How to farm freshwater grouper? Detailed high-yield farming techniques
Freshwater grouper is a tropical fish native to Nicaragua in Central America. It was introduced to Taiwan, China in 1988 and is a common freshwater aquaculture species in southern Taiwan, China. In 1996, aquaculture units in Guangdong and Jiangxi introduced it from Taiwan, China. It features fast growth, tolerance to low oxygen, and strong disease resistance. Let us take a look at the high-yield farming techniques for freshwater grouper below!
Living habits
Freshwater grouper can grow in freshwater and also in seawater with a salinity below 10‰. Its suitable temperature range is 25-30°C. When the water temperature drops to 20°C, feeding decreases noticeably; when the water temperature drops to 15°C, the body loses balance. Therefore, areas where pond water drops below 15°C in winter are not suitable for farming. During the overwintering period, freshwater grouper grows at a water temperature above 19°C. It is a fish with carnivorous tendencies, and the carnivorous characteristic is strong at the fry stage, mainly feeding on zooplankton.
Reproductive habits
Freshwater grouper can spawn at one winter of age. Its spawning habit is the same as that of tilapia, digging many spawning nests at the bottom of the pond. Spawning generally takes place in the afternoon. After spawning, the female fish mainly guards the fertilized eggs, and the male fish also guards cooperatively, but as the embryo develops, the guarding behavior becomes weaker and weaker. The eggs are oval, yellow-dark green in color, opaque, adhesive eggs, scattered on the pond bottom, rarely overlapping. A female fish weighing 140 grams lays about 3000-4000 eggs each time. At a water temperature of 26-29°C, the fertilized eggs can hatch into fry after 48 hours.
Fry and fingerling rearing
1. Disinfection and stocking: It is best to use earthen ponds for freshwater grouper fry and fingerling rearing ponds. Use quicklime to clear and disinfect the pond and fertilize the water quality. Before stocking fry, test the water first. The specifications of fry stocked in the same pond should be consistent, and the density depends on feed, farming technology level, and rearing specifications.
2. Water quality management: Freshwater grouper fry rearing easily deteriorates water quality. Water should be changed once every 3-5 days, with 1/4 of the water changed each time. Aquatic plants can be transplanted in the pond to purify water quality and provide hiding and feeding places for fry. When there are large differences in fry specifications, they should be screened and raised separately.
Feed feeding
1. Feeding of newly hatched fry: Freshwater grouper has carnivorous tendencies. When newly hatched fry are put into the pond, they feed on zooplankton. As the fry grow, their food intake increases, while zooplankton in the pond gradually decreases. Zooplankton can be cultivated by topdressing fertilizer, and soybean milk can be added as feed.
2. Food training of newly hatched fry: When freshwater grouper newly hatched fry reach more than 3 cm, food training can be carried out. First feed minced fish on the feeding platform. After 2-3 days, add a small amount of compound feed mixed with minced fish, then gradually increase the compound feed until all compound feed is used.
3. Feeding management: The daily feeding amount of freshwater grouper is about 20% of fish body weight. The protein content of compound feed should be 35-40%, animal protein should be more than 25%, and other plant protein raw materials can be added. The feed conversion ratio can reach 0.8-1.2.
Adult fish farming
1. Small-scale polyculture: Freshwater grouper can be polycultured in small amounts in ponds, with about 25-50 freshwater grouper per mu of water surface. After half a year of farming, the average body weight can reach more than 300 grams; after one year of farming, the body weight can reach about 500 grams.
2. Pond main culture: Freshwater grouper can be polycultured with tilapia, grass carp, crucian carp, etc., with 150-200 fish per mu of water surface and 300 polycultured fish. After half a year of farming, the average body weight can reach about 200 grams; after one year of farming, the body weight can reach more than 250 grams.
Disease prevention and control
1. Tail rot disease
[Harm] The fin base of diseased fish is congested, most seriously in the caudal fin, pelvic fin, and pectoral fin. Body color fades, and local redness, swelling, and ulcers appear on the sides of the body. In severe cases, the mortality rate can be as high as 90%.
[Prevention and control] Soak and wash with tetracycline or oxytetracycline for 4-10 minutes each time, for 2-3 consecutive times, or splash furazolidone over the whole pond once a day for 3 consecutive days.
2. Gill rot disease
[Harm] The gills of diseased fish are pale red, the ends of gill filaments are congested, and local gill tissue necrotizes and turns white. In severe cases, the tissue rots and cartilage is exposed.
[Prevention and control] Splash sodium dichloroisocyanurate over the whole pond. For prevention, use 15-20 kg of quicklime per mu at a water depth of 1 m and splash it over the whole pond.
3. White spot disease
[Harm] Irregular white spots appear on the body surface of diseased fish. In severe cases, the white spots merge into patches. Mucus on the fish body surface and gills increases, swimming becomes slow, breathing is difficult, and the fish often float on the water surface.
[Prevention and control] Soaking diseased fish in freshwater for 2-4 minutes can kill the pathogen, or soak diseased fish in copper sulfate for 2 hours, for 2-3 consecutive days.
4. Vibriosis
[Harm] The body color of diseased fish fades, and local redness, swelling, and ulcers appear on the body surface. It mostly occurs from April to November, most seriously from April to June, and the mortality rate can reach more than 90%.
[Prevention and control] Soak and wash with antibacterial drugs such as nitrofurazone for 3-5 minutes, or orally administer Fish and Shrimp Zhuangyuan mixed into feed at 3-5% and feed for 5-7 days.