Speaking of Egyptian pond catfish, everyone should be familiar with this fish, which is an exotic breed introduced from Africa, and is also known as leather-bearded catfish and Egyptian bearded catfish in China.
Native to the Nile River Basin, Egyptian pond flounder has the characteristics of low oxygen tolerance, strong adaptability and fast reproduction, and was introduced to China as a cultured species in the 1980s, with a large scale of breeding in South China. However, due to various human factors, the introduced Egyptian pond mackerel soon escaped into natural waters and gradually developed and grew.
Egyptian pond fish (Clarias gariepinus)
A 2016 domestic survey showed that the Egyptian pond mackerel has established a natural population in South China, which can not only overwinter smoothly, but also reproduce naturally. At present, the Egyptian pond flounder has spread to many rivers in the south, such as the Pearl River system, the JianJiang River, the TanJiang River and the Nandu River in Hainan Province, becoming one of the most invasive alien species.
<h1 class="pgc-h-arrow-right" > Egyptian pond carp: a "fertility machine" that breeds 5 times a year</h1>
Taxonomically , the Egyptian catfish belong to the order Catfish , and the vast majority of its members are highly adaptable , such as the domestic catfish , southern catfish , and yellow-jawed fish. Catfish have special auxiliary respiratory organs and can survive normally even when the oxygen content in the water is very low, so they can also adapt to high-density farming.
Egyptian pond flounder at the drainage point
Compared with the domestic native catfish, the Egyptian pond mackerel is more adaptable to the water environment, and also has the characteristics of eating miscellaneous and large food, not only can prey on a variety of fish and shrimp in natural waters, aquatic insects, and even animal carcasses - this is why some people call it "garbage fish".
Adult Egyptian pond flounder can grow to 1 to 1.5 meters, the largest individual can grow to 1.7 meters, and the weight is as high as 60 kilograms, which is enough to catch up with the size of an adult. Because of its large size, the Egyptian pond mackerel can swallow many large prey and can also "leapfrog" to kill water birds that stay on the surface of the water, such as black water chickens. Even more surprising is that the Egyptian pond mackerel can even jump out of the water to fill its stomach and kill poultry and small mammals that drink water on the shore.
Giant Egyptian pond carp in the Nile Valley
Not only that, but the Egyptian pond mackerel also has a strong reproductive ability. Egyptian pond bream are typical of large catfish, but the youngest sexually mature individuals begin to reproduce at around 100 grams. Adult female pond mackerels can breed 4 to 5 times a year, and after each spawning, there are many mature reserve eggs in the ovaries, which can be produced in batches.
Jump on the Egyptian pond flounder on the riverbank
Generally speaking, egyptian pond fish only need 7 to 10 months to mature, and the larger the body, the stronger the fertility. In the captive breeding environment, the spawn volume of Egyptian pond mackerel is generally between 50,000 and 150,000 pieces, and the fertility of wild pond fish is even stronger, and the spawning capacity can reach 200,000 to 250,000 pieces, which can be called a powerful "fertility machine".
Many of the characteristics of the Egyptian pond mackerel make this species at risk of "getting out of control". In fact, this species has caused a lot of turmoil in India, Vietnam, Brazil and Indonesia, not only will it hybridize with other bearded catfish, but also spread pathogenic bacteria and parasites, causing a lot of losses to the aquaculture industry.
< h1 class="pgc-h-arrow-right" > wild Egyptian pond mackerel was found in South China, and the Pearl River Basin became a "hard-hit area"? </h1>
On the list of common alien species in Guangdong waters, the Egyptian pond mackerel is prominently listed, and like species such as scavengers, blue gill sunfish, and piranhas, it has become the object of everyone's "verbal criticism".
Wild Egyptian pond mackerels are not well received, wind ratings are quite poor, and if wild populations get out of control, they are likely to cause serious ecological damage like tilapia. Wild pond mackerel can crowd out native fish by encroaching on ecological niches, preying on competition, and even potentially triggering a survival crisis for species.
Egyptian pond mackerel floods in some of its rivers
In order to find out the number and distribution of Egyptian pond mackerel in the southern part of Qinghua, in 2011, the staff of the Pearl River Fisheries Research Institute launched a thorough investigation, and the sampling area was mainly the North River, East River, West River and surrounding waters of the Pearl River system.
Through more than three years of field investigation, the researchers collected a total of 229 samples of wild Egyptian pond mackerel, including many mature female individuals. After careful measurement, the body length of these Egyptian pond carp is between 11.4 and 62.4 cm and the weight is between 12.6 and 2097 g. Among them, small catfish under 20 centimeters account for 60%, basically one-year-old individuals.
Survey overview of Egyptian pond flounder in the main waters of South China
Worryingly, Egyptian pond flounder over 2 years old have been found in many sampling sites, 3-year-old Egyptian pond flounder has been found in Jianjiang, Beijiang and Huadihe, and 4-year-old Egyptian pond flounder has also been found in Haizhu Lake. These cases have shown that Egyptian pond flounder can overwinter and breed normally in the natural waters of southern China.
Where the Egyptian pond flounder was found (black square area in the picture)
In addition, in the investigation from April to October 2014, a large number of Egyptian pond mackerel juveniles were also found in Haikou, Wenchang and other places in Hainan Province, which further proved the strong population building ability of Egyptian pond mackerel. Considering the voraciousness and strong fecundity of this species, the "chaos" brought by the Egyptian pond mackerel can no longer be ignored.
< h1 class = "pgc-h-arrow-right" > the wild expansion of Egyptian pond mackerel, the Yangtze River and the Yellow River have also been "lost"? </h1>
Under natural conditions, the most suitable water temperature for the growth and breeding of Egyptian pond carp is 25 to 32 °C, which can be said to be mixed in the rivers and lakes in the southern region. However, unlike tilapia, Egyptian pond mackerel can withstand low temperatures of 5 to 10 °C, and can also adapt to harsh water quality environments such as sewers and sewage outlets. Therefore, neither water temperature nor water quality is the "ecological red line" that prevents the Egyptian pond mackerel from expanding to the north of our country.
The middle and upper reaches of the Yangtze River
In fact, in the upper reaches of the Yangtze River in the Yibin River section and the lower Reaches of the Anqing River, many people have found wild Egyptian pond flounder. The main reason is that there are 2 points: one is breeding escape, and the other is blind release.
Due to the easy rearing, infrequent disease and high yield of Egyptian pond mackerel, many farmers in the Yangtze River Basin will cultivate this fish. In addition, there are many heavy rains in summer along the Yangtze River, and fish farmed in reservoirs and mountain ponds can easily flood the embankment, which undoubtedly further increases the risk of escape of individuals.
Artificial culture of Egyptian pond mackerel
There is also an important source of Egyptian pond carp in the Yangtze River - blind artificial release. The release activity has a long history in China, dating back to the Spring and Autumn Period and the Warring States Period, especially after the introduction of Buddhism to China, and the continuous and extensive release customs have been formed in the north and south of the great river. However, due to the lack of scientific publicity, many species that are not suitable for release have been blindly released, such as Brazilian turtles, alligator eels, scavengers, tilapia and so on.
Blind release is actually a disguised "killing", but the release behavior is almost uncontrollable, and at present, it can only strengthen the ecological concept of the people through publicity and science popularization, and reduce the phenomenon of blind release.
Not only the Yangtze River, but also the section from the bottom of the yellow river to the estuary of the Yellow River has also found wild Egyptian pond flounder, for the reasons of the above two points.
The mouth of the Yellow River and the Yellow River Delta
Some people may ask, is it not a double victory to kill two birds with one stone by inviting the Egyptian pond carp in the wild to the table, which not only provides rich nutrition, but also eliminates the ecological crisis?
In theory, it is indeed possible to do this, but at the executive level, it is not an easy task.
First of all, the distribution area of wild Egyptian pond carp is too wide, involving many water systems, and it is not realistic to "catch all wild individuals". Secondly, due to the unknown source, not many people are willing to eat Egyptian pond fish, coupled with the bad reputation of "garbage fish" and "sewer fish", consumers are even more jealous.
Egyptian pond flounder
What's more, South China itself is a "big family" of aquaculture, rich in a variety of valuable economic aquatic products, and there are many edible fish for consumers to choose from, so that the Egyptian pond mackerel is not very attractive.
In short, the wild Egyptian pond carp has become a big hidden danger, and no effective targeted measures have been taken in China. For the reproduction of wild populations, it is still necessary to strengthen monitoring and strictly prevent the flooding of this alien species.
What do you think of the Egyptian pond mackerel? Feel free to leave a message in the comments section to discuss!
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