2,12,800 66,650

(Source: Indian Council of Agricultural Research, 2000)

Top

Admin Login

Copyright © 2019. Developed & Maintained by Centre for E-Learning, Kerala Agricultural University