Freshwater grouper (Cichlaso 138mamanaguense) is a Cichlidae native to Nicaragua, Central America. In Taiwan in 1988, it was a popular freshwater species in southern Taiwan. In 1996, some farming units in Guangdong and Jiangxi were introduced from Taiwan. In recent years, the research on the culture technology of freshwater grouper has attracted the attention of domestic fishery workers. The scale of freshwater grouper is also growing, and it is expected to become a new species of freshwater breeding. The biological characteristics and breeding techniques are now described as follows:
First, the morphological characteristics
The freshwater grouper is a spindle type with an upper mouth. There are eight black lines on each side of the trunk, and darker color blocks are located in the center of the vertical black stripes. Pectoral fins are pale yellow, pelvic fins, dorsal fins, and anal fins all have black stripes and caudal fins with black stripes are perpendicular to the body. In addition to the black and white stripes, the adult fish surface is slightly yellow, and body color adapts to changes in the external water environment and during reproduction. When breeding, males have a darker body color and a lighter female body with yellow, pelvic sternum, round-tailed caudal fins, and a genital process. Juvenile fish eyelids are red, fish eyelids are silvery yellow. The scales are round scales and larger. Side scales are intermittent. Scales are: dorsal fin (D) XVIII-12, anal fin (A) VII-10, pelvic fin (V) I-5, pectoral fin (P) 4.
Second, living habits
Freshwater grouper is a tropical fish that grows in fresh water and can also grow in seawater with a salinity of 10 ‰ or less. The optimum temperature range is between 25-30°C. When the water temperature drops to 20°C, the food intake decreases significantly. When the water temperature drops to 15°C, the body loses its balance. Therefore, the area where the pool water falls below 15°C during the winter is not suitable for breeding. Species of fish. It is better to keep the water temperature above 19°C during the winter. Freshwater grouper is a bottom-level fish that is resistant to hypoxia and has strong resistance to disease. Fish diseases rarely occur during the breeding process. It can be mixed with tilapia and carp to remove small fry in tilapia and carp ponds. The purpose of quality and efficiency.
Three, food
Freshwater grouper is partial carnivorous, and the characteristics of carnivorous stage are very strong. The zooplankton is the main species. Individuals with large disparities will kill each other. Therefore, it is necessary to pay attention to the management of graded ponds when breeding. After the reproduction, the seedlings must be pulled out in time to avoid being swallowed by the broodstock. From the start of fry feeding, artificial diets will be ingested, which can be fed with floating water.
Fourth, growth
The newly hatched larvae of freshwater grouper have a total length of 0.58-0.6 cm. They clustered and kept moving at the bottom of the pool. Between the water temperature of 26-28°C, the yolk sac disappeared on the 6th day after hatching, and the larvae swim to the upper middle water. Layers, no longer clustered at the bottom of the pool, fry after the disappearance of the yolk, can be fed round worms, horns and other small zooplankton, after a little larger can be fed leeches, and then a group of lumps feed bait, after After 1 month of cultivation, the body can be cultivated at a height of about 10 cm. In the Taiwan region, the young fish ponds with a length of about 10 centimeters during the summer period can reach 500 grams after 6-8 months of breeding. Its maximum weight can reach 1200 grams. On June 24, 1999, the famous aquaculture experiment base of our institute introduced a test of about 10 cm in length of fish fry, and it was determined on December 24, 1999. The largest individual was 375 g and the average weight was 216 g; in growth rate, the male fish The growth rate was significantly greater than that of females. In the polyculture mode, the growth rate of less polyculture (20 tails/mu) was significantly greater than the amount of polyculture (150 tails/mu); the average weight of the polycultures was measured. 315 grams, with a large amount of polyculture, averaged 175 grams, a difference of nearly 1 time.
Fifth, reproduction
Freshwater grouper can lay eggs as soon as it is winter. Spawning habits, like tilapia, dig many nests at the bottom of the pond. Spawning is usually in the afternoon, after the spawning females are mainly guarded by fertilized eggs. Males also cooperate with guards, but with the development of embryos, guarding behavior is getting weaker and weaker. Eggs are oval in shape, with a yellow-dark green, opaque, sticky egg and scattered eggs arranged on the bottom of the pool, with little overlap. The females weighing 140 g each lay about 3000-4000 eggs at a time. At a water temperature of 26-29°C, the fertilized eggs can hatch larvae in 48 hours.
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