A "new" fish was discovered in the Yangtze River? Good news for the "old" fish as well →

We have discovered a new Yangtze River elf! According to a Xinhua News Agency report on May 15, Chinese researchers discovered a new fish species in a karst cave underground river during a field survey in the Wujiang River Basin in the upper reaches of the Yangtze River. They named it "Guiyang Golden Line Carp".

It is exciting to discover “new” fish in the Yangtze River, but it is also exciting to see that there is good news for the “old” fish in the Yangtze River: three years since the implementation of the ten-year fishing ban policy in the Yangtze River, the population of native fish in some waters of the Yangtze River basin has been observed to have recovered to a certain extent!

Figure 1: A new fish species discovered by Chinese researchers in the upper reaches of the Yangtze River - the Guiyang golden line barb (Source: Xinhua News Agency video screenshot)

01 An indispensable role among the “old” fish in the Yangtze River: migratory fish

Among the native fish species of the Yangtze River, many are migratory fish . Their special living habits make their survival and reproduction particularly vulnerable to human activities such as overfishing, water pollution, water conservancy projects, and shipping . So what are migratory fish?

According to the purpose of survival , fish migration can be divided into three categories:

▶Reproductive migration: The periodic movement of fish to reproduce .

▶Foraging migration: the periodic movement of fish in search of food .

▶Vertical migratory fish move up and down in the water to avoid light, enemies, and temperature (only occurs in the ocean).

According to the direction of migration , fish migration can also be divided into three categories:

Table of migratory fish types (Compiled by Hu Kai)

Note [1]: The situation of river-lake migration for reproductive purposes is relatively complicated. The migration of alligator carp and the four major carps, namely black carp, grass carp, silver carp and bighead carp, from lakes to the Yangtze River for reproduction can be regarded as river-lake migration.

02 Anadromous fish

The famous "Three Fresh Fishes of the Yangtze River": shad, knife fish (Knife fish) and pufferfish (Dark-spotted Puffer), and the Chinese sturgeon, known as the "giant panda of the water", migrate upstream during the breeding season, a method called upstream migration ; the adults of these fish generally live in the ocean (some populations of knife fish live in fresh water all their lives, are smaller in size, and are commonly known as "lake knife fish"); when the breeding season arrives, they will swim upstream, enter fresh water to lay eggs and reproduce, and return to the ocean after completing reproduction; the hatched fry will feed and fatten in fresh water for a period of time, and then swim downstream to live in the ocean;

Figure 2: One of the three delicacies of the Yangtze River, the "Knifefish" (Source: Screenshot of Hubei News video)

Figure 3: One of the three delicacies of the Yangtze River, the dark-striped pufferfish (Source: Xinhuanet)

The Yangtze River is an important breeding ground for these migratory fish. Take the knife fish, one of the three fresh delicacies of the Yangtze River, as an example. Due to historical overfishing and water conservancy projects and other factors, it has been difficult for the Yangtze River knife fish (the migratory ecological type of knife fish) to form a fishing season for a long time.

Before and after the implementation of the fishing ban, the number of saury has rebounded, and it has reappeared in some sections of the river where it had been extinct for many years. For example, Shanghai Chongming District had already carried out fishing bans before the implementation of the Yangtze River fishing ban. In a fish monitoring in the Yangtze River in March 2021, researchers caught nearly 200 kilograms of saury in one net; in February 2023, the Ministry of Agriculture and Rural Affairs announced at a press conference that saury can now migrate upstream to the waters of Dongting Lake, which has reached the farthest area that saury can migrate to in history.

03 Migratory fish

Another type of migratory fish in the Yangtze River migrates to the sea , the most typical of which is the Japanese eel, commonly known as "white eel" and "eel". Unlike the razorfish and shad, the Japanese eel reproduces in the ocean. Sexually mature Japanese eels will swim to the deep sea near the Mariana Trench in the Philippines for the only reproduction in their lifetime, and then die.

Newly hatched eels are called willow leaf eels ; after undergoing metamorphosis, willow leaf eels will grow into glass eels that look similar to adult eels, migrating to the estuaries of rivers that connect to the sea, such as the Yangtze River, and then swimming upstream into the river; glass eels will develop into yellow eels in fresh water, grow and fatten for several years until they reach sexual maturity, and then return to the ocean to reproduce.

Figure 4: The development process of Japanese eel (Source: Wikipedia)

Because Japanese eels are rich in fat and have very delicious meat, they have always been a popular food ingredient, so they have been overfished and are currently listed as endangered species on the IUCN Red List. The artificial breeding technology of Japanese eels is very immature, so the "farmed" Japanese eels we see on the market are actually wild eel fry caught in the estuaries of the Yangtze River, Qiantang River and other rivers, and then fattened and raised in an artificial environment.

Figure 5: Japanese eel (Source: Wikipedia)

With the implementation of the ten-year fishing ban, it is illegal to fish wild Japanese eels in the main stream of the Yangtze River and in large lakes connected to the river. As for fishing for eel fry in river mouths, the current law also has strict quota controls on fishing time, use of nets, and fishing quantity . Any violation will be considered poaching and will be severely punished. With the implementation of these protection measures, coupled with the strong reproductive capacity and adaptability of Japanese eels, their numbers are expected to gradually recover like the northern bluefin tuna, which was also once listed as an endangered species, and escape the endangered predicament.

04 Migratory fish

Not all freshwater migratory fish have to enter the ocean in their lifetime. Some migratory fish living in the Yangtze River, such as the common "four major carps": black carp, grass carp, silver carp and bighead carp , as well as the carnivorous bream, silver carp and bighead carp , and the huge white sturgeon , will migrate between rivers and lakes . These fish will enter the deep lakes of Tongjiang in autumn and winter for fattening and overwintering; in spring and summer, especially during the flood season, they will enter the main river channel for reproduction and spawning. In addition, some migratory fish will migrate back and forth between the upper and lower reaches of the Yangtze River. For example, the Yangtze sturgeon and white sturgeon will spawn and reproduce in the Jinsha River waters in the upper reaches of the Yangtze River, and the young white sturgeons will go downstream to the Yangtze River estuary to feed and fatten in preparation for overwintering; bream, silver carp and bighead carp will lay floating eggs in the upper reaches of the Yangtze River, and the fish eggs will gradually develop and hatch in the process of drifting downstream; the four major carps will also go upstream to the upper reaches of the Yangtze River or the tributaries of Tongjiang to spawn during the breeding season.

Figure 6: White sturgeon (Photo provided by Shen Yuxi)

Figure 7: Juvenile Chinese sturgeon (Source: Wikipedia)

The blocking of the migration routes of these fish by water conservancy facilities and the resulting changes in hydrological conditions, as well as overfishing, especially the use of illegal fishing methods such as mazes, family-destroying nets, ground traps, rolling hooks, electric fishing, and blasting fish in lakes and tributaries connected to the river, will have a very serious negative impact on the normal breeding cycle of these fish.

With the implementation of the fishing ban policy, the population of the four major carps, migratory fish that lay floating eggs, has rebounded, and the long-lost mullet has reappeared in the waters of Hubei, Jiangxi and other places. In July 2021, the Hubei Fisheries Science Research Institute conducted a field survey of fish resources in key waters of the Yangtze River along Dongting Lake, and found two mullets in the "South Dongting Lake Grass Turtle and Chinese Soft-shelled Turtle National Aquatic Germplasm Resources Protection Area". It has been 20 years since the last time mullets were found in Dongting Lake.

The Yangtze River freshwater ecosystem, which was once devastated by over-exploitation, has begun to regain vitality thanks to the implementation of protective measures.

Author: Hu Kai, science research instructor, CCTV-9 documentary channel science consultant

Reviewer: Yu Fandong, member of the popular science expert team of the Chinese Society of Fisheries, PhD of the Pearl River Fisheries Research Institute of the Chinese Academy of Fishery Sciences

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.