In early May 2016, Jiangsu Hongze Lake Hairy Crab Industry Co., Ltd. introduced 39,000 Australian freshwater lobster fry (about 2 cm/tail) for experimental breeding at the aquatic base of Laozishan Town, Hongze County. The author analyzes and summarizes the breeding process and results for reference
Australian freshwater lobster (Cherax quadricarinatus), scientific name four-ridge light shell nanao shrimp, also known as red crayfish, native to Australia, the shape resembles the lobster in the sea, is one of the world's most valuable freshwater economic shrimp species. The shrimp has a brownish green body color, and the outer tip of the mature male shrimp has a membranous bright red band, so it is also known as the red cet shrimp. Australian freshwater lobsters are called freshwater lobsters because they are large and resemble lobsters in the sea, and only live in freshwater. Individuals generally weigh 100-200 grams, with the largest individuals in Australia weighing up to 500 grams. Australian freshwater crayfish have a variety of diets, ranging from artificial compound feed, bran, melons, fruits and vegetables, to plankton and organic detritus.
In early May 2016, Jiangsu Hongze Lake Hairy Crab Industry Co., Ltd. introduced 39,000 Australian freshwater lobster fry (about 2 cm/tail) for experimental breeding at the aquatic base of Laozishan Town, Hongze County. After 5 and a half months of outer pond farming, at the end of October 2016, a total of 2360 kg of Australian freshwater crayfish were harvested, with a yield of 158 kg per mu, with a survival rate of 35.9%, and the average size of finished shrimp was 85 g/tail, of which the average size of male shrimp was about 100 g/tail, and the average size of female shrimp was about 70 g/tail.
Farming experiments have shown that the australian freshwater crayfish live in the range of 5-35 °C, the suitable growth temperature is 13-28 °C, when the water temperature exceeds 13 °C, it will start feeding, and the water temperature exceeds 30 °C, which will inhibit growth.
Freshwater crayfish shrimp breeding pond is rectangular, with an area of 5-10 acres, a water depth of about 1.5 meters, a sediment bottom at the bottom of the pond, and a good water retention in the shrimp pond. 50 cm high escape facilities should be built around the pond.
The inlet and outlet of the shrimp pond should be equipped with filter silk nets to prevent the entry of predators such as wild trash fish, and the pond should be planted with aquatic plants such as Ile algae and water leeks. A certain number of bamboo tubes, stones, tiles and other shelters should be placed at the bottom of the pond for lobsters to hide and roost.
The shrimp pond is sprinkled with 30 catties of tea seed cake per mu, and the loach, catfish, blackfish, snakes, rats and other predatory predators in the pond are completely removed for 15 days, and then disinfected with quicklime water, with a dosage of 100 kg per mu.
About 10 days before the stocking of shrimp fry, about 200 kg of decomposed organic fertilizer is stocked per mu of shrimp pond to cultivate zooplankton, so that shrimp fry can be stocked with sufficient suitable biological bait.
Australian freshwater crayfish fry stocking should choose sunny morning or evening, try to avoid rainy days to release seedlings. Before releasing the seedlings, use a small amount of pond water to slowly add to the seedling container to adjust the water temperature, until the water temperature in the container is close to the temperature of the pond water, and then put the shrimp fry into the pond to prevent the shrimp fry from being affected by the water temperature difference, causing a stress response, affecting the survival rate and growth and development.
The stocking size of shrimp fry is generally 3-5 cm, the stocking density is 5000-6000 per mu (our experimental breeding stocking density is 2600 per mu), and the shrimp fry stocking in the pond is uniform.
Three days after the seedlings are released, the shrimp fry are mainly red worms in the pond supplemented by small ground trash fish and minced meat; then fed for about 1 month small trash fish, foot meat and artificial compound feed, and also fed some fruits and vegetables. This is also based on soybean meal, bran, rice bran and other raw materials in a certain proportion, adding high concentrations of biological bacteria to make a fermented feed for daily feeding, the effect is very good.
<b>Generally, medium and small shrimp are fed according to 15%-25% of body weight, and adult shrimp are fed 5%-10% of body weight</b>
The daily feeding amount is based on eating, eating and leaving no residual bait. Generally, medium and small shrimp are fed according to 15%-25% of body weight, and adult shrimp are fed 5%-10% of body weight. Feed once a day in the morning and once in the evening, and 70%-80% of the daily feed in the evening, the feed should be placed on the shallow water edge of the pond.
The water quality is mainly composed of fertilizer water in the early stage, with a transparency of 25 cm, and in the middle and late stages, the transparency is 30-40 cm by adding water and changing water at intervals of 15 days. From mid-June to mid-September, microbial agents and bottom-up products are used, and the aerator is started for 1-2 hours at noon on a sunny day to increase the dissolved oxygen in the pool and eliminate harmful substances such as ammonia nitrogen in the water. Use quicklime regularly, at intervals of 15-20 days, and use 5 kg of quicklime per acre of water depth of 1 meter to keep the pool water slightly alkaline.
Due to the rapid growth of Australian freshwater lobster, strong metabolism, large oxygen consumption, shrimp pond water quality should often be kept fresh, ponds should be planted with aquatic grasses (such as Ele algae, water leeks), so that the water quality to achieve a refreshing, pool water transparency control at about 35 cm, and enough dissolved oxygen, it is recommended to install an aerator or microporous oxygenation equipment.
In the daily management, it is necessary to check and patrol the pond diligently, remove the moss in the pond in time, and often check the filter net of the inlet and drainage outlets to prevent the shrimp from escaping after the filter is damaged, especially to prevent the entry of river crabs, crayfish, yellow eels, grass carp and other predators. When encountering thunderstorm sweltering hot days, even cloudy days of bad weather, to reduce or stop feeding, when the weather is too hot and too cold, should be appropriately deepened pool water to stabilize the water temperature, at the same time, but also often observe the feeding and activity of freshwater lobster growth, shelling and other situations.
Australian freshwater lobsters are highly resistant to disease, and no outbreak or epidemic diseases have been found since their introduction, but with the improvement of intensive aquaculture, disease prevention and control work cannot be taken lightly! Prevention and control work should be based on prevention, and the surface of the body can be disinfected before the seedlings are planted in the pond to prevent the pathogen from being brought into the pond.
When the water quality changes and there are more microorganisms in the water, there will be many yellow or brown attachment organisms on the exoskeletons such as the head and chest of the shrimp. After microscopic observation, most of them are ciliates of the mycoccids, polycondenia, bellworms and so on. These ciliates inhabit the exoskeletons of adult shrimp in the middle shrimp, live symbiotically, form rough branches and warts on the body surface, increase the burden and pressure of the host, lead to slow movement, reduced feeding, molting difficulties, if the dissolved oxygen in the water is low, it is more likely to lead to lack of oxygen and suffocation, and even death. General parasites can be removed by combining copper sulfate with ferrous sulfate (5:2) 0.5-0.7ppm or hanging bags, or can be soaked with 15-25ppm formalin or saturated brine.
Gastrointestinal diseases are mostly caused by the intake of spoiled bait, so the bait requires freshness and does not use moldy bait. When using legumes as bait, it must be warmed to remove antitrypsin and facilitate the absorption of plant protein.
For the choice of shrimp bait in this regard, especially the feeding of fermented feed, the benefits are as follows:
(1) Strong food attraction: fermented feed has a special flavor, excellent palatability, fast feeding speed, shrimp eat more.
(2) Good intestine: improve the intestinal environment of shrimp, the intestine becomes significantly thicker, promote the digestion and absorption of feed, less feces and not smelly, feces into strips.
(3) Good water quality: effectively inhibit the growth and reproduction of harmful algae such as cyanobacteria, improve water quality, and make water quality beautiful and durable.
(4) Good bottom quality: effectively decompose residues such as feces and undigested bait at the bottom of the pond, and it is not easy to return to the bottom.
(5) Good liver: reduce the burden of the liver, enhance the immunity of shrimp, reduce the incidence of disease, and greatly improve the survival rate of shrimp.
(6) Less stress: less stimulation stress for rain, thunder, light, pond, sound, etc., and the vitality of shrimp can be seen when the material is lifted.
(7) High rate of return: improve the conversion rate of feed utilization, reduce drug use, shorten the breeding cycle, and improve the comprehensive rate of return.
Although Australian freshwater lobsters can tolerate low oxygen, surviving in a low-oxygen environment for a long time will reduce immunity and affect feeding, shelling and growth. Therefore, aeration facilities should also be available in the culture ponds. If hypoxia is found, the aerator should be turned on in time to ensure sufficient dissolved oxygen in the water.
Australian freshwater lobsters are more sensitive to pesticides, and fish drugs such as pyrethroids can also cause the death of Australian freshwater lobsters. If farmland water is used to irrigate ponds, it is strictly forbidden for field water to flow into shrimp ponds during the application of pesticides in the farmland. There are also accidents in which people blindly apply enemy insect pesticides with the intention of killing predatory creatures and causing serious deaths of lobsters.
Australian freshwater lobsters generally reach 75-200 grams per freshwater lobster after 160-180 days of culture (more than 50 grams can be marketed).
Australian freshwater lobsters are stocked and harvested in the same year, and can generally be harvested in dry ponds or purse seines when they grow to adult shrimp. If it is listed in stages and batches, it can be fished in a ground cage, or it can be caught in a trap cage, that is, a bait is placed in the cage, and the shrimp cannot be re-entered. The entire harvesting process should be completed before the water temperature drops to 15°C.
Shrimp cage trapping: put trap cages in the evening, put some bait in the cage appropriately, close the cage in the early morning, or close the cage several times at night, this method is convenient and easy to operate, and it is convenient to provide live shrimp to the market successively.
Reverse water capture: Freshwater lobsters have a strong reverse water nature, draining 30% of the pond water before catching, filling it with new water in the evening, and rounding it up at the end of the inlet water. Three consecutive times, the catch rate can reach 70%.
Australian freshwater lobsters are highly resistant to drying, second only to crabs. It is convenient for the long-distance transport of live shrimp, and if the transport quantity is large or the transport distance is long, it is transported with baskets and boxes woven of wicker or bamboo or foam boxes with holes on all four sides. Rinse the shrimp before transport, tie the tongs, and put 10-15 kg per carton. Put a small amount of water weeds on the upper part and tighten the lid of the box with wire clamps. Sprinkle a small amount of clean fresh water on the way to keep the commercial shrimp in the box moist. When shipping, pay attention to light handling, when the temperature does not exceed 28 ° C, the survival rate of transportation within 24 hours reaches 100%, after the commercial shrimp is transported, it is necessary to scatter the freshwater lobster in cement or ice buckets or 8-10 ° C refrigerated tanks, and the water remains humid, and avoid a large number of lobsters concentrated in the water container, so as not to die due to excessive density, lack of oxygen in the water.
39,000 seeds were introduced, the weight of the harvest was 1180 kg, the yield was 79 kg per mu, the average size was 85 grams, the price was 100 yuan per kilogram, and the output value was 118000 yuan.
Expenditure is 88,500 yuan, of which 58,500 yuan is shrimp seed, 6,000 yuan is feed, 1,000 yuan is fertilizer medicine, 1,500 yuan is water and electricity bills, 12,000 yuan is pool rent, 1,500 yuan is fenced, 7,000 yuan is artificial, and 1,000 yuan is miscellaneous. The total profit is 29500 yuan, and the profit per mu is 1967 yuan.
From the actual results of breeding, a total of 2360 kg of Australian freshwater lobster finished shrimp were harvested, with a yield of 158 kg per mu, with a survival rate of 35.9%, and the average size of finished shrimp was 85 g/tail. Such breeding results are not good, the survival rate is not high, and the comprehensive benefits of aquaculture need to be improved. The author analyzes the reasons for this, and the following points are worth noting:
(1) The size of the shrimp fry is small and uneven: the size of the introduced seedlings is 1.5-4.5 cm, and the survival rate of small shrimp fry is very low.
(2) Incomplete pond clearance: The pond also has yellow eels, crucian carp, carp and crabs, which will prey on Australian freshwater lobster fry, greatly affecting the survival rate of shrimp fry.
(3) Aquatic grass is too lush: the density of aquatic grass planted in the early stage is too high, and the daily cleaning and management of aquatic weeds is not paid attention to, resulting in 2/3 of the pond covered with aquatic grass in the later stage, Australian freshwater lobster is not convenient to come out to eat, some shrimp are not good at feeding, the size specifications are uneven, and the total output cannot go up. Therefore, the total cover of aquatic grass should not exceed 1/3 of the total area of the pond, and the growth of aquatic grass should be in rows, which is conducive to shrimp coming out for active foraging.
(4) Raising other species to improve the comprehensive benefits of aquaculture: In 2016, Australian freshwater lobster farming was exclusive, there was no polyculture of other aquaculture species, and the production potential of good water bodies was not fully utilized. If you raise some green shrimp, silver carp, silver carp and yellowtail, these aquatic substances do not compete with Australian freshwater crayfish, but also make full use of the biological bait in the water body, increase production and increase efficiency, can play a scavenger effect, improve water quality, and get more in one fell swoop.