Crab Seed Production Techniques

Crabs are one of the aquatic species with high nutritional\r\nand economic value. The successful production of artificial crabs\r\ncontributes to the development of mud crab farming models in many localities\r\nthroughout the country.

Water treatment

The water used has a salinity of 25 ‰ or more. After\r\nfilling the sedimentation tank with water, apply potassium permanganate\r\n(KMnO4), concentration of 1.5 - 2 ppm (1.5 - 2 g / m3). Aeration of\r\nsedimentation tanks continuously for 30 minutes, followed by using CaCO3 powder\r\n(or Dolomite lime) with concentration of 50 g / m3 of water, continue to aerate\r\nvigorously for another 30 minutes. Then turn off the aeration to let the\r\nwater settle all suspended organic matter. Whenever you see the clear\r\nwater, pump to another tank through a filter bag to treat Chlorine.

Raising parents clap

Preparing the tank: The mother rearing tank is usually a\r\ncement tank, a sand compartment occupies 1/3 of the bottom of the tank, the\r\nthickness of the sand layer is about 5-7 cm, the remaining space is arranged\r\nwith facing tiles. sheltered crabs. Feed water has a salinity of 30-32 vỗ. In\r\ntanks fitted with moderate aeration.

Choose mother crabs: Choose the females weighing 450 - 600\r\ng, fully legged, clean and full of bricks, preferably crabs from the sea (crabs\r\ncaught by the rakes). Stocking crabs with a density of 2 fish / m2.

Care: Feed the mother 2 breakfast and afternoon. Feed\r\nfor crabs is paraplegia, nugget, oysters or blood cockle.

Regularly check and remove uneaten food and waste siphons\r\nfrom the tank.

Change the water for the mother tank every 2 days,\r\ncompletely changing 100%. Each time change the water catch the mother out\r\nof the tank, scrub and bathe with iodine (about 7 drops in a bucket containing\r\n20 liters of salt water) for about 5 minutes and then transfer the crab to the\r\nnew water tank.

The period of raising is about 15 - 20 days, the mother lay\r\neggs.

Incubate and hatch

Hatching eggs: When the mother lays eggs, take them out and\r\nincubate in the incubator. Replace the whole water for crabs\r\neveryday. Iodine bath with Iodine, concentration of 15 ppm for 1 minute\r\nbefore releasing. Incubation period is about 10-12 days, the crabs hatch\r\ndepending on the water temperature high or low.

For hatching: When there are a few zoea larvae in the\r\nhatching box (usually on the 10th day), the mother will be transferred to\r\nhatching tank. Ordinary hatching tanks are plastic or composite tanks with\r\na volume of about 200 - 500 liters, the water supplied to the hatching is\r\nsimilar to the water supplied to the nursery tanks, moderate aeration layout to\r\nensure adequate oxygen but not too strong affecting the ovaries of the mother.

Nursery rearing\r\nlarvae

Larval rearing tanks can be composite tanks or cement\r\ntanks. 1 day before the mother hatched, supply water to nursery tanks,\r\ninstall aeration and treat chemicals. When water is finished, aeration is\r\ninstalled, using EDTA 5 ppm to precipitate all heavy metals in 30 minutes.

The feed for zoea 1 larvae is a synthetic feed and Artemia\r\nsprung umbrellas, feeding 1 hour after hatching.

When hatching eggs must be removed immediately by the mother\r\nto minimize contamination by feces and egg silk of the mother\r\ndischarged. Reduce the aeration for all the dirt to settle to the bottom\r\nof the tank, and use a small stick to remove all the floating egg membranes on\r\nthe face, then clear all the dirt.

Conducting larvae collection with fine racket, bathing\r\nthrough seawater mixed with iodine and then put into the rearing\r\ntank. Stocking density of larvae in rearing tanks: 150 individuals /\r\nliter.

Larvae stage 1: Feeding Artemia larvae even though the 7th\r\nday. Feeding 4 times a day: 6h, 12h, 18h, 0h.

Normally by the 5th day, the siphon changes water, if it is\r\ntoo dirty, siphon can be changed on the 3rd day. The level of changing the\r\nwater is not more than 30%.

Larvae stage 2: When there are zoea 5 larvae in the nursery\r\ntank, the leveling of new tanks is conducted. The amount of food remains\r\nthe same, while adding synthetic foods depending on the ability of crab larvae\r\nto catch prey.

When larvae transition to megalops stage, stop feeding\r\nArtemia, switch to processed / synthetic feed. Feeding 6-8 times a day,\r\nthe amount of feed depends on the ability to catch the larvae. When the\r\nmegalops move to the bottom, they need to spread mussel shells in the nursery\r\ntank to give them shelter to avoid the phenomenon of eating each other when\r\nmolting. A few days later continue to attach plastic objects to the tank.

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Around 26 - 28 days, the crabs can be collected and\r\nexported.

Source : http://www.thuysanvietnam.com.vn