 |
| How to Cultivate Crab |
The growing market share of mangrove crabs (Scylla serrata) both at home and abroad is a challenge to continuously increase production. By relying solely on production from nature / catches, it is clear that the continuity of production can be expected. For this reason, there is a need to cultivate crustaceans that have high economic value.
The business of mangrove crab cultivation must be supported by the availability of land that is free of pollution, seeds and management capabilities both technically and management. Maintenance land can use traditional ponds as used to maintain shrimp or milkfish.
Mangrove Crab Type
Types of mangrove crabs that have high economic value include:
- Scylla serrata, this type has a grayish color to reddish green color.
- Scylla oceanica, green in color and there are brown lines on almost all parts of the body except the abdomen.
- Scylla transquebarica, greenish to black with a slight brown line on the swimming leg.
Of the three types of crabs mentioned above, Scylla serrata at the same age are generally smaller than the other two types. But in terms of price and asking the buyer, the first type is superior.
Mangrove Crab behavior and habits
In general, the behavior and habits of mangrove crabs that can be observed are as follows:
1. Like to soak in the mud and make a hole in the wall or a maintenance pond. By knowing this habit, then we can plan or design a place of maintenance in such a way that the possibility of escaping crabs is kept as small as possible.
2. Cannibalism and attack each other, this trait is most striking in the crabs so that it can harm the handling of life and cultivation. Because of its mutually attacking nature, it will lead to low life graduation and reduce farm productivity. This cannibalism characteristic is the most dominant in male crabs, therefore monosex cultivation in crab production will provide better survival.
3. Molting or changing the skin. Like crustacean animals, crabs also have properties like other crustaceans, namely molting or changing the skin. Every time the skin changes, the crab will experience large carapace growth and weight. Generally skin changes will occur around 18 times starting from instar to adult stadia. During the process of changing the skin, crabs need energy and movement that is strong enough, so for adult crabs who experience skin changes need a large enough area.
The growth of crabs will look more rapidly when young, this is related to the frequency of skin changes during the initial stage. The period and type of frequency of skin change is important in conducting a cultivation business pattern that is related to the design and construction of the container, the type of cultivation and its management.
4. Sensitivity to Pollutants
Water quality is very influential on crab survival. Decreased water quality can occur due to excess decaying leftover food. If the crab condition is weak, for example, it does not react quickly if it is held or the stomach is empty if it is split, this is likely due to the decline in flow. To avoid the worse effects, immediately move the crabs to other maintenance sites where the water conditions are still fresh.
Location of Cultivation
Crab maintenance ponds are cultivated to have a depth of 0.8-1.0 meters with water salinity between 15-30 ppt. Muddy pond ponds with sandy clay or silty loam texture and tidal differences between 1.5 -2 meters. In addition to the requirements as mentioned above, in principle milkfish and traditional shrimp maintenance ponds can be used as crabs for maintenance.
Factors that need to be considered in the selection of crab maintenance sites include:
- The water used is free from pollution and the amount is sufficient.
- There is sufficient feed and continuity guaranteed.
- There are facilities and production infrastructure and marketing.
- Skilled workers and masters of crab cultivation techniques.
Pond Design and Construction
If the treatment of crabs during the maintenance period is not good, such as: water quality is not considered enough, food is not sufficient then when the crab reaches mature biological conditions the egg will try to escape, by climbing the wall / fence or by making a hole in the embankment. To avoid this, the dike and sluice construction need to be considered as carefully as possible. The bamboo cane fence can be installed on a dike or from waring, this will reduce the possibility of crab escaping.
Installation of bamboo kere fences or sturdy bunding wares (2-4 meters wide) is carried out on the edge of a section with a height of about 60 cm. In ponds that are not solid, the fence is installed on the base of the embankment with a minimum height of 1 meter.
Stocking
At the location of catching crabs from nature, during the season the seeds are traditionally cultivated by farmers only relying on crab seed crabs that enter naturally at high tide. After a few months, selective harvesting begins by picking up crabs that are ready to sell. Can also crabs that have reached that size are released back into the enlargement plot to get a larger size or overweight.
In polyculture with milkfish, the size of crab seeds weighing 20-50 grams can be stocked with a density of 1000-2000 head / ha, and the milkfish weighing 2-5 grams are stocked with a density of 2000-3000 head / ha. In the cultivation of monoculture system, the size of the crab above is stocked with a density of 5000-15000 / Ha.
Egg Laying Crab Cultivation
The crabs that have just been harvested from the pond, can be further cultivated to improve the quality of female crabs not laying eggs or laying eggs not yet fully into full laying eggs with more intensive cultivation methods. With conditions laid out it will increase its added value. Because the price of female crabs lay eggs can reach 2-3 times the price of crabs does not lay eggs, so this will greatly help increase the income of fishermen farmers.
The methods used for the purpose of laying crab production are of two types, namely: with a confinement system and floating cage system.
1. Confinement System
Confinement can be made from bamboo material made into a series. Thick bamboo bar 1-2 cm with 1.7 meters long. Bamboo blades are arranged regularly so that they form kere or a kind of fence. The kere is then installed on the pond channel extending to the edges, if it is installed in the pond, so that it is placed in a relatively deeper part and gets enough water replacement.
Kere or bamboo fence is plastered as deep as 30 cm with the bottom made more tightly aiming so that the crabs do not pass. For placement of confinement in the pond channel, the size is adjusted to the width of the channel and so as not to disturb the flow of the pond channel. For a larger scale, you can use a pond map with an area between 0.25-0.50 hectares with a fence around the bamboo kere or from waring. the bamboo fence is plunged as deep as 30 cm and the smooth part is facing inward with the intention that the crabs cannot climb because this part is slippery.
2. Floating cages
In addition to using confinement, the cultivation of egg crabs can also use floating cages. Floating cages are made from a series of bamboo blades such as making kere, then the kere has been assembled into a box, the size of which is adjusted to the location where the floating cages will be placed. Furthermore, on opposite sides, buoys are installed which are made of pieces of bamboo that are still intact or from other materials. The placement of this floating cage in the water turns occurs fairly / well, such as on the channel, river bank and other places that meet the requirements as mentioned above. In this cultivation effort with floating cages the density can reach 20 tails / m2, with this density will increase the survival of the crabs that are maintained. The size of ready to harvest crabs lay around 200 gr / head.
The longest crab production process takes around 5-14 days or depends on the initial size of the stocking. In short, this maintenance period is also possible because female crabs that are stocked with a weight of about 150 grams usually contain eggs.
Fattening Business
Cultivation business besides being used as egg crabs is fattening. the fattening business process is the same as the cultivation of egg laying crabs. You can use bamboo cages or floating bamboo cages. The obvious difference lies in the crabs that are kept. The crabs that were kept in this fattening business were export-sized crabs from male and female genders who were still porous. The period of fattening is around 5-10 days, the crabs will become fat and contain good maintenance. If the maintenance is continued for the female sex, it will even become an egg crab. To avoid mortality due to fights between males and females, maintenance should be carried out monosexically.
Feed
Various types of feed such as: trash fish, chicken intestine, cow skin, goat skin, snails, rice field snails, etc. from the type of feed, fresh trash fish is better in terms of physical and chemical and the opportunity to be eaten faster because it is so stocked will not be eaten immediately by crabs.
Feeding for enlargement efforts is only a supplement with a dose of about 5%. As with the crab laying and fattening business, feeding should be considered with a dose of between 5-15% of the crabs that are maintained. The willingness to eat young crabs is usually greater, because in this period it takes a sufficient amount of food for the growth and process of changing the skin. Willingness will decrease when the crabs are laying eggs, and the peak after the eggs come out seems crabs fasting.
Post Harvest of Mangrove Crab
One of the things that is beneficial in handling crabs after being harvested is their ability to survive long enough in conditions without water. However, poor handling will reduce the health condition and can cause death.
If the crab after being harvested is directly put into the basket by tying the claws, the leg of the road and the swimming leg which is a fairly strong motion device, then the crab will stick together with each other. Such conditions will cause physical damage to the body of the crab and affect physiological conditions which can eventually lead to death. To overcome this situation, newly caught crabs must be fastened before being put in a basket.
How to tie the newly captured crabs can be done as below:
- Binding of the two claws and all of his legs
- Only tie the claws with one rope
- Binding each claw with a separate rope
straps can use rope or other types of rope that are strong enough. After the crab is tied, the binding of the claws and the binding of the legs will facilitate handling and transport
Crab handling that has been arranged in a basket that needs attention is to maintain temperature and humidity. Try to keep the temperature no higher than 26 ° C and good humidity is 95%. The method that can be done to maintain the ideal temperature and humidity for the survival of crabs during transport is: smear the crabs into brackish water (15-25 ‰ salinity) for approximately 5 minutes while shaking so that dirt is released. After the crab is rearranged in the container. cover the container with a wet gunny sack.
EmoticonEmoticon