Releasing the scavengers? This is not accumulating merit, it is committing sin

Recently, a piece of news about "releasing scavenger fish" has become a hot topic. According to reports, on the day of the Mid-Autumn Festival, many people released scavenger fish in the Chengbi Lake Reservoir in Baise City, Guangxi, saying "Everyone who sees it will be blessed" while releasing them.

The police have intervened in the investigation｜Jimu News

However, releasing catfish is not only not a good thing, but it will also damage the ecological environment - after all, catfish is a well-known invasive species.

01

From fish tanks to natural water bodies

Many people have heard of scavengers, and some people call them shit-eating fish, sucker fish, etc. They can be said to have successfully entered the lives of the general public from the traditional aquarium circle. In a narrow sense, "scavenger" refers specifically to the leopard fat catfish (Pterygoplichthys pardalis), which belongs to the family of catfish in the order Siluriformes; in a broad sense, "scavenger" refers to fish that look similar to the leopard fat catfish and are closely related to it and can be used to clean fish tanks.

Leopard catfish｜Richwales / wikimedia

There are more than 680 species of fish in the family Catfish, all of which are relatives of the scavenger. The name Catfish may sound unfamiliar, but it has another relatively familiar name in China - Heteromorpha , especially in the aquarium circle, which is a very popular type of ornamental fish .

Armoured catfish have several distinct characteristics: a sucker mouth with teeth , protective bony plates on the body (hence the name "armoured catfish"), and whiskers that are sensitive to touch. This type of fish comes mostly from tropical and subtropical areas of South America, and is distributed in Brazil, Panama, Costa Rica and other countries.

Illustration of the body structure of catfish｜"The World of Small Labyrinth Aliens"

Many species of catfish have been introduced into China, and most of them exist in the aquarium circle. However, the leopard catfish is the only one that is not doing well.

The scavenger (specifically leopard catfish, the same below) was introduced to China as an ornamental fish in the 1990s. After that, it has been sought after by the aquarium market and the rise of artificial breeding, and the stock market has continued to rise. The scavenger grows quickly and can reach sexual maturity in just two years. It is often used as a companion fish in the fish tank to assist in cleaning .

The breeding threshold of scavengers is low , so more and more farmed scavengers enter the market, and the price falls. Some players who don't want them will throw scavengers into natural freshwater bodies . Scavengers not only survive in many freshwater bodies in China, but even establish wild populations, so that the bottom fish caught in some freshwater river systems are scavengers. This invasive behavior has also had a negative impact on the local ecological environment.

In addition, due to the huge reproduction volume and the fact that it can be directly collected and sold in the wild, the price of the scavenger fish has continued to fall and has reached the level of entry-level ornamental fish . Although they look similar and do not seem to be much different to laymen, many of the scavenger fish's imported relatives are difficult to reproduce and have limited imports, so their prices remain at the player level. In this way, the scavenger fish has not only become the cheapest in the family, but has also been abandoned in natural waters.

The picture above is the common tool fish in the aquarium circle, the camouflage beard (Ancistrus sp.), and the picture below is its artificially improved variety, the golden beard. Both are common catfish of the family Catfish, and many people mistakenly think that they are small scavengers | flickr; Seafood Knowledge

02

Food or pet

In fact, many large South American ornamental fish introduced to China are common edible fish in their places of origin ; vice versa, such as the common kilo fish on the tables in Yunnan and Guizhou. Therefore, outside of the places of origin with rich resources, whether an ornamental fish that can reach edible size can be served on the table often depends on whether you can afford it (laughs).

However, such a thing seems impossible to achieve for an ordinary scavenger.

In fact, the scavengers caught in the major natural water systems are not small, with a body length of 20 to 30 centimeters, and individuals weighing about half a pound can often be caught; the largest scavenger captured in history was 52 centimeters long and weighed nearly 1.3 kilograms. So, what is the limit for scavengers to be used as food?

If you have ever raised or caught a scavenger, you might want to think about the answer first｜Derek Ramsey / wikimedia

The main reason lies in the body structure of the scavenger. First, the scavenger's body is protected by hard bone plates. There is basically no muscle tissue in the head and thorax except for the bone plates. Only the posterior side of the body has obvious muscle tissue for consumption, so it appears to have less meat . Secondly, the appearance of the scavenger makes it difficult for many people to accept it as a food. At the same time, due to its hard shell and time-consuming cooking , it is not very popular among ordinary people.

Many people in China have no choice but to throw or discard the scavengers they catch. Scavengers that reach edible size sometimes cannot be your pets (you don't want to keep them) or your delicious dishes. However, in the scavenger's native place, some catfish can be delicious ingredients, which can be grilled or made into soup.

The soup is made of fish balls made from scavenger meat｜eattheinvaders.org

03

From fleeing and flooding to successful invasion

As mentioned above, the scavenger can survive and reproduce in the wild in China. It is not only known to ordinary people, but also "alarmed" the government. The "famous" scavenger has been included in the "List of Alien Invasive Species in China (Third Batch)" issued by the Ministry of Ecology and Environment of China. Everyone jokingly calls the scavenger the most successful invasive species - not only does it have almost no natural enemies, but even the Chinese who love to eat can't do anything about it (but Calendar Lady wants to reiterate with a serious face: it is almost impossible to solve the problem of species invasion by relying on foodies).

As a tropical and subtropical fish, the scavenger has successfully survived the winter in the natural waters of southern China and even in North China. Because of the armor on its back, even carnivorous fish in the river can't do anything to it . The scavenger is an omnivorous fish that searches for food at the bottom of the water for a long time, so it eats a lot of underwater plants, eggs of native fish, some fry , and even sucks and bites other fish. In waters lacking oxygen, the scavenger can also rush to the surface of the water and use the oxygen in the air to continue to survive.

No matter how strong it is, there are still otters and other animals in its native habitat that can catch and eat catfish, but there is a lack of natural enemies of catfish in my country's natural environment｜Bernard DUPONT / flickr

The reproductive capacity of the scavenger should not be underestimated. In its native habitat, the existence of dry and rainy seasons limits the breeding period of the scavenger, but the scavengers that have invaded the waters of southern China have a longer breeding period . They mainly lay eggs in autumn and winter, with a single egg laying of more than 1,000, and can lay eggs every month during the peak breeding season .

During the breeding season, scavengers will dig holes near the water surface on both sides of the river to mate , and then the males will take care of the fertilized eggs until the young fish can move freely. This habit not only causes the embankments on both sides of the river to become increasingly loose , but also the offspring have a high survival rate due to the care of the parents and the lack of natural enemies. As a result, scavengers have naturally established wild populations in China.

In 2019, a study on the population of scavengers in Guangzhou's freshwater system pointed out that the number of its wild population is currently on the rise, and necessary containment measures are urgently needed. Scavengers are not only rampant in China, but also in parts of North America, the Philippines, Malaysia, Bangladesh and other regions in Southeast Asia. Therefore, releasing scavengers may seem to save their lives, but in fact it puts more native fish in danger.

In the southern Chinese water system, sometimes you can catch so many large scavengers with one net, but I have no appetite at all when I see them｜J. Lee

04

A scavenger eats shit? You're overthinking it

There have been rumors that the scavenger fish is a garbage fish and a poop-eating fish. Aquarium players buy it just to let it eat the poop of other fish in the tank.

When it is young, the scavenger feeds on algae, diatoms and some animal and plant debris on rocks or bottoms ; as it grows up, it consumes more animal food to maintain its energy consumption. Therefore, in addition to algae, fish eggs and some young fish are also its food sources. It is more convenient for the scavenger in the aquarium to eat fish feed fed by humans than to scrape and nibble on the moss on the wall of the fish tank.

The popular belief that fish poop is eaten comes from the fact that scavengers constantly use their suction cups to suck and nibble at the bottom of the fish tank when searching for food, which indirectly disturbs or crushes the fish poop at the bottom of the tank , making it seem to disappear. People therefore mistakenly believe that the fish poop is eaten by scavengers.

Just use a suction cup like this to suck at the bottom of the tank｜javanbazar.com

In the absence of food, scavengers do break up feces and ingest the edible parts, but they generally do not actively eat poop . On the contrary, scavengers are masters of pooping, and because of their long digestive tracts, they mostly produce long feces and excrete them frequently.

What the scavenger can really help with is to remove most of the algae that hinder the appearance of the fish tank wall . In addition, the scavenger does not mind sucking the body surface of other fish in the fish tank (especially sick and weak fish), but this will damage the body tissue of other fish and cause harm to them.

Cucumbers can also be eaten with relish｜aerometal1973 / youtube

The scavenger fish is a magical fish, not only because of its tenacious vitality, but also because no one can do anything to it.

1. Currently, in many freshwater bodies in southern China with suitable environments, the scavenger continues to grow in population. Due to the lack of predators, other fish or birds may even be choked to death by the hard exoskeleton of the scavenger after swallowing it, and even people find it difficult to deal with them;

2. During the breeding season, scavengers dig holes on both sides of rivers and other freshwater bodies, which will affect the stability of embankments and easily cause river bank erosion;

3. Scavengers will also destroy the diversity of the original ecosystem by eating the offspring of other fish and aquatic plants in the waters where they live for a long time. How to deal with such invasive species more effectively is a challenge facing all of us. The "Biosafety Law of the People's Republic of China" that came into effect in April last year stipulates that anyone who releases or discards alien species without authorization shall be ordered to catch or retrieve them within a time limit and be fined.

Whether out of love for the ecological environment or out of responsibility for yourself, please do not release animals at will.

Author: Seafood Knowledge

This article comes from the Species Calendar, welcome to forward

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