|
Mud crab hatchery technology
Procurement of berried crabs Female crabs of both species carrying egg mass are caught in considerable numbers in the inshore region. However, berried females of smaller species (S. serrata) do occur in the brackishwater areas including the traditional fish/shrimp culture ponds and mangrove water bodies. Though they are available throughout the year in the wild, considerable number of berried females are caught during the peak breeding season. The second source of berried crabs is from the crab culture ponds, where both the sexes of larger species (S. tranquebarica) and smaller species (S. serrata) mature, mate and female crabs become berried. The third source is by the inducement of maturation in the captive adult female crabs held in a hatchery complex. The removal of one of the eye-stalks by electrocauterisation would help in the development of ovary and subsequent appearance of berry within a period of 15 days from the time of eyestalk ablation. Also Read: The biology of the mud crabs Transport of berried crabs For short-time transportation (1-6 hours), the berried crabs can be kept submerged in seawater (salinity: 30-35 ppt) / brackishwater 15-25 ppt) and placed individually in 10-litre capacity containers such as plastic buckets and metal tins. For longer journeys of 7 to 24 hours, 50-litre capacity containers with proper provision for aeration are to be used They can be sent safely by air/rail/road to their destination. Hatching As part of the healdi management, the berried crabs obtained either from wild or from the culture pond should be treated with 10 ppm malachite green/methylene blue dipping for 5 minutes, which would ensure die eradication of harmful bacteria from the eggs. This treatment would enhance the hatching rates The berried females should be kept individually in 500-litre capacity fibreglass/cement tanks covered with black cloth to cut the light. Before liberation of larvae, the abdominal flap of mother crab makes frequent jerking movements and the egg mass gets loosened. Also, the jabbmg of walking legs over the egg mass takes place, before hatching first zoea larvae from the eggs Normally, the release of larvae occurs in the early morning hours, which is a continuous process, lasting for 3-5 hours The liberated zoea larvae are phototactic, i.e. attracting towards the light. Also Read: How is oyster farming done Larval rearing Stocking of larvae The first zoea larvae should be stocked at a rate of 200-400 number per litre in 2-ton fibreglass/cement larval rearing tanks, which contain filtered seawater and aeration facility. Rearing medium The filtered seawater having a salinity range of 30-35 ppt and water temperature of 27-29° C should be used. Water should be exchanged daily at a rate of 80 %. More Guidelines Visit: How To Raise Crabs Resources: - Jstor You May Also Want To Raise: |
How To Raise Crabs Contact Us Terms of Use Privacy Policy About Us FAQ Site Map