What kind of fish is the Nile tilapia? An introduction to its breed characteristics
The Nile tilapia (Oreochromis niloticus), or tilapia for short, is also called the Nile tilapia. It is native to Africa. Taiwan, China introduced it in 1966, and trial farming produced good results; it has now become one of the main species in Taiwan's freshwater aquaculture. In 1978, mainland China introduced this fish successively from Thailand and from the Nile river system. After years of trial farming, the results showed that the Nile tilapia can adapt to the water conditions of most regions of our country, grows well, and has a good yield-increasing effect. At present it has been promoted for farming in more than 20 provinces, municipalities (autonomous regions) across the country. Also introduced at the same time were the Mozambique tilapia (Oreochromis mossambicus), the blue tilapia (O. aureus) and some other tilapias.
The Nile tilapia has a deep, laterally compressed body, and the front of the head is slightly raised. The mouth is large and terminal, with small teeth densely set in the upper and lower jaws. The dorsal fin is quite long; its front section has 16-17 hard spines, and its rear section has 12-13 soft fin rays. The body color is grayish dark, darker on the upper part and paler on the lower part. There is a round black spot at the rear of the dorsal fin. On the sides of the body there are 8-10 faintly visible light black longitudinal bands. The caudal fin has fairly obvious vertical stripes. During the breeding season, the male fish has bright body colors, and its head, back and throat are all red. The lateral line is discontinuous, divided into upper and lower lines; the upper line extends backward from the upper rear edge of the gill cover to the rear end of the base of the dorsal fin; the lower line extends from near the pectoral fin backward along the middle of the body to the caudal peduncle.
The Nile tilapia has a wide diet. At the juvenile stage it mainly eats plankton, and also eats organic debris and small benthic invertebrates. Later, in addition to feeding on plankton, it can also eat the tender leaves and young shoots of various plants. Under pond-farming conditions, it prefers various commercial feeds, green feeds and compound fish baits. This wide-feeding characteristic of the Nile tilapia is very favorable for farming.
The Nile tilapia inhabits the middle and lower layers of the water body, and often goes deep to the bottom to look for food. It has a strong tolerance for low oxygen, and can still grow normally in a water body with a dissolved oxygen content of only 2 mg/L. However, its cold tolerance is very poor, and it is only suited to living in water at 20-35°C. Below 14°C it stops feeding, below 12°C it dies one after another, and above 40°C it is also difficult for it to survive. It has a certain salt tolerance, and can be farmed in seawater with a salinity below 3%.
The breeding habits of the Nile tilapia are very special. It reaches sexual maturity for the first time at only 4-5 months of age. It begins to spawn in mid-to-late May each year, and can spawn 4-6 times a year. During the reproductive period, males and females live in pairs; the male uses its mouth to dig a nest (spawning nest) in the mud and sand, and the female lays eggs in the nest and then immediately holds the eggs in its mouth. The male guarding the side of the fish nest simultaneously releases milt. The eggs are sucked into the female's mouth and fertilized. The fertilized eggs hatch in the female's mouth; when the water temperature is 28-29°C, fry can hatch in about 4 days.
The Nile tilapia grows relatively fast. After about 3 months of rearing, its body weight can reach 0.15-0.25 kg, and it can then be marketed @#@136@#@. Its flesh is good, its food value is great, and it is quite popular among the people.