[Creative Cultivation Program] "King of Midnight Snacks" or "King of Destruction"? All about crayfish

Author: Kong Lingfeng

Reviewer: Chen Shengjun

When it comes to the "dominant" in the summer food world, you will definitely think of crayfish. The delicious crayfish is rated as the first choice for late-night snacks by many young people. According to the latest report, the total output value of my country's crayfish industry in 2021 was about 422.195 billion yuan, a year-on-year increase of 22.43% (the statistics do not include Hong Kong, Macao and Taiwan, the same below).

However, the origin of crayfish is not so well known. Speaking of this, why don't we first find out its "background" and learn about the past and present of crayfish.

The Chinese name of crayfish is Procambarus clarkii, which is a Crustacean, Decapoda, Crayfish family aquatic animal, native to North America, and later introduced to the surrounding areas of Nanjing, China by Japan around the 1930s, originally for breeding and cultivation as bullfrog feed. However, due to the delicious taste, tender meat and high edible part of crayfish, it was soon discovered as a food ingredient.

After entering the vision of my country's "foodies", there are countless ways to eat it, such as spicy, thirteen spices, garlic... After experiencing large-scale breeding and cultivation, crayfish has defeated many Chinese native crayfish (Northeast black crayfish, Nanjing black crayfish, etc.) because of its omnivorous nature, fast growth rate, strong adaptability and high reproduction rate, and has been widely distributed in the middle and lower reaches of the Yangtze River.

In addition to their tenacious vitality, crayfish are also good at digging holes, which is their innate nature. Crayfish are warm-tropical freshwater shrimps that generally live in permanent streams and swamps, and can also be found in ditches and ponds. In the natural environment, the main purpose of crayfish digging holes is not only to avoid predation by natural enemies, but also to escape the heat or cold in the holes, which is why March to September is usually the peak season for crayfish fishing. However, along with digging holes, the various hazards of crayfish have gradually been exposed.

Combined with the common habitats of crayfish and their habit of digging holes anywhere, coupled with their own super reproductive ability, the title of "King of Destruction" is not undeserved. It often brings consequences such as damaging dams and destroying farmland. In 2013, invasive crayfish were found in the Hani terraces in Yuanyang, Yunnan. As soon as they appeared, they reproduced and dug holes through their own adaptability, causing water leakage and seepage in the ridges, which not only affected the beauty of the terraces, but also seriously affected the growth of crops. In various parts of foreign countries, crayfish also exerted their destructive power, flooding local waters and posing a serious threat to local animal and plant populations. The World Conservation Union (IUCN) even listed crayfish as one of the 100 most destructive invasive species in the world.

When it comes to invasive species, you can think of them as "foreigners" in a biological system relative to "locals", and this guest is not a friendly guest. We all know in biology textbooks that an ecosystem refers to a unified whole composed of organisms and the environment within a certain space in nature. In this system, organisms and the environment, and organisms and organisms interact and restrict each other, reaching a dynamic balance. Natural enemies are an important factor in maintaining the dynamic balance of the ecosystem. The growth of invasive alien species (IAS) is precisely due to the lack of natural enemies. They often grow explosively, snatch resources, and compress the living space of other organisms, which leads to ecological imbalance and even endangers the ecological security of a region or even a country. The characteristics of invasive species are often rapid reproduction and growth, high dispersal ability, and strong ability to adapt to new conditions. Their spread will have a negative impact on the balance of the local ecosystem. Based on the above characteristics, invasive alien species often grow and reproduce more than local organisms in the newly introduced range, and are recognized as one of the main causes of global biodiversity loss.

In addition to crayfish, as of June 2020, more than 660 invasive alien species have been discovered in my country, of which 215 have invaded national nature reserves. The wide range of their involvement cannot be ignored by all of us. In recent years, common ones in our lives include golden apple snails, red fire ants, scavengers (fish used to clean up feces and bait in aquariums for ornamental fish), water peanuts, tilapia, etc. Many of them are "regular guests" in various news reports, and the harm they cause is deeply hated by the general public.

The golden apple snail was introduced as an edible snail in 1981. It looks similar to field snails. There are a lot of parasites in its body. If it is not fully cooked and enters the human body, it will damage nerve tissue. In severe cases, it will cause dementia or even death. In addition, the golden apple snail has a strong reproductive capacity and can lay 30,000 to 50,000 eggs a year. It likes to eat rice seedlings, which is a serious harm to rice production.

The red fire ant, whose Latin name means "invincible ant", is native to South America and has now spread to 12 provinces in my country. It is red in color and highly aggressive. It stings people multiple times in a row and releases venom at the same time. After being stung, it feels like being burned by fire and is usually accompanied by blisters. A few people will have anaphylactic shock and are in danger of death. Ant colonies also often eat crop seeds and fruits, causing agricultural damage such as reduced yields.

In summary, in terms of ecological impact, invasive alien species not only affect the growth, reproduction, and genetics of local species, but also destroy the balance of the ecosystem and resource consumption; in terms of social impact, while causing agricultural losses, they also bring new pathogens that are not common locally, causing new human diseases. In February 2021, the "Supplementary Provisions of the Supreme People's Court and the Supreme People's Procuratorate on the Execution of Determined Crimes (VII)" stipulated the crime of illegally introducing, releasing, and discarding invasive alien species.

When we discover invasive alien species, we should not be blinded by profit, nor should we think of curing everything by "eating". After all, it is very easy to introduce an alien species, but it is not so easy to deal with the consequences it brings.

Content reference:

The "China Crayfish Industry Development Report (2022)" was jointly compiled by the National Fisheries Technology Extension Center, the Chinese Society of Fisheries, and the China Aquatic Products Circulation and Processing Association under the guidance of the Fisheries Administration of the Ministry of Agriculture and Rural Affairs;

China's Ministry of Ecology and Environment, 2019 China Ecological Environment Bulletin;

Article 344-1 of the "Supplementary Provisions of the Supreme People's Court and the Supreme People's Procuratorate on the Execution of Determination of Crimes (VII)"

This article is produced by the Science Popularization China-Creation Cultivation Program. Please indicate the source when reprinting