Article from: Bring Science Home, Author: Seven Jun.
Let's take a look at the important protein source of human beings, and their adaptability and fertility are comparable to those of small and strong tilapia-
This is its essence—
Usually we talk about tilapia, mainly including oreochromis in the lid family, Sarotherodon and non-crucian carp (tilapia).
Tilapia is the second largest commercial fish in the world (the largest is carp). Ancient Egypt began farming tilapia 4,000 years ago, but the globalization of tilapia began in the 1940s and 1950s.
In 2018, global tilapia production reached 6.3 million tonnes, equivalent to the weight of 100 million adults combined. 120 countries around the world are involved in the cultivation of tilapia, of which the largest production is china.
Our tilapia was introduced in 1978. From 1992 to 2003, more than half of the world's tilapia was farmed in our country. According to the 2017 China Fishery Statistics Yearbook, China's tilapia production in 2016 was 1.8 million tonnes.
Sauerkraut fish made with tilapia
The main importer of tilapia is the United States. In the United States, tilapia is the fourth most consumed fish, and almost all mid- and low-end restaurant chains sell tilapia. Because the price is civilian, the fish bones are less meaty and tender, the raw materials for grilled fish, "snapper" sashimi and sauerkraut fish in many domestic restaurants are also tilapia.
Tilapia fillets sold on an e-commerce platform
You may not know how strong tilapia are, and they can adapt to a variety of pit daddy environments. For example, in salton sea, a large salt lake that is known not to even survive marine fish, tilapia can grow happily.
Tilapia nests exposed after the Salton Sea in California dried up
Tilapia can also adapt to water temperatures spanning up to 30 degrees Celsius. Take, for example, the most common tilapia, oreochromis niloticus, which can live in hot springs from 11 degrees Celsius to 42 degrees Celsius.
The most common tilapia, oreochromis niloticus Image source: wikipedia
And tilapia eats everything, from plankton to debris to membranes.
You're right, because tilapia is not a picky eater, many developing countries often use tilapia when farming tilapia. According to the Food and Agriculture Organization of the United Nations (FAO), when tilapia is farmed, people often feed animal manure and agricultural waste (such as bran) in fish ponds. Tilapia can spawn plankton, tilapia super love to eat, with "poop" meat, killing two birds with one stone, no wonder tilapia is called "protein source that does not need protein".
Tilapia cuisine
Animals that are highly adaptable are usually also very capable of reproduction, and tilapia is no exception. Tilapia are fish that will not stop breeding as long as there is an opportunity, and can be called a rat in the water.
But tilapia is not the kind of animal that runs when it is born, they are very responsible parents, and the children are hatched in the mouths of their parents/ mothers.
Tilapia is harvested on farms in the Philippines
For example, after the eggs of the Nile tilapia are fertilized, the mother tilapia will immediately hide the children in their mouths to hatch, and the Sarotherodon melanotheron (Sarotherodon melanotheron) is responsible for the baby.
This picture is not suitable for children who are afraid, when everyone makes up for eating fish, the yellow fish roe is not dug out of the belly of the fish, but out of the mouth of the fish. After the fry hatches, they will return to their parents' mouths when they encounter danger.
Tilapia farms in the Philippines release fry in fish ponds
However, because tilapia is so good at life, humans can't control it. If the farm is matched by male and female, then the tilapia children will brush the owner of the fish farm, and the small fish will be thin and have no meat because they compete for food. Coupled with the fact that males grow twice as fast as females, tilapia farms in various countries have been using hormonal sex-reversal techniques to turn tilapia sisters into younger brothers since the 1970s.
clams? Can tilapia still be denatured?
Yes, although the sex of the tilapia gene is fixed at the time of fertilization, the sex of their bodies is variable for a few days after hatching, because their sex differentiation occurs after incubation. If the female (genotype XX) is allowed to eat the male hormone 17α-methyltestosterone during this period, which is the type of drug that athletes take to enhance their physical fitness, then the tilapia girl will become a girl whose body is a boy but whose genes are girl.
Of course, because of the problem of androgen drug residues, many consumers feel very unhappy, after all, not everyone wants to become brothers after eating sauerkraut fish. Now many fish farms have begun to change their thinking, using hybridization (cross-species hybrid tilapia is male), or using super-male (male fish with genotype YY) and other means to produce pure tilapia.
Because tilapia thieves can grow, degenerate, are not picky eaters, and are resistant to disease, in addition to eating them, many places use them as garbage trucks to clean up river ponds and suppress mosquitoes, and then they naturally become invasive species.
However, such a powerful fish also encountered mysterious opponents.
About 10 years ago, Israeli tilapia began to die mysteriously in large numbers. These tilapia have festering skin, bleeding from their internal organs, and infected tilapia look a bit like a carp king after being beaten violently.
In 2014, researchers finally found the culprit of this mysterious infectious disease, which turned out to be a virus, and later it was named Luohu virus (TiLV), and the disease caused by this virus was called Luohu disease.
Luohu virus is a completely new RNA virus that is not related to other known viruses except for its weak association with influenza C virus.
On 14 June 2017, the Asia-Pacific Network of Aquaculture Centres (NACA) warned of the possible spread of tilapia outbreaks around the world.
Luohu disease is extremely infectious, can KO common commercial tilapia species and some wild tilapia (Luohu disease does not infect humans), morbidity and mortality rate of up to 90%, and no medicine and no vaccine. What is even more frightening is that about 5 years ago, the Luohu virus began to spread in tilapia farms around the world. Outbreaks of Luohu disease have occurred in Asia, Africa and the Americas, where tilapia is the main culture area, including in Israel, Ecuador, Mexico, Thailand, Indonesia, India, the Philippines, Malaysia and Taiwan.
This month, John Benzie, a geneticist at the International Nonprofit WorldFish Center, said in an interview with Science: "This is already a serious global problem. ”
As the largest producer of tilapia, has China's tilapia been recruited?
China's tilapia farms are mainly distributed in Guangdong, Hainan and Guangxi. Although China has not reported the outbreak of Luohu disease to the World Organisation for Animal Health (OIE), Matthew Stone, vice president of the OIE, said in 2019: "The world is highly vigilant against Luohu disease, and China should also be vigilant." ”
In 2018, the Food and Agriculture Organization of the United Nations released a Tilapia LAKE VIRUS Expert Knowledge elicitation risk assessment, which called China's risk "high" and recommended that China limit imports of tilapia to protect its industry.
The report also notes that because live tilapia is a frequently traded commodity, Lo wu disease may have unwittingly spread widely.
Hopefully, the day when both humans and steel straight male sauerkraut fish will come out of the epidemic and reunite in restaurants!