It is called "soft gold in water" and China now produces it the largest amount in the world!

The golden and slightly charred skin, the soft and glutinous meat rich in collagen, drizzled with salty and fresh sauce, and then covered on steaming hot rice... Such a tempting eel rice is enough to make people drool and be obsessed with it just by thinking about it.

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As a nutritious and delicious fish, eels are very popular around the world. A report from the Food and Agriculture Organization of the United Nations showed that as early as around 2016, the global annual consumption of eels had reached 130,000 tons.

Where do so many eels come from?

China is the world's largest eel farming, processing and exporter.

As early as 1972, my country began to experiment with eel farming. From 2017 to 2021, my country's eel production increased from 217,300 tons to 255,300 tons, accounting for about 75% of the world's eel farming.

How did China develop from scratch to become the largest eel farming and exporting country? What are the experiences and difficulties? Fujian, which has grown into "China's largest eel producing area", is a microcosm of the development of China's eel industry.

Fujian's "Eel Farming Road"

Eel farming in Fujian began in the 1960s.

By the 1980s, live eels had become one of the main products exported by Fuqing City, Fujian Province. According to the local chronicles of Fuqing, by 1989, Fuqing City had become the country's largest freshwater eel breeding, processing and export base, with an output of 671 tons.

Fujian has excellent natural conditions for eel farming.

The climate is warm and humid, the coastline is long, there are many rivers flowing into the area, the hydrological conditions are suitable, and the water quality is good, which is crucial for eels that like clean waters.

In the 1990s, the eel industry had become one of the pillar industries of Fuqing City, with an annual output of about 20,000 tons. At the same time, Fuqing's eel industry chain, technology and experience have begun to spill over to surrounding counties, cities and even other provinces. Guangdong, Jiangxi, Guangxi, Zhejiang and other places have developed local eel industries.

A grilled eel factory in Fujian. Image source: Liu Yadan

While exporting eel farming experience to neighboring provinces, Fujian is also constantly improving and updating eel farming technology to make eel farming more green, efficient, digital and intelligent.

In terms of feed, a research team composed of local enterprises in Fuqing, the Academy of Sciences, well-known domestic fish experts and nutrition feed experts, has overcome a series of technical difficulties in the selection of raw materials, nutritional ratio, appetizing properties, viscoelasticity, production process, production equipment, etc. of eel bait. Finally, in 2008, they successfully developed domestic eel bait with independent intellectual property rights , breaking the technical monopoly of countries such as Japan and South Korea, and making large-scale eel farming possible in China.

Compared with imported eel feed, domestic eel feed costs only 60,000 to 80,000 yuan per ton, which is not only 2/3 cheaper, but also has a higher survival rate and feed conversion rate, while also improving cost and environmental pollution. In 2014, this domestic feed went abroad for the first time and was exported to Indonesia, marking the gradual international competitiveness of China's eel feed technology.

In terms of breeding management, Fujian eel breeding enterprises have also developed an ecological internal and external double-circulation breeding water purification and treatment system and a fish, vegetable and shellfish "breeding and breeding integration" system. The breeding water in the factory is discharged twice a day. After the discharged tail water is coarsely filtered, the clean water returns to the breeding pond. After the sediment is discharged, the liquid is sterilized by ozone and then enters the "fish, vegetable, shellfish" symbiotic breeding and breeding integrated system for purification, and then flows into the reservoir to prepare for breeding again; the solid enters the sewage collection tank and is processed into organic fertilizer to realize the resource utilization of nutrients such as nitrogen and phosphorus in the tail water.

In the "China Eel Valley" in Fuqing, all eel breeding links can be remotely controlled via mobile phone.

Take its precise temperature control system as an example. Eels have extremely high requirements for water temperature. In traditional breeding models, coal and boilers are mostly used to control water temperature. This method is not only costly but also inefficient. At the "China Eel Valley" base, ring-shaped heating pipes are laid near and in the middle of the breeding pond. When the sensor captures temperature changes, it will send the data to the digital breeding platform, and the staff can adjust it in time according to needs. This technology can control the temperature difference of the pool within 0.5℃, greatly improving the accuracy of the breeding environment.

This digital breeding model has increased the survival rate of eels at the base by 10%, and improved both the meat growth coefficient and meat quality.

Relying on the construction of a full industrial chain based on technological innovation and continuous adjustment of product strategies, Fujian now not only ranks first in the country in eel production, but also in the number of eel farming varieties, grilled eel and feed production, and foreign exchange income generated by eel products.

Research on artificial breeding of eel fry is included in the national plan

However, behind the amazing output and huge market demand, there is also a dark cloud hanging over the development of the eel industry.

Eel is the only farmed fish species that relies entirely on catching wild fry, which is why eel fry is known as "soft gold in water".

Why can't eels be farmed artificially? It all starts with their extremely special life cycle.

Eels go through six stages in their life: egg → willow leaf eel → glass eel → thread eel → yellow eel → silver eel. Eels spend most of their lives in rivers, but only when they lay eggs will they swim to the sea thousands of kilometers away from land, which is called downstream migration. They reproduce only once in their lives, and once completed, the eel's life journey will also come to an end.

Because of this unique growth characteristic, it is difficult for scientists to fully observe their reproduction and growth process in the natural environment. Even their breeding location has long been a mystery. It was not until the 1990s that Japanese scientists determined the approximate spawning range of eels - near the Mariana Trench in the western Pacific Ocean.

When eels become "thread eels", they are caught by fishermen using fine fixed nets and sent to nurseries to become artificially cultivated eel seedlings. Image source: Danielle Hall. The Origin of Eels

Furthermore, the sex of eels is not determined at birth, but by environmental factors, and sexual organs only develop in the late stage of the eel's life, that is, the "silver eel" stage. When the population density is high and food is insufficient, eels develop into males, and when the population density is low and food is sufficient, they develop into females. When the population is small, the proportion of females increases, and when the population is large, it decreases. At present, neither wild eels nor farmed eels can naturally mature sexually in an artificial environment.

In order to cope with the "eel crisis", many countries have launched scientific research.

Japan has been researching artificial breeding technology for eels since the 1940s. On July 4, 2024, the Japan Fisheries Agency announced that its fisheries research institute had achieved a new breakthrough in domestic artificial eel breeding technology, reducing the breeding cost from more than 40,000 yen (about 1,805.72 yuan) per eel in 2016 to 1,821 yen (about 82.33 yuan).

Since the 1970s, China has launched research on eel developmental biology and artificial breeding technology in a combination of industry, academia and research, with the support of relevant departments at the national, provincial and municipal levels . In April 2023, the Ministry of Agriculture and Rural Affairs issued the "Notice on the Announcement of the First Batch of National Aquatic Breeding Joint Research Plan", selecting eels as one of the first research targets.

The notice stated that the main focus should be on mass cultivation of artificially bred willow eels, and research should be continued on the optimization of artificial breeding technology of eels, the acquisition of high-quality fertilized eggs and fry cultivation, the survival rate and survival time of newly hatched fry should be improved, the feed formula and fry cultivation equipment for newly hatched fry should be optimized, and efforts should be made to break through the willow eel cultivation technology and ultimately cultivate glass eels; a base for the preservation of eel germplasm resources should be established to form a one-stop technical system for the preservation of eel germplasm resources, the cultivation of reserve broodstock, the ripening and induction of eel broodstock, and the cultivation of newly hatched fry.

At the end of April 2024, the "National Aquatic Breeding Joint Research Plan - Eel Breeding Joint Research Seminar" was held at Shanghai Ocean University. Eel fry breeding was once again included in the national plan.

In addition to studying the technology of artificial breeding of eels, my country is also constantly regulating the development of the eel fry industry.

In my country, fishing for eel fry requires a license, and the fishing must be done at a fixed time, at a fixed location, and in a fixed amount. Otherwise, it is illegal. The punishment is a fine, confiscation of the tools and proceeds of the crime. If the amount involved exceeds 1,000 yuan, it is a criminal offense. In serious cases, the maximum sentence is three years in prison.

In 2024, the Ministry of Agriculture and Rural Affairs held a press conference on the "China Fisheries Sword" law enforcement operation, and added a new law enforcement action to regulate the management of eel fry fishing in "Sword 2024".

Eels are very important aquatic resources and economic fishery species worldwide. In my country, eel farming is also an important industry that drives rural revitalization and development. We hope that research on artificial breeding of eels can make new progress as soon as possible so that the eel industry can truly achieve sustainable development.

References

[1]https://baijiahao.baidu.com/s?id=1776458828302638528&wfr=spider&for=pc

[2]https://www.fjdaily.com/app/content/2024-06/27/content_2623532.html

[3]https://www.163.com/dy/article/FQDR0LCH0517QMLL.html

[4]https://www.fjdaily.com/app/content/2024-06/27/content_2623532.html

[5]https://baijiahao.baidu.com/s?id=1803973095011538248&wfr=spider&for=pc

[6]http://www.chinaeel.cn/index.php?c=content&a=show&id=32183;[7]https://www.customslawyer.cn/index.php/portal/lssf/detail/id/65396.html

[8]https://www.bjnews.com.cn/detail/1711077725129971.html

[9]http://www.fujiansannong.com/info/90013

[10]https://www.farmer.com.cn/2024/07/07/99959043.html

Planning and production

Author: Yixiao Popular Science Creator

Review丨Liu Yadan, Researcher of Chinese Society of Fisheries

Planning丨Yang Yaping

Editor: Yang Yaping

Proofread by Xu Lailinlin

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