Editor's note:
The protection of biodiversity and the protection of ecological security have attracted much attention from the international community today, among which the invasion of alien species is one of the hot spots. Internationally, invasive alien species are listed as the second most important contributor to biodiversity loss, after habitat destruction. The report of the 20th National Congress of the Communist Party of China emphasized "the implementation of major projects for biodiversity conservation ... to prevent and control the infringement of alien species". In 2023, Central Document No. 1 proposed to "severely crack down on the illegal introduction of alien species, implement major prevention and control actions against invasive species, and strengthen the standardized management of the trade and release of 'exotic pets'." "The prevention and control of invasive alien species is related to food security, biosecurity and ecological security. In recent years, with the increasing frequency of commodity trade and personnel exchanges, the spread of invasive alien species is faster and the invasion routes are diversified, the continent is vast, both land and sea, and the landform and climate are complex and diverse, so most invasive species can find a suitable living environment on the mainland, once harmful alien organisms enter and colonize (long-term survival state), it is very difficult to completely eradicate, which will seriously affect the ecological environment of the invasion area, damage the sustainable development of agriculture, forestry, animal husbandry and fishery and the stability of the ecosystem.
What are the common alien aquatic species around us? What harm do these alien aquatic species cause? How can we prevent the invasion of alien species? Popular Science China Zhihui Farmers launched a series of popular science articles on "Prevention and Control of Invasion of Aquatic Alien Species", welcome to pay attention.
Today our protagonist is the familiar exotic fish - tilapia.
Mozambican tilapia Oreochromis mossambicus| Greg Hume
What kind of fish is tilapia?
Tilapia, native mainly in Africa, is called "African crucian carp" because of its similarity to crucian carp, although tilapia is similar in size to crucian carp, and its diet is omnivorous like crucian carp, but they are not crucian carp. Because tilapia belongs to the fish of the order Perciformes and the family of cichlids, and crucian carp belongs to the fish of the order Cyprinidae and the family Carpidae, the relationship between tilapia and crucian carp is like the kinship of pigs (mammals, cetaceans, pigs) and dogs (mammals, carnivores, canines), so African crucian carp (tilapia) is not crucian carp. In addition to this common name, it has other names such as Ku Guo Fish, South Sea crucian carp, Vietnamese fish, etc. It is called Wu Guo fish because tilapia was first introduced to Taiwan Province in 1946 by Wu Genhui and Guo Qizhang, and then the mainland mainland introduced tilapia from Vietnam, Thailand and other Southeast Asian countries, also known as "Vietnamese fish" and "South Sea crucian carp". And because the introduced tilapia, after artificial hybridization, less disease, fast growth, high yield, less spines and other advantages are welcomed by farmers and consumers, called "Fushou fish".
Coptodon zillii|uncontacted tribe
Oreochromis aureus
Why is tilapia the main species of freshwater aquaculture on the mainland?
Tilapia is rich in nutrition and comprehensiveness, rich in high-quality protein, unsaturated fatty acids and various trace elements needed by the human body, which is an ideal food object for human beings. Tilapia are highly adaptable, and although they are freshwater fish, they can survive in low-salt waters, so they can become the object of integrated cultivation in saline-alkali land, turning the "agricultural desert" into a "land of fish and rice". And tilapia can adapt to the low oxygen environment, suitable for large-scale farming, and they also have a strong ability to resist disease, in captivity, almost rarely get sick, not picky eating, low feeding costs, gluttonous growth rate, no intermuscular thorns and other characteristics, so that it has become a very popular economic fish and introduced around the world. In addition, some tilapia also have high ornamental value and are widely liked by ornamental fish lovers.
After tilapia was introduced to the mainland as a food fish, it gradually became the largest alien fish cultured in the mainland, ranking sixth among freshwater cultured fish and first in exotic freshwater cultured fish in terms of production after silver carp, bighead, carp, crucian carp and grass carp. From 1990 to the present, the mainland is the country with the largest output of tilapia aquaculture in the world, maintaining an output of more than 1.6 million tons per year in recent years, occupying a pivotal position in the international aquatic product trade, driving the development of a large number of related industries and the prosperity of employees.
Nile tilapia Oreochromis niloticus|ihunta
Why did tilapia enter the List of Invasive Alien Species for Key Management?
Tilapia like to fight, have a strong sense of territory and young protection habits, and even the female tilapia of the genus Tilapia will hold the eggs in the mouth to hatch, so the survival rate of tilapia juveniles is very high. Moreover, tilapia reproduce very quickly, can lay eggs many times a year, fertilized eggs can hatch after more than ten days, under suitable conditions, juveniles can mature sexually after a season of growth. In addition, they are omnigeneous, non-selective and adaptable to the environment, and after escaping or illegally releasing into natural waters, they will quickly flood and seize the ecological niche of indigenous fish, which will cause a sharp decline in the biodiversity of rivers and lakes. As a result, tilapia tends to flourish in many countries. The Mozambican tilapia Oreochromis mossambicus was listed by the International Union for Conservation of Nature (IUCN) in 2000 as one of the 100 most threatened invasive alien species worldwide; Oreochromis niloticus was included in the List of Invasive Alien Species in China (Third Batch) by the Ministry of Environmental Protection and the Chinese Academy of Sciences in August 2014. Coptodon zillii was listed in the mainland's List of Invasive Alien Species under Key Management by the Ministry of Agriculture and Rural Affairs in December 2022, and is one of the 59 key invasive alien species under management.
Ministry of Environmental Protection and Chinese Academy of Sciences "List of Invasive Alien Species in China (Third Batch)"
Six departments issued the mainland's List of Invasive Alien Species for Key Management
What to think about alien species like tilapia?
How to treat alien organisms is a scientific issue, we do not need to talk about "external" color change, let alone deny the positive role of alien organisms with partial generalizations.
Delicious foods such as tilapia, which often appear on people's tables, as aquaculture objects, play an important role in enriching the people's vegetable baskets, puffing up fishermen's money bags, and helping the development of the fishery industry, and are welcomed by people. At the same time, in the process of farming, if not strictly managed, tilapia entering natural waters may become invasive species, which will lead to the degradation of the ecosystem and functions of the water after flooding, which will threaten ecological security and make people disgusted. Therefore, we need to treat alien species such as tilapia scientifically and fairly, and pay attention to seeking benefits and avoiding harms while exploiting and using. We would like to remind everyone not to discard alien species such as tilapia in the waters of natural rivers and lakes to avoid destructive effects on the ecology of the waters.
Producer: Popular Science China Zhihui Farmers
Author: Zou Qiangjun Deputy Research Librarian of Science Communication of Beijing Aquatic Wildlife Rescue Center, Chief Expert of Science Communication Expert Team of Endangered Aquatic Animal Rescue in North China of the Chinese Fisheries Society
Scientific Review: Researcher Liu Yadan Former Assistant Secretary-General of the Chinese Fisheries Society and Chief Science Communication Expert in China
Coordinator: Wu Yuetong
Proofreader: Zhang Liuyan
Source: Guangming Network - Popular Science China