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preface
The American anchovy is a large fish that can reach a length of up to 1.5 meters and weigh more than 30 kilograms. Their bodies are streamlined, dark green to bluish-grey on the back and silvery-white scales on the sides. Adult male anchovies usually have curved jaws and huge jaw hooks.
Affected by factors such as overfishing, water pollution, river development and habitat loss. Many anchovy populations have experienced significant declines over the past few decades. Therefore, the artificial farming of anchovy is imperative.
Biological properties
American anchovy is a broad-temperature anadromous migratory fish. Its suitable temperature range is 18 °C ~ 32 °C. Once sexually mature, they swim into certain freshwater waters to breed, and juvenile fish return to life in the ocean when they grow up.
American anchovy spend most of its time in the ocean, forming schools of fish and migrating to live in the sea with a water temperature of 7 °C ~ 13 °C. Their diet consists mainly of zooplankton and benthic small crustaceans, and occasionally prey on small fish.
American anchovies usually have around 2 years of sexual maturity, but it can take 3 to 5 years for males and 4 to 6 years for females. When they reach sexual maturity, they are between 48 cm and 53 cm long.
After sexual maturity, American anchovy returns to freshwater rivers for breeding, and the most suitable breeding water temperature is about 18.5 degrees Celsius. Some fish spawn as soon as they enter the freshwater, while others may need to travel more than 600 kilometers to reach their preferred spawning grounds for spawning.
During spawning migration, adults stop foraging and focus on tracing up to spawning sites. Once spawning is complete, they begin to migrate downstream and start feeding again.
Newly hatched fry in summer can be observed in rivers, usually forming schools of fish when they reach a body length of 2 cm to 3 cm and gradually moving downstream. During this time they feed mainly on benthic animals. Juveniles enter the ocean in autumn until they reach maturity.
Stocking conditions for artificial farming
1. Cultivate ponds
The incubation pond can be held indoors or outdoors. Indoor cement pools are usually 300 square meters to 600 square meters in size, and can be covered with plastic or glass greenhouses.
The outdoor pond is suitable for an area of 2,000 square meters to 3,300 square meters, and the water depth is 1.5 meters to 2.0 meters. When selecting a site, an area with abundant water sources, abundant dissolved oxygen and convenient drainage and irrigation should be considered, and 1 to 2 aerators of 0.75 kW to 1.5 kW should be configured at the same time.
The advantage of indoor cement pools is that environmental factors such as temperature and light can be better controlled, thus providing more stable growing conditions. Plastic or glass greenhouses can further protect the pool environment from outside disturbances and temperature fluctuations.
The advantage of outdoor ponds is that they can use natural light and natural environment, saving energy costs. When selecting a site, it is necessary to ensure that water sources are sufficient and that the water quality is rich in dissolved oxygen to promote the growth and health of fish. At the same time, a convenient drainage and irrigation system can ensure that the water level and quality of the pond are effectively controlled.
2. Clear the pond and disinfect
Qingtang drugs mainly include quicklime and bleaching powder. Quicklime is used to clear the pond, and 75 kg to 100 kg of quicklime is required per mu of water depth of 1 meter, and the whole pond is sprinkled. Bleaching powder is used for pond cleaning, and 15 kg to 20 kg of bleaching powder containing 30% chlorine is required per mu of water depth.
3. Cultivate biological food
On the day or day 2 after the pond is cleared, apply 100 kg to 150 kg of fully fermented organic fertilizer per mu to cultivate a suitable fertilizer and water environment. When plankton such as rotifers, clades and copepods are abundant in the water, the seed of American anchovy can be stocked.
Fry introduction and stocking
Researchers found that when releasing American anchovies, it is best to choose a size of more than 3 cm, and the stocking amount per mu can be controlled between 500 and 1,000. In order to ensure the safety and survival of the fry, the researchers used plastic bags to oxygenate the transport.
In 2009, 500 fry were introduced to the experimental base, and the survival rate reached 200. Then, in 2010, researchers introduced a further 3,000 American anchovy fry, with a survival rate of more than 90%.
These data show that the experimental base has achieved some success in fry stocking. With appropriate stocking specifications and transport measures, researchers are able to improve the survival rate of fry and lay a good foundation for subsequent development of farming.
In order to maintain the stability of the survival rate of seedlings, researchers should also continuously improve breeding techniques and management methods to ensure the healthy growth of fry.
The introduced American anchovy fry performed well in adapting to the new environment, with survival rates above 90%. This shows that the American anchovy has a strong adaptability to the breeding environment, which provides strong support for researchers to promote and develop the American anchovy culture locally. This also lays a solid foundation for further expanding the scale of aquaculture and increasing production.
Aquaculture management
1. Bait and feeding
The fry that have just come down the pond feed on the larvae of small clades and copepods, and are regularly fed with fresh clades. To encourage the fry to float and feed, a 25-watt light bulb can be installed on the surface of the water at night to attract the fry.
When the fry grow above 5 cm, their active feeding ability is enhanced, and it is the best time to start swarming and then switch to domestication. Usually tamed at night, the American anchovies fry's phototropism makes use of the light that the fry gather at the surface of the water under the light.
When feeding, acoustic stimuli can be used to lure the anchovy to float and feed. Usually after about 3 to 5 days of training, the fry are able to adapt to floating feeding.
Generally, anchovies are fed with slow sinking or floating granular bait, and the crude protein content of the bait is required to be more than 40%. Feeding is given 3 to 4 times a day, starting with a small amount of bait to induce the fish to feed, and then gradually increasing the feeding volume after the fish are in the group. Wait until most of the fish are full before reducing the amount of feeding.
The effect of anchovy on the domestication of bait has a more obvious effect on feeding performance than other fish, so it should be carried out slowly when feeding bait to induce fish to grab food to improve the utilization rate of bait. As the fish grow, the particle size of the feed pellets gradually increases.
American anchovy is a natural and active fish, they swim in circles throughout the breeding process, so the energy consumption is greater and the feed utilization efficiency is low.
The quality of the feed in anchovy farming is critical, and pelleted feed needs to be fed with a protein content of at least 40%. Anchovy prefers to feed on smaller particles that are floating or slow, so the feeding method should be a small number of multiple times, and the feeding material should be selected with a smaller particle size.
2. Water quality control
In the process of anchovy culture, the water temperature should be kept between 20 °C and 32 °C, the dissolved oxygen concentration should be kept above 5 mg/L, and the pH value should be suitable for 7.8 to 8.5. Through experiments, it was found that the anchovy tolerated poor low-oxygen environment.
The anchovy is a fast-moving fish that swims fast for life and always swims day and night. The rapid swimming of anchovies requires a large supply of dissolved oxygen, so meeting the oxygen needs of anchovies is the key to successful farming.
In actual production, it is common for suffocation and death of anchovies due to lack of oxygen. It is worth noting that the anchovy does not float in the absence of oxygen, which increases the difficulty of management.
Therefore, it is important to strengthen daily dissolved oxygen monitoring to prevent deaths caused by hypoxia. The dissolved oxygen concentration of aquaculture water should be kept above 5mg/L, especially in the high temperature season or rainy weather, the dissolved oxygen content should not be less than 6mg/L.
3. Wintering management
After practical verification, American anchovy has a wide range of temperature adaptation, and we use two ways to winter: indoor greenhouse and outdoor earthen pond. This important finding suggests that U.S. anchovy farming can be widely scaled up in our region and that it can also reduce the cost of farming facilities.
Compared with indoor greenhouses, outdoor earthen ponds have certain advantages, not only to make full use of natural light and natural environment, but also to reduce facility investment and maintenance costs.
In outdoor farming, we need to pay attention to choosing the right earthen pond location to ensure sufficient sunlight exposure and water supply. According to climate change, adjust water temperature and water quality management in a timely manner to maintain a suitable growth environment. Outdoor aquaculture also needs to strengthen the monitoring of feed management and disease prevention and control to ensure the health and growth of anchovy.
Through the comparative study of two wintering methods in indoor greenhouse and outdoor earthen pond, the breeding technology can be further improved and the breeding efficiency can be improved. Compared with indoor greenhouses, the promotion of outdoor aquaculture methods also helps to protect the environment and sustainable development, in line with the development trend of modern aquaculture.
According to different aquaculture needs and geographical conditions, choosing the appropriate aquaculture method can maximize the breeding potential of American anchovy and bring greater economic and environmental benefits to the aquaculture industry.
4. Precautions
American anchovy has the characteristics of being lively and lively, its scales are easy to fall off, and it is also very sensitive to external stimuli responses. They are susceptible to shock and injury, or death from illness following a stress response.
In the process of graded cultivation and counting, it is necessary to carry water, and the movements should be meticulous and gentle. Try to avoid or reduce mechanical damage and reduce dragnet operation to reduce stress response. This is the key to improving the survival rate of anchovy farming.
The transport of anchovy fry is a difficult task, so the transport specifications should not be too large. Generally speaking, seedlings with the size of summer flowers of 2cm~3cm have the highest survival rate when transported.
During fishing and transportation, it is necessary to carry out water operations and try to choose a low-light environment to reduce the scare of American anchovy.
Care needs to be taken to avoid injuries caused by jumping fish, or emergency spasms that can lead to death. During transportation, attention should be paid to controlling temperature and density to reduce the mobility of fish and reduce the risk of mechanical damage.
Promotion prospects
The success of anchovy farming in the United States mainly depends on the cultivation of biological food in the early stage and the domestication of artificial compound feed. In the process of artificial farming, American anchovy shows a lively swimming in a non-stop circle, has a high demand for dissolved oxygen, and is highly susceptible to stress, prone to hypoxia and death due to injury. In addition, the transportation of anchovy also faces certain difficulties.
Through facility improvements and experience, these constraints can be overcome to achieve large-scale farming of anchovy in the United States. After experimental verification, American anchovy is suitable for expansion as a freshwater characteristic species. At the same time, the American anchovy is an anadromous migratory fish, so it can carry out mariculture experiments and artificial breeding experiments.
epilogue
U.S. anchovy farming is a challenging, but potential, farming business. During the breeding process, it is necessary to pay attention to the quality of feed and feeding methods to ensure the healthy growth of fry. Managers need to pay attention to environmental factors such as water quality, dissolved oxygen and temperature to provide suitable breeding conditions. Through reasonable transportation and operation, stress and damage are reduced, and the survival rate of anchovy is improved.
In order to promote anchovy farming in the United States, continuous improvement of facilities and technologies is necessary. At the same time, the use of local water resources for mariculture experiments and artificial breeding experiments can expand the scale of aquaculture and enrich variety resources. Through continuous practice and experience accumulation, we can break through the problems encountered in aquaculture and promote the development of the American anchovy aquaculture industry.
bibliography
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ZHAO Liang,WANG Xiaojun,WANG Limin. Study on feed formulation and application of anchovy culture[J]. Fisheries Science and Technology Information,2014,(4):93-95.]
WANG Jiguo,WANG Lihua. Research on disease prevention and control technology in anchovy culture[J]. Aquaculture,2012,(6):30-33.]