Source: Qianjiang Evening News
With sharp and fine teeth, a long and flat mouth, and a body covered with scales, this strange fish hidden in the water has attracted the attention of millions of netizens.
Since mid-July, Henan's Ruzhou side has used every effort to catch strange fish and crocodiles, even at the expense of draining the lake. Finally, on August 27, two crocodile eels, one female and one male, were found and treated harmlessly.
Coincidentally, Uncle Li, a 74-year-old guangzhou citizen fishing friend, once caught this "ecological killer" in the Pearl River. However, he took into account the warning of the experts that they must not be released, and kept the crocodile eel at home for fifteen years. Because he knew that once the alligator eel entered the natural waters, it could have a huge impact on the ecological environment. In July this year, the Pearl River Fisheries Research Institute's Foreign Aquatic Organisms Risk Assessment Center received Uncle Li's crocodile eel.
The alligator eel has brought the topic of alien species invasions back to the foreground. According to the 2020 Bulletin on the State of China's Ecology and Environment, more than 660 invasive alien species have been found across the country. The mainland is one of the countries that suffers from serious harm from alien species.
The Qianjiang Evening News and Hourly News reporter connected with Gu Dangen, an associate researcher in charge of the prevention and control of alien species at the Pearl River Fisheries Research Institute of the Chinese Academy of Fishery Sciences, to listen to his stories of dealing with exotic fish in the Pearl River waters.
"Touch the fish" at work, "fish" after work,
Self-proclaimed "Old Fisherman"
The hot summer weather is the best time to monitor the wild – it is the breeding season of many fish, and the population is large and easy to observe. Gu Dangenzheng, an associate researcher at the Pearl River Fisheries Research Institute of the China Fisheries Research Institute, and the fishermen carefully inspected the catches in the nets. They did this work for more than a decade.
Gu Dang'en and his team of 11 people are monitoring foreign fish at a certain point in the West River, one of the tributaries of the Pearl River, these days.
The researchers on this team are almost all "old fishermen". They can skillfully row boats into the river and get out of the nets themselves.
On August 30, they spent three or four hours laying 18 nets at xijiang points. "When we work in the field, we often fall into mud pits, get dirty, and everyone jokes with each other." Gu Dang'en said with a smile.
"The range of alien species is very large, as long as it is alien, it is an alien species." Gu Dang'en said that only after the formation of an invasion can it be called an invasive species.
Therefore, the team will focus on the catch of invasive alien fish, what species? What are the quantities? For a specific species, they will analyze its sex ratio, the number of juvenile fish and other factors to judge its reproduction in the watershed, and provide data support for prevention and control work.
After grasping the specific situation of invasive foreign fish, Gu Dangen and his colleagues will conduct various experiments in the institute.
Gu Dangen introduced that in the face of some exotic fish, biological prevention and control methods can be adopted, that is, to let other fish control invasive fish and reduce the number of invasive fish. "We'll try which fish are more efficient at feeding invasive fry." Because he has to get in close contact with various fish every day, Gu Dang'en jokes that he is "touching fish at work".
Gu Dang'en, who was off duty, liked to fish. He had been fishing since he was seven or eight years old, and perhaps the seeds of doing it had been planted since that time.
Old anglers caught alligator eels,
After fifteen years of cultivation, I have nearly doubled my body size
"I've been raising this crocodile eel for fifteen years, and now that I'm old enough to keep it, I want to find him a place to go." Uncle Li, 74, is worried.
Last month, Mr. Gu received a call from a reporter from Guangzhou Television. It turned out that this citizen Uncle Li was a fishing enthusiast who caught this crocodile eel in the Pearl River fifteen years ago.
After seeing this strange "duck-billed monster fish", Uncle Li consulted the local fishery and aquaculture department and learned that it is one of the world's top ten fierce freshwater fish. If a population is formed in natural waters, it will seize the growth space of other fish, and the fishery and aquaculture department reminds Uncle Li that it must not be released.
Because of this sentence, Uncle Li took a water tank at home to raise crocodile eels, and raised them for fifteen years. When he first picked it up, Uncle Li measured it, and this crocodile eel has a body length of 36 cm and a mouth length of 6 cm. In fifteen years, due to its continuous growth, Uncle Li replaced the fish tank three times.
Crocodile eels grow fast. When Gu Dang'en visited Uncle Li's home, this crocodile eel was already a big guy with a body length of about 70 centimeters. The crocodile eel generally has a lifespan of several decades and is a very long-lived species of fish.
Crocodile eels are fierce, coupled with large size, this year's 74-year-old Uncle Li is a little weak to raise, but suffering from the inability to find a relay person, can only turn to the media. In July this year, Gu Dang'en received the crocodile eel and raised it in the Pearl River Fisheries Research Institute's Foreign Aquatic Organisms Risk Assessment Center.
Previously, Gu Dang'en had successively received four crocodile eels from the society and raised them in the center, the longest of which was three or four years. Some of these crocodile eels were caught in the wild by citizens, and some were found when the lake was released. This partly reflects the fact that alligator eels are distributed in the wild.
"Judging from the numbers available, it has not yet reached the point of flooding. However, it is necessary to do a good job in science popularization as soon as possible, so that more people realize its harm, and the effective prevention and control of crocodile eels can be realized earlier. Gu Dangen said.
Zhou Zhuocheng, chairman of the China Fisheries Association's Native Aquatic Organisms and Water Ecology Professional Committee, also told the Qianjiang Evening News hourly news reporter that the crocodile eel is a large predatory fish, with a particularly strong body and almost no natural enemies. Even in the place of origin, only crocodiles and larger fish are likely to prey.
"After the alligator eel enters the natural water body, it may prey on local fish in large quantities, which has a greater impact on the ecology." Zhou Zhuocheng speculated that crocodile eels appear in natural water bodies, most likely because someone bought them as ornamental fish, did not want to raise them, and abandoned them at will.
After the crocodile eel appeared, netizens had a heated discussion about how to deal with it. But Zhou Zhuocheng said that the crocodile eel has no role other than as an ornamental fish. "Because its meat is not tasty, the eggs are poisonous. In the place of origin, because of its predatory characteristics, it is more fun to catch it, so it is used for fishing, but we will not develop it here for fishing. Zhou Zhuocheng said.
Prevention and control of invasive alien species, everyone can participate,
Doing a good job in science popularization is the key
Engaged in the prevention and control of foreign fish invasion for many years, Gu Dangen they recognize the importance of science popularization, "If the early years can do a good job of science popularization, there will not be so many things now." ”
The African giant snail was an invasive species that entered the continent in the first half of the last century and is now very common in southern China. After being introduced, some people tried artificial breeding, but they were eventually rejected by the market due to poor taste and the spread of disease.
"In fact, if everyone catches it after seeing it and then disposes of it, the prevention and control situation can improve a lot." Gu Dangen said that because of the excessive description of some reports, saying that "large snails cannot be touched", "there are 60 million parasites" and so on, everyone dare not touch it.
In Gu Dangen's view, the prevention and control of invasive alien species is something that everyone can participate in, as long as personal protection is done, "wear a glove, and then clean it in time after catching it, don't go to eat without washing your hands, there will be no harm." ”
The "scavenger" of fish species, which is very common in South China, is also due to the "invasion" caused by the untimely popularization of science in the early years. "Scavengers" were first introduced as an ornamental fish, although they are ornamental fish, their appearance is not beautiful, and they are artificially released and discarded
A lot of that. For example, in the early years, after the fishermen caught it, they didn't know it, and it was useless, so they threw it back into the river.
"Scavengers" had a strong reproductive capacity, and there was no fishing pressure at the time, so the number of "scavengers" increased, while the number of other fish became smaller and smaller. In some serious sections of the river, fishermen can catch more than a hundred in one night.
Over the years, because the team often went to the river to monitor, the fishermen knew them. "Every time we meet, the fishermen remember when we last came." Gu Dang'en said. Each time the team arrives at a point, local fishermen are very active in running over to show them new fish they encounter while fishing, or ask them for help with exotic species.
The improvement of fishermen's ecological awareness has greatly helped the prevention and control of alien species. When the team discovers new species, they often communicate with the old fishermen, "Maybe we found a new fish, but I don't know when it first appeared, but the old fishermen know." They've been fishing all their lives, and although they may not be able to name a fish, they know exactly what the fish looks like. Gu Dangen said.
The first census of invasive aquatic animals in our province,
Fushou snails are found the most
"Judging from the current census situation, crocodile eels have not been found, with fushou snails being the most and crayfish second." Zheng Tianlun, head of the industrial development section of the aquatic products promotion station of the Zhejiang Provincial Department of Agriculture and Rural Affairs, told the Qianjiang Evening News hourly news reporter.
In this year's census of invasive aquatic animals from outside Zhejiang Province, Fushou snails were found with the highest frequency, and Fushou snails were very destructive, "It eats everything, and once it enters the rice field, it will nibble on rice seedlings, seedlings, etc., which has a great impact on grain production." Zheng Tianlun said that there are currently physical control, agricultural control, biological control, chemical control and other measures, but the most important cleaning method is still manual removal, the Provincial Academy of Agricultural Sciences and other units are also studying how to improve the efficiency of biological control.
Zheng Tianlun introduced that the census is based on eight major river systems, focusing on 6 invasive species such as tilapia, leopard striped wing catfish (scavenger), crocodile eel, Fushou snail, red-eared painted turtle (Brazilian turtle), bullfrog and other foreign species that need attention, such as protocrayfish (crayfish).
"Knowing their distribution and number, we can more specifically formulate prevention and control measures and determine the focus of prevention and control research." Zheng Tianlun said that this is the first time that Zhejiang Province has comprehensively carried out the census of invasive aquatic animals from outside. Comprehensively find out the general situation of invasive aquatic animals in our province, establish a data file of invasive aquatic animals, improve the database of invasive aquatic animals, and provide basic data support for the scientific prevention and control of invasive aquatic animals.
Source: Qianjiang Evening News Hourly News Reporter Pan Lu Trainee Reporter Wang Xiaoyi