The spotted totoaba is also known as the American redfish. It is an excellent breed introduced to China by the First Institute of Oceanography of the State Oceanic Administration in recent years and successfully bred, and is a warm water fish with wide temperature and wide salt offshore. This fish is tender and delicious, and has great medicinal value. Set of fast growth, strong disease resistance, a wide range of aquaculture feed and other advantages, is currently emerging another popular marine aquaculture species.
First, the choice of water environment
(1) The breeding area should exclude the infiltration of any sewage and impurities. Nets are opened in the shallow water nearby to facilitate the acquisition of fresh small trash fish and shrimp bait. Sheltered from positive winds or typhoons is advisable.
(2) The stocking pond selects the bottom material without "blackening" and pollution, has the ability to enter and drain, and the water quality is fresh. The minimum water level ranges from 1.2 to 1.5 meters, and it is advisable to use 2 to 3 meters.
(3) Water temperature range: 18 ~ 33 °C, with 25 ~ 30 °C growing fastest. This is especially noticeable after a body length of 15 cm.
(4) Salinity range: 2% to 3%, can also be domesticated in brackish water.
(5) Dissolved oxygen: its critical concentration of death is 2.2 mg/L, and generally more than 4 mg/L can be grown normally.
(6) pH: pH 8.2~8.5 is the most suitable for the growth of redfish.
Second, the cage specifications and settings
From local practice, redfish cages can be determined according to the number of rearings. Generally, fry cages of more than 3 cm are raised in 2 m X 2.5 m. It is more common to raise large seedlings over 15 cm in cages with a × of 3 m X 3 m. Those who have the conditions can design their own fish steaks in the selected sea area. The cage depth is 1.5 to 3 meters. Depending on the minimum water level, the bottom of the net should not touch the ground.
The cage layout should be parallel to the inlet and drainage flow direction, so that the water in the cage flows, ensuring the supply of dissolved oxygen and the elimination of metabolites.
3. Breeding management
(1) Fry selection and transportation: pay attention to the main features, that is, there is a black spot above the base of the fish tail stalk, the adult body color is reddish, and the fry is not obvious. It is required to choose a body length, strong vitality, no disability, no illness and weakness. Large head, broken skin, broken tail, etc. should not be used. Sizes should be more than 3 cm. Special oxygenated water bags must be spared for transportation. The volume of transport must be determined in conjunction with the delivery time, and the water temperature of the fry transported must first be reduced to below 21°C.
(2) Stocking time and method: The stocking time of the northern coast is appropriate in early to mid-June, and the water temperature is above 18 to 20 °C. The salinity ranges from 2.6% to 3%. Fry should not be transported directly into the box after being transported to their destination. Fry bags should be placed obliquely in the stocking pond for more than 1 hour before pedestrian boxes to avoid stress reactions so that the fry can adapt to the new water. Before the human box, 0.2 to 0.3 ppm potassium permanganate can be used for a medicinal bath for 1 to 3 minutes to prevent disease growth.
(3) Stocking density and classification: Stocking density must be reasonably allocated according to the number of cages. Fry over 3 cm should be × 2 m × 2.5 m cages, and 200 fish/carton. Seedlings above 15 cm should be 3 m × 3 m× 3 m cage, 300 fish / box is appropriate. After the fry is purchased, it must be carefully classified and cared for according to the size of the fish, disability, thinness, etc.
(4) Bait volume and method: Bait varieties: mainly fresh small trash fish, shrimp, sand silkworms, shellfish meat, with a small amount of shrimp compound feed (crude protein content of more than 40%). Feeding method: first throw into the middle of the cage, so that the fish can quickly feed until saturation sinks, and then a small amount is thrown around to facilitate the feeding of weak and small fry and promote the uniform growth of fry. Baiting time: It is best to throw bait in the morning and afternoon when the light is weak, the water temperature is low, and the water surface is calmer, and it is advisable to throw bait twice a day. Bait control: The principle is to flexibly grasp the appetite of fry. It is advisable to take 8% of the daily bait of the fish's body weight, and the bait coefficient is controlled below 7.
(5) Growth detection and disease prevention: As the growth trend of fry accelerates, a corresponding amount of cages should be prepared. Inverted bin cleaning: clean the cage regularly every 10 days or half a month, and then disinfect it by daylight for 2 to 3 days. And strictly check whether the cage is damaged to prevent leakage. Growth testing: Every half month or 20 days to detect or sample the growth rate of redfish, whether there is morbidity, residual bait, or residual food. According to the physical and chemical factor monitoring data, to determine the implementation of technical means such as water quality update, adjustment of bait volume, and prevention and control of diseases.