In addition, large yellow croaker is a warm and humid nearshore migratory fish that often lives in the middle and lower layers of water within 60 meters in depth, making it extremely difficult to catch.
But compared with bluefin tuna, yellow croaker is still far behind.
The most important thing is that yellow croaker has now been artificially cultivated.
Although the breeding conditions are very harsh.
The breeding pond should be a rectangular pond running east-west, with an area of more than 6 mu, and be able to maintain a water depth of more than 2.5 meters. The bottom of the pond should be inclined at a certain slope towards the drain outlet, and the bottom should be sandy and muddy.
The breeding location should have convenient transportation, a quiet environment, abundant fresh water resources, and convenient water supply and drainage.
Generally, a large yellow croaker breeding pond needs to be equipped with at least 2 1.5-kW waterwheel-type aerators and 1 1.5-kW jet-type aerator.
In addition, the production environment around the breeding pond needs to comply with the relevant provisions of the "Environmental Standards for Pollution-Free Aquatic Products Production Areas", and the water quality for breeding water must comply with the "Fishery Water Quality Standards" and "Water Quality for Pollution-Free Food Freshwater Breeding" and other relevant regulations.
But no matter how harsh the conditions are, humans will always find a way to make them happen.
However, with the success of yellow croaker breeding technology in recent years, the price of yellow croaker has not dropped much.
Whether it is the price of farmed yellow croaker that has been desalinated or the real seawater yellow croaker, the price is extremely high.
In fact, breeding large yellow croaker is more difficult than most people imagine.
It is said that the steps before raising large yellow croaker are extremely complicated, and the pond must be cleaned and disinfected first.
Before stocking the fish, the entire pond should be drained and the bottom of the pond should be exposed to the sun for a period of time to remove excess silt.
15 days before stocking large yellow croaker fry, the pond must be thoroughly disinfected with quicklime. Use water to clean the pond, and use 150 kg of quicklime per acre to make a slurry and spray it throughout the pond.
You can also use tea seed cakes, bleaching powder and other drugs to clean and disinfect the pond.
The drugs used for pond cleaning and disinfection should comply with the relevant provisions of the "Guidelines for the Use of Pollution-Free Food and Fishery Drugs".
The domestication of the feeding habits of large yellow croaker fry is particularly important in the breeding of large yellow croaker.
First of all, bait acclimation should be carried out. The preferred bait is fresh low-value fish and fish paste processed from small coastal fish and shrimp, which should be mixed with eel feed to make compound feed for feeding. Then, gradually increase the amount of fully artificial compound bait and reduce the amount of fish paste until the fish are fed completely with artificial compound feed.
During the bait acclimation stage, workers are required to place feed at fixed points and at fixed times. They also need bait signal training, that is, sending a fixed signal before feeding to allow the fish to form a conditioned reflex and make them accustomed to gathering in groups to feed.
If the domestication is not successful within half a month, these yellow croakers will basically starve to death.
The desalination process of large yellow croaker is not simple, and many fry will die in the process.
Desalination treatment is to gradually add fresh water into the nursery pond to reduce the specific gravity of the pond water and make the seedlings adapt to growing in fresh water.
The gradient change of salinity during desalination has a crucial impact on the survival rate of large yellow croaker. The larger the gradient and the longer the desalination time, the lower the survival rate of large yellow croaker fry.
Generally, it takes 7 to 10 days of desalination. When the salinity of the pond water reaches below 2‰, the seedlings can be placed in the pond for cultivation. This process is very laborious.
And it’s not over yet.
The stocking density should be determined according to the pond conditions and technical level, provided that the stocked seedlings are free of disease, injury, deformity and have strong mobility.
The bait used in the entire breeding process must be marine fish compound feed, and farmers need to feed twice a day.
Before feeding, you need to send a fixed signal to allow the fish to form a conditioned reflex and make them accustomed to gathering in groups to seek food. Feed the bait from a small amount to a large amount, and the "gu gu" sound of the yellow croaker can be heard from the water. When the sound gradually increases from small to large, it proves that the fish have entered the feeding area and are hungry. The sound gradually disappears after the fish is full.
The daily feeding rate is 7-8% of the fish body weight in the early stage and 3-5% of the fish body weight in the middle and late stages.
Feeding must be carried out strictly in accordance with the "Four Determinations" principle, and the amount of feed must be adjusted appropriately based on the situation of remaining bait, combined with weather, water temperature, water quality and fish activity.
In order to increase the survival rate of yellow croaker, farmers also need to regularly add aquatic multivitamins, astragalus polysaccharides, three yellow powder and other drugs to the bait to prevent the occurrence of diseases.
Moreover, the baits that farmed yellow croakers eat are not cheap, and all the baits they eat should comply with the relevant provisions of the "Safety Limits of Pollution-free Food Fishery Feeds". The drugs used should comply with the relevant provisions of the "Guidelines for the Use of Pollution-free Food Fishery Drugs".
Water quality also directly affects the normal growth of yellow croaker. Only by regulating the water quality can we promote the normal growth of yellow croaker, effectively prevent the occurrence of diseases, increase aquaculture output, and achieve the goal of increasing aquaculture production and income.
The water quality for raising large yellow croaker needs to be fresh and not too rich.
In the initial stage of fish stocking, the water level is about 70 to 80 cm. Thereafter, 5 to 10 cm of fresh water will be added to the pond every two days until the highest water level is reached and then the water will be changed.
The water level is relatively low in early spring and late autumn, which is conducive to increasing the water temperature.
In summer and winter, the water level should be raised as much as possible.
The most important thing is that you need to change the water every two days, and the amount of water changed should be 1/4 to 1/3 of the entire pond. For most people, even changing the water is a very troublesome thing.
When the water temperature is below 13℃, basically do not change the water.
When the water temperature is higher than 28℃, it is necessary to change the water every day, with the water change volume being about 1/3. In the hot summer season, drain the water in the afternoon and add water at night. This will stimulate the flow of water, increase the appetite of the yellow croaker, and shape its body shape and color.
These difficulties have always led to the high price of yellow croaker.
As for wild yellow croaker
It has long been listed on the IUCN Red List of Threatened Species.
Large yellow croaker was once an important economic fish species in my country's oceans. Historically, it was listed as one of the four major marine fisheries along with small yellow croaker, hairtail and cuttlefish.
In 1974, the production of yellow croaker was as high as more than 200,000 tons. However, due to the development of boat-knocking fishery in the 1950s, the capture of non-spawning broodstock in the 1960s and 1970s, the over-exploitation of wintering grounds and the capture of juvenile fish, the yellow croaker resources declined rapidly. In 2000, the production in the East China Sea was only 9,035 tons, and no fishing season could be formed in Guanjingyang, Maotouyang and Damuyang.
There is no way around it because the economic value of yellow croaker is so high.
The meat of large yellow croaker is tender and rich in protein, making it a great fresh food. It can not only be sold fresh, canned, and processed into "melon-raised dried fish" and "yellow croaker dried fish", but can also be used in a variety of ways.
The maw of large yellow croaker can be dried and made into various precious foods, such as "fish belly", and can also be made into yellow croaker glue, which is the raw material for high-grade industrial adhesives.
In addition, large yellow croaker has certain medicinal value and is the raw material for some Chinese and Western medicines.
The maw of large yellow croaker can be made into traditional Chinese medicine, which has an immediate effect on treating sinusitis.