How to polyculture blue crabs

Blue crab is a kind of swimming crab that lives on the beach. It lives in mudflats or muddy beaches in the intertidal zone. How to carry out polyculture? Let's take a look at the mixed culture technology of blue crabs that I carefully recommend for everyone, hoping to help you.

Mixed culture technology of blue crab

1, shrimp. Such as China shrimp, Penaeus penicillatus, Penaeus monodon, Penaeus japonicus, Penaeus monodon and self-propagating white shrimp in ponds. The stocking specifications of shrimp seedlings require that the number of seedlings above 3 cm after temporary rearing is generally around 1000 ~ 2000/mu, which is faster than that in a shrimp pond at high tide. When the water temperature is suitable, you can start fishing after 1 month.

2. fish. The main species are: mullet, barracuda, black snapper, mudskipper and so on. The organic matter condensed in the pond is an excellent bait for these fish, and the amount of seedlings released generally ranges from 20 to 500 per mu.

3. shellfish. Mainly the mixed culture of some benthic shellfish, such as SINONOVACULA constricta, Meretrix meretrix, clam, etc. Taking SINONOVACULA SINONOVACULA as an example, the area of the beach where seedlings are released should be controlled below 20% of the pond area, and the coating of shellfish should be carried out in turn every year. After the flat central beach surface is deeply turned and leveled, seedlings can be released, and the amount of seedlings released per mu should be 30 ~ 50 kg.

4. seaweed. Co-culture of blue crab and Gracilaria in Taiwan Province Province (called Gracilaria lemaneiformis in Taiwan Province Province) is quite common. Mixed culture of algae can absorb and consume a lot of dissolved organic matter in water, increase dissolved oxygen in water, and is more conducive to the growth of economic animals such as blue crabs in the pool.

Matters needing attention in polyculture

1, the density of mixed culture should not be too high, and there should not be too many varieties. The main method should be to breed blue crabs, and the daily management method should also be carried out according to the method of breeding blue crabs. If mixed with other varieties, the density is too high, which will become a kind of interference and affect the growth of blue crabs.

2. When selecting polyculture varieties, it should be based on the pond conditions, especially whether the type of pond sediment conditions conforms to the habitat of the cultured varieties. For example, it is not advisable to breed varieties that are farmed across the year, especially fish varieties, which generally cannot overwinter in the pond. The casualties of transplanting will be great, and the only way is to improve the specifications of releasing seedlings so that fishermen can meet the conditions of polyculture before the arrival of low temperature.

Life attribute of blue crab

Blue crab is a kind of beach swimming crab, which lives in mud beaches or muddy beaches in the intertidal zone and likes to stay in puddles and crevices. There are many caves during the day and foraging around at night. Especially on the night of high tide, it is more active. Because of its clear eyes and sensitive antennae, it can move freely at night. In summer, the activities of blue crabs are more frequent. When the low tide is shallow, the mud bottom often hides for the summer. Sometimes you can see groups of blue crabs propping themselves up with their feet, leaving the hot beach and enjoying the cool in the dry heat. There is no activity in winter. When the weather is cold, burrows are dug near the low tide for winter. The size and depth of caves deepen with the increase of individual size and tidal zone, and sometimes the caves in the high tide zone can reach more than 1 meter. In the water, the blue crab moves to the left and right by the frequent paddling of the last pair of feet, but in most cases it drifts with the current and can quickly retreat when it is frightened or meets obstacles. It crawls on the beach surface with its feet, feeling sensitive and moving freely.

Blue crab is a kind of sea crab with wide temperature and salinity, and its survival temperature is 7 ~ 37? C, the suitable growth water temperature is 15 ~ 3 1? C, the best water temperature 18 ~ 25? c， 15？ Below c, the growth slows down obviously, and the water temperature drops to 7 ~ 8.5? C, stop eating and activities, and enter the state of dormancy and digging holes. Is the water temperature stable at 18? When the temperature is above C, the mother crab begins to lay eggs, and the young crabs frequently shell and grow up, and the water temperature rises to 37? Above c, the blue crab does not eat, and the water temperature rises to 39? At C, the crab's carapace appeared gray erythema, and its body gradually aged and died.

The survival salinity of blue crab is 2.6? ~55? , the adaptation range is 6.5? ~33? The optimum salinity is 12.8? ~26.2? (specific gravity10/0 ~1.021). It is difficult for the blue crab to adapt to the drastic change of salinity. The sudden change of salinity will cause two diseases, namely "red awn" and "white awn", and even death. Therefore, in the rainy season every year, due to sudden rainstorm or continuous rainfall in a short period of time, the salinity of artificial breeding ponds changes suddenly, which increases the mortality of blue crabs.

The blue crab has strong drought tolerance. After leaving the water, as long as there is a small amount of water in the gill cavity and the gill filaments are moist, they can survive for several days or dozens of days.

The feeding habits of blue crabs are very diverse, mainly animal foods. The food is mainly composed of mollusks and small crustaceans. In the stomach contents, there are often bivalve shell edges, twisted fragments, gastropods, broken screw shafts, residual limbs of square crabs and fragments of head and breastplate. Blue crabs often feed on worms, small fish and shrimp in the tidal flat, and sometimes plant stem and leaf fragments are found in their stomachs. The choice of food for cultured blue crabs is not strict. Small miscellaneous fish, shrimp, small shellfish (green clam, clam, clam, snail, etc. ), bean cakes and peanut cakes can be eaten. Blue crabs have the habit of killing each other and often prey on soft-shelled crabs that have just shelled.