Among the many aquaculture species in China, golden pomfret can definitely rank among the popular groups of valuable special marine fish. Golden pomfret not only tastes delicious and delicate, its nutritional value is also very high, in China's Guangdong, Guangxi, Fujian and Hainan and other places have a high aquaculture output, by consumers unanimously praised.
So, what kind of fish is the golden pomfret?
The scientific name of the golden pomfret is trachinotus ovatus, and the working people in different regions have given other nicknames according to the appearance characteristics of the golden pomfret, such as red three yellow pomfret, seawater white pomfret, pomfret, etc., but the most widely called is golden pomfret.
Golden pomfret
Golden pomfret is popular in China's southern coastal provinces, it originally came from southeast Asia and southern Africa coastal areas, belongs to the exotic introduction of species. Golden pomfret is a warm water fish, mainly distributed in the middle and upper waters, there is more natural distribution in the South China Sea. If you want to raise a golden pomfret well, you must first start with its biological characteristics.
The golden pomfret is flattened and high on the side, and it has a high degree of recognition in appearance. Soon after the Spring Festival, young golden pomfrets can often be seen swimming in clusters at the mouth of rivers in the southern region, because due to the influence of land-based nutrient imports, the river estuary is the most abundant in nutrients, and the gilt pomfret juvenile fish choose to concentrate on feeding and fattening there. At the adult stage, golden pomfrets concentrate on swimming deep into the open sea, a migration property similar to that of most salmon trout.
In terms of feeding habits, golden pomfret is a typical omnivorous, carnivorous fish, mainly feeding on plankton, crustaceans and small fish and shrimp in the ocean. While most fish are typical opportunists, golden pomfrets tend to show strong feeding agency in natural waters—chasing and preying furiously when they find food. Under artificial culture conditions, golden pomfrets that have been domesticated can also feed on compound feeds of suitable size.
The living water temperature of golden pomfret is 16 to 36 ° C, the most suitable temperature range is 22 ~ 28 ° C, once the sea temperature is lower than 14 ° C, the golden pomfret can not adapt. In contrast, golden pomfrets are more adaptable to salinity, and can survive normally as long as the salinity of seawater is between 3 and 33, but the most suitable salinity ranges from 12 to 23.
Golden pomfret fishing is on the market
As an excellent marine aquaculture species, another advantage of golden pomfret is its fast growth rate: generally as long as it is cultivated for 3 to 4 months, it can reach the marketing specifications of 4-5 pairs, and the breeding can reach 500 to 800 grams a year. Golden pomfret can grow up to 10 kg, but it is not that the larger the size of the golden pomfret is more popular with consumers, considering the cost of feed for farming, the breeding cycle of golden pomfret generally does not exceed two years.
In addition, the golden pomfret is lively and active, belongs to the high oxygen consumption of fish, so the requirements for dissolved oxygen in the water are very high, whether it is pond or cage culture, the dissolved oxygen content in the water can not be less than 5 mg /l. Experimental studies have shown that when dissolved oxygen is 0.91 to 0.99 mg/l, golden pomfret will suffocate to death. As long as the dissolved oxygen is less than 5 mg/l of living for 5 days, the survival of golden pomfret will be reduced to 90% of the original, 50% of the original at 11 days, and at 14 days, the surviving golden pomfret will only be 26% of the initial amount.
There is a special discipline for studying the nutritional needs of fish, namely "Aquatic Animal Nutrition and Feed Science". Although China's aquaculture industry is relatively developed, the research on nutritional needs is relatively backward, basically concentrated in the juvenile fish (weight 10-50 g) stage. At the same time, the quality of the special feed for golden pomfret in the current aquatic market is uneven, mainly because the manufacturer (feed nutrition formulator) does not know much about what nutrients golden pomfret needs to take in at different stages, and more is to make feed formulas according to personal experience.
In recent years, the aquaculture production of golden pomfret in China has been between 100,000 and 150,000 tons, while the demand for feed is 160,000 to 220,000 tons. At present, most feed companies divide the golden pomfret feed into 6 sizes - when the juvenile fish grow to 10 to 15 grams, use the smallest particle size Of No. 0, 15 to 50 grams of the larger No. 1 material, 50 to 100 grams of larger particle size of no. 2 material, and so on, when the golden pomfret grows to more than 300 grams, the unified use of No. 5 material, until the market. The number of feedings per day decreased from 3 to 4 times in the early stage of breeding to 2 to 3 times in the middle and late stages.
However, the configuration of the vast majority of these feeds is not scientific. Studies have shown that each kilogram of golden pomfret feed should contain at least 720 mg of inositol, 49.73 mg of vitamin C, 90 mg of vitamin E, and 42% to 49% protein, 6.5% to 12% fat and 11.2% to 19.8% of sugars. For the study of the demand for other minerals and trace elements in different growth stages of golden pomfret, there is almost a blank space in China.
▲▲ The nutritional needs of a golden pomfret have overwhelmed many domestic and foreign experts
Researchers such as Ou Youjun have tested the activity of digestive enzymes in golden pomfrets at different water temperatures, and the types of digestive enzymes detected in the study are the most common proteases, lipases, and amylases.
The results show that when the water temperature of the cultured water exceeds 25 °C, the protease activity of golden pomfret is higher; when the water temperature is 20~25 °C, the amylase activity is higher; when the water temperature drops below 22 °C, the activity of lipase is higher. It can be inferred that when the water temperature is high, the golden pomfret digests the protein in the feed faster, and when the water temperature is low, the fat in the feed is digested faster.
Therefore, in different seasons, the feed choice of golden pomfret is also different. In the high temperature season, try to choose a feed with a high protein content, not a compound feed with high fat and carbohydrates; in the low temperature season, try to choose a feed with a high fat content, not a feed with a high protein content.
When choosing a feed brand, do not blindly listen to the propaganda of the feed company, and do not covet the discount. The most scientific approach is to try the feed products of 3 companies at the same time, carry out comparative experiments in three small cages, the experimental cycle can be 10 to 30 days, and finally according to the breeding effect of different feeds, with a comprehensive cost performance to decide which type of feed to choose.
The size of each small cage can be set to 1×1×2 meters, and 40 golden pomfrets can be placed in each cage, and the test cost is not too high. Through the comparison experiment of small cost, the information obtained by farmers is very valuable: in the subsequent breeding process, not only can the cost of feed be saved, but also the best breeding effect can be achieved, and the farmer also saves the trouble of choosing feed back and forth.
▲▲In a large cage, it can be divided into 3 small boxes with purse seines to facilitate the comparison experiment
1. Selection of aquaculture sea area
Cages used for the cultivation of golden pomfret are best set up in areas with smooth water flow, small airflow and a flow rate of 15 to 20 cm/s. The bottom of the cage is about 1.5 meters away from the seabed, and it is best to choose a place with convenient maritime transportation and a relatively stable water quality environment.
Studies have shown that the flow rate of seawater can have a significant impact on the average daily weight gain of golden pomfrets. The researchers set up two sets of experiments A and B, when stocking, the weight of the gilt pomfret juveniles is between 2 and 5g, the number of farming days is 30 days, the only difference is the water flow rate of the cultured waters. The flow velocity of group A was 5~15cm/s, and the flow velocity of group B was 10~25cm/s, and it was found that after 30 days of breeding, the golden pomfret in group A grew to 26~35g, while the weight of golden pomfret in group B was 24~30g, which was generally smaller than that of golden pomfret in group A (with a smaller flow rate).
There are two main reasons for this result: one is that the larger water flow speed will wash away the feed thrown into the water, and part of the feed has not been washed away by the golden pomfret, so the total feeding amount will be significantly lower; on the other hand, the water flow rate is larger, and the gilt pomfret juvenile fish need to consume more energy to overcome the impact of the water flow, disguised to increase the amount of movement of the juvenile fish, which has played a certain "weight loss" effect.
2. Optimal density for cage culture
Regarding the optimal culture density of golden pomfret, relevant tests have also been carried out in production. The experiment set up four culture density gradients, 27, 35, 44 and 50 golden pomfrets were cultured in each cubic body of water, and the size of the stocking was 25 grams. After the end of the experiment, the average weight of the golden pomfret obtained at these four densities was 600 g, 540 g, 510 g and 480 g, respectively. Not only that, the group with the lowest density (only 27 fish in 1 cubic water body) also obtained the largest survival rate, as high as 90.08%, while the group with the highest density (50 fish in 1 cubic water body) had a survival rate of only 79.36%.
▲▲Experimental data and breeding examples
From the perspective of comprehensive breeding benefits, a reduction in the breeding density of golden pomfret by 20 to 30% can greatly increase the growth space of fish, the growth rate will be significantly accelerated, and the comprehensive breeding benefits will be higher. Therefore, it is recommended that when leaving the pond, it is advisable to control the breeding of 18 to 22 golden pomfrets in each cubic water body, and the size of the pond is 500g/tail.
3. Optimal number of feedings: Speak with experiments
In 2006, Researchers such as Hu Shiliu explored the relationship between the number of feedings and the effect of golden pomfret farming. The initial weight of golden pomfrets is controlled at 130 to 150 grams during stocking, and the weight of each feed is 30 grams, and the number of feedings is from 1 to 6 times a day, for a total of 6 groups.
The results showed that the average daily weight gain of a group fed 6 times a day was 0.86 to 0.92 g, the average daily weight gain of 5 times was 0.82 to 0.90 g, and the average daily weight gain of 4 times was 0.80 to 0.87 g. Among all the groups, the average daily weight gain was only 0.10 to 0.13 g, and the group was fed only once a day.
It should also be pointed out that the average weight gain of golden pomfret fed 4 times a day is 0.3 to 1.0 grams per day, although its upper limit of 1.0g is the highest among all groups, but its lower limit of 0.3g is not dominant, and the size of the golden pomfret in this group varies in size and is poor in neatness.
From the experimental results, it can be seen that in the breeding and production, a small number of investment methods are used as much as possible, and the number of feedings per day can be controlled at 4 to 5 times, which can not only guarantee the rapid growth of pomfret, but also maintain a good uniformity. In addition, it is also necessary to flexibly adjust the feeding amount and feeding frequency according to the climate and water quality conditions of the day, generally rainy weather less feeding or no feeding, high temperature and sunny days as much as possible, the daily feeding volume accounts for 8% to 10% of the fish's body weight.
4. How to determine the feeding time? Mainly refer to the water temperature situation
The high sea temperature from July to September of each year is the rapid growth period of golden pomfret, and the golden pomfret feeds rapidly at this stage, but it is also prone to enteritis and other diseases.
▲▲The amount of feeding of golden pomfret in the high temperature season will increase, and the burden on the digestive system will also increase, and diseases such as bacterial enteritis will have an opportunity
In order to avoid high temperature stress in golden pomfret, some immune enhancers can be added to the feed. In terms of feeding time, juveniles are generally fed 3 meals a day, which are 5-6 am in the morning, 7 pm and 12 am in the morning. When the golden pomfret grows to medium size, the number of feedings is reduced to 2 meals per day, 1 a.m. and 8 p.m. (the time is determined according to the water temperature).
Extreme convective weather such as heavy rain and typhoons often occur along the southern coast, especially heavy rain, which will significantly reduce the salinity of surface seawater, which has a great impact on cage cultured golden pomfret. Studies have shown that at low salinity, the activity of protease, lipase and amylase in gilt pomfret fish is significantly reduced, and the decrease in lipase activity is greatest. Therefore, in aquaculture production, it is not advisable to feed bait during continuous rainstorms, let alone feed with high fat content, otherwise it will greatly increase the burden on the digestive system of golden pomfret.
Cage culture of golden pomfret is very common in the southern coastal provinces, with good farming prospects and economic benefits. In addition to doing a good job in the above breeding work, breeding personnel should also observe, detect, prevent diseases diligently, and do a good job of anti-theft inspection work - this is not sensational.
On March 22, 2020, a case of stealing golden pomfret occurred in Xuwen, Zhanjiang, and more than 50% of the 40,000 kilograms of golden pomfret that farmers worked hard to breed were stolen, and the market price was about 17.5 yuan / catty at that time, and the direct economic loss was as much as more than 300,000 yuan. "Sometimes it is not necessarily competitors who eliminate people", and it is necessary for farmers to strengthen night patrols at sea to prevent theft from happening again.
▲▲Harvesting process of golden pomfret: first use a trawl to concentrate the golden pomfret in a small area, increase the density, and then use the hanging net to quickly transfer.
Finally, I hope that golden pomfret farmers can obtain high yields and high efficiency, and consumers can also eat fresher, healthier and high-quality golden pomfret!
What do you think about the scientific farming of golden pomfret? Feel free to leave a message in the comments section to discuss! #Aquaculture# #Golden Pomfret # #Sannong ##Cage Farming #### Find the Most Beautiful Workers# #