Introduction to Red Tilapia and Detailed Explanation of Farming Techniques

I. Biological Characteristics of Red Tilapia:
1. Brief Overview of Introduction, Selective Breeding and Farming:
In fish taxonomy, red tilapia belongs to the order Perciformes, suborder Percoidei, family Cichlidae, genus Tilapia, and is a tropical fish. According to documented sources, red tilapia was originally introduced from Israel by Taiwan, China in 1965, and drew attention in Taiwan in 1968, with farming scale continuously expanding. In October 1973, a delegation on aquaculture to Japan organized by the former Ministry of Agriculture and Forestry and the Ministry of Foreign Trade received a gift from an overseas Chinese in Japan and brought back 229 fry, introducing the fish to the Chinese mainland. Because this batch of fry showed great segregation in offspring and their growth rate declined year by year, their promotion value decreased and they were eliminated. In 1981, the Pearl River Fisheries Research Institute reintroduced 110 red tilapia fry of 3 cm from Taiwan via Hong Kong, China, of which 72 survived. This was an earlier introduced strain.
Afterwards, through multiple channels, the scale of introduction and farming continued to expand, enabling red tilapia output to increase fairly rapidly in the south, especially in Fujian, Guangdong, Guangxi, Hainan, as well as Hubei, Yunnan, Jiangsu and other provinces, municipalities and autonomous regions. Relevant research institutes in Guangdong, Fujian and other provinces had already carried out selective breeding of improved red tilapia varieties before 1990, achieving very good results. For example, the Foshan Fisheries Research Institute of Guangdong Province, starting in 1986 and using four years, took determining the genetic characteristics of red tilapia as the breeding basis, used body color, body shape and growth as indicators, and adopted a method comparing individual selection with mass selection to conduct breeding research on red tilapia introduced from Taiwan, China; the obtained F5 and F6 generations had obvious superior traits. The proportion of red individuals was 75.8% and 80% respectively, and growth rate increased by 10.87%-16.73% and 12.4% respectively. Population yield increased by 13.72%-25.54% and 25.2% respectively. Under conventional farming, yield per mu was above 300 kg.
In recent years, small cage farming has developed. In some areas of coastal provinces such as Fujian, the main farmed species is red tilapia. In 1998, Zhuanji Town, Jieshou City of our province conducted a trial: in a river channel with an area of about 100 mu and a depth of 4-5 m, 3 cages each 6 m long, 5 m wide and 1 m deep were set up, with a total area of 90 sq m. On July 8, 7,000 summer fry of red tilapia measuring 3-5 cm were purchased from Fujian and fed eel pelleted feed twice a day. After more than three months of rearing, the average body length was 25 cm, body weight was 280 g, survival rate was 85.7%, and total fresh fish output was 1,680 kg. After deducting the cost of fingerlings, freight and feed, the profit was tens of thousands of yuan.
　　
2. Biological Characteristics:
Based on biochemical genetic and cytological analyses, red tilapia may be a hybrid variant of Mozambique tilapia and Nile tilapia; its genetic relationship is close to Nile tilapia, and its body shape resembles Nile tilapia. Its body color is mainly red and yellow, bright and very attractive, with both food and ornamental value. Because its body shape resembles the marine fish red seabream and its flesh is delicious, it is also called "rainbow seabream". The body of red tilapia is laterally compressed; body length is 3-3.1 times head length and 2.4-2.5 times body height. The mouth is small, and the mouth cleft does not reach the eye margin. The dorsal fin has 16 spines and 12-13 soft rays; the lateral line is divided into upper and lower sections, with 29-30 scales along the lateral line.
　　
3. Living Habits:
Red tilapia can tolerate water temperatures of 8-42°C, with a suitable water temperature of 24-30°C. It can survive under relatively low dissolved oxygen conditions. In pond farming it readily shows gasping at the surface, but generally does not die in large numbers. Under the same conditions, pond stocking density can be 2-3 times higher than that of ordinary high-quality fish species. It also has strong adaptability to salinity and, after gradual acclimation, can be farmed in seawater.
The natural food of red tilapia is zooplankton and phytoplankton. Young fish feed on zooplankton and also eat some green algal phytoplankton; after growing larger, they mainly feed on phytoplankton and organic detritus in the pond. Under artificial farming conditions, they can eat fish meal, trash fish, silkworm pupae, soybean cake, rice bran, wheat bran, vegetable leaves and various animal feeds. This fish has a large food intake and strong digestion and absorption capacity.
After 4 months of pond rearing, fry of red tilapia produced in the same year can reach more than 150 g if managed properly, and can reach about 500 g before overwintering.
Red tilapia reaches sexual maturity in the same year, and some can spawn after 150 days of rearing. When the water temperature is above 20°C, mature male fish begin nest-digging reproductive activity. Fertilized eggs are incubated in the female's mouth until the larvae are capable of activity. During the breeding period, female fish do not feed, from which it can be seen that growth differences will appear between male and female fish. If artificial propagation is carried out, young fish should be separated and reared in time to avoid being swallowed by parent fish. After young fish grow slightly larger, if density is too high, mutual cannibalism can also easily occur.
Like several other tilapia species currently being promoted for farming, red tilapia is a variety with few diseases, easy rearing and fast growth.
　　
II. Farming of Red Tilapia
1. Pond Farming
① Pond conditions: Like other tilapia, red tilapia does not have high requirements for ponds. Generally, ponds below 5 mu are better, mainly for ease of management and harvesting. Pond depth is 2 m, and water depth is about 1.5-1.8 m. Water quality should be good, and water can be exchanged and added. Before stocking fry and fingerlings, the pond must be cleared and disinfected, and fertilized to cultivate water quality.
② Fingerling stocking: According to the requirement of a total yield of 500-600 kg per mu, for main culture, 3,000-4,000 summer fry can be stocked per mu, or 1,500-1,800 overwintering fingerlings of 10-20 g. In the former case, autumn body weight can reach 150-200 g; in the latter case, it should be about 400 g, so stocking larger fingerlings is better. In addition, 200-300 fingerlings of carp, crucian carp, silver carp and bighead carp can be stocked. For mixed culture density, with the "four major Chinese carps" as the main species, 200-500 overwintering red tilapia fingerlings of 5-50 g can be mixed in. Autumn harvest size is 250-500 g. Fingerling stocking should be carried out when water temperature is stable above 18°C.
③ Feeding management: In the early rearing period, the fingerlings are small and like to swim in groups to feed, so attention should be paid to properly feeding high-nutrition fine feed to promote rapid growth of fingerlings. In high-temperature seasons, because fish density is relatively high and more feed and fertilizer are applied, gasping at the surface easily occurs, so water should be changed frequently and new water added; if an aerator is available, it should be turned on in good time for aeration. In the later rearing period, that is, August-September, some fish have reached market size and should be harvested in time. First, this can take advantage of the off-season for fishing to enter the market and raise the selling price; second, it can reduce pond fish density, manage the later period well, and improve size.
2. Cage Farming
① Conditions for setting up water areas: Generally, small lakes, reservoirs, river channels and ponds with fresh water quality, open water surface, water depth above 2 m and no pollution can all be used for cage installation, and places with slight water flow are best. The cage bottom is required to be 30-50 cm from the water bottom.
② Cage specifications and installation: Cages for farming red tilapia should be somewhat smaller, mostly 10-30 sq m. It is best to develop small cages of 1-4 cubic meters for farming red tilapia, as both installation and management are convenient. A spacing of 3-5 m should be left between two cages; cages should be arranged perpendicular to the direction of water flow, and there should also be a distance of more than 10 m between two rows.
③ Stocking density and size: Traditional cages are generally several tens of square meters, with several tens of fingerlings stocked per square meter. In the small cages promoted in recent years, according to different water area conditions and management levels, 200-600 fingerlings can be stocked per cubic meter. Larger fingerling size is better; small cages require fingerling size of about 50 g each, and the October market size is 400-500 g.
④ Feeding management: In water areas with clear, lean water and high transparency, cage farming mainly uses pelleted feed. The feed must be nutritionally complete, with a protein content of 28%-32% and crude fat of about 5%; in addition, certain vitamins and minerals must be added. Feed 2-3 times a day; according to different water temperatures and different developmental stages of the fish, the daily feeding amount is 2%-5% of fish body weight.