Balanced aerobic cage is a kind of flowing water culture, but the water flow of most reservoirs and rivers is not large, especially in high temperature period, feed residue and feces continue to ferment at the bottom of cage, and the ammonia nitrogen and nitrite produced affect the absorption and utilization of oxygen by grass carp. In this way, the grass carp in the cage will also float at night. The author visited many cages and detected dissolved oxygen. The results showed that the dissolved oxygen in cages was 4.0~5.5 at noon on sunny days and 2.5~3.5 at night, indicating that there was still room for improvement in cage grass carp culture. Dissolved oxygen level is the key index of catch. At present, most cage grass carp farmers have not installed aerators. The author suggested that some farmers install microporous aerators, which achieved good results, fast growth, healthy fish, reduced the feed-to-weight ratio and effectively reduced the breeding cost.
Feeding management is the key link of grass carp breeding, which requires diligent and careful farmers and is the main factor to determine the survival rate and cost of breeding. The selection of seeds and the control of feeding speed will be discussed below.
Uniform packaging
After the fish is 300~500g thick, the farmers begin to box and enter the stage of adult fish culture, and attention should be paid to the selection of specifications during the process of boxing. Grass carp of the same size are concentrated in the same cage. Grass carp don't eat like carnivorous fish, so it is easy to be ignored by farmers. Box screening has two advantages. On the one hand, the uneven size often leads to the small fish can not get close to the feeding platform, and the feeding is not smooth, resulting in a low overall feeding rate. The growth time of small fish is prolonged, so it is difficult for farmers to grasp the high-priced market; On the other hand, it is convenient to calculate the weight of cage fish by evenly dividing boxes, and the feeding rate can be calculated according to the weight, which is convenient for fine feeding management. Pay attention to the use of anesthetics in the screening process to avoid hurting fish.
Feeding speed is suitable for "time"
In the cage culture of grass carp in Fujian Province, the fingerlings are usually put in and sold. It is advisable to use high-protein feed, mixed with vitamins, vitamin C and other health care drugs to improve physical fitness and anti-stress ability. The water temperature began to rise above 25℃, and the water temperature was more suitable. At this time, the fingerling is below 500g, which is the physiological stage of the rapid growth of grass carp. It is suggested that grass carp should be fed with enough bait, and the feeding rate should be above 3%. According to the weather and body shape, choose 1 ~ 2 days a week, and properly control feeding. When the water temperature is above 30℃ and the fish weight is above 500g, it is in a slow growth period, the water temperature is slightly higher and the dissolved oxygen is poor. Therefore, the feeding amount should be properly controlled, and the recommended feeding rate is about 1.5%~2%. Avoid the occurrence of hepatobiliary syndrome caused by overfeeding. After September, the water temperature is about 28℃ and the size of grass carp is about 1 1,000 g. It is suggested to use high-grade feed to ensure the feeding rate of about 3%, and it is necessary to observe the body shape and control the feeding at the weather selection stage.
There are many articles about aquaculture management to improve aquaculture efficiency, so I won't go into them one by one. If the food is abnormal, we should not only pay attention to the weather changes, but also observe the swimming state of grass carp and prevent parasites and bacteria in time according to different seasons. It is more important to establish an effective detection and prevention mechanism for grass carp viscera, especially liver and intestine.