Spring is the golden season of wild fishing, during this period some people can connect rods, burst protection, some people can catch the yellow river carp with golden scales and red tails, and some people can catch a cocked mouth, but if someone says that he caught a strange fish with a sharp mouth in the Pearl River, do you believe it?
Recently, some anglers posted on the Internet that he and his friends were fishing in the Pearl River, and the friend caught two mandarin fish in a row, but his float did not move at all, and when he planned to change the fishing position, the float suddenly disappeared into the water. The angler excitedly lifts his rod in both hands - the pull is so big! The fishing rod reveals a beautiful waist, the fish riveted in the water to "rampage", one will rush to the left, one will drill to the right, until the fish is tired, the angler drags it to the shore, it turned out to be a strange fish with a sharp mouth - crocodile eel.
Ferocious alligator eel
Let's start with a brief introduction to the alligator eel. Crocodile eel is a large and ferocious fish species, is the largest of the seven species of garfish in North America, the heaviest more than 160 pounds, up to 3 meters long, most of the time living in fresh water, occasionally in brackish water.
Carnivorous and ferocious are the biggest characteristics of alligator eels, but they do not chew, and they rely on raw swallowing, and swallow 1/4 of the food of the body at the largest time. The surface of the alligator eel has a layer of diamond-shaped glaze hard scales, as if wearing steel armor and iron armor, protecting it tightly! In the home of the alligator eel, the Indians would take off the scales after catching the crocodile eel and treasure it as a gemstone. Because of this, the alligator eel is the "number one overlord" in rivers and lakes, firmly occupying the tip of the food chain.
When exactly did alligator eels enter the mainland? There is no way to verify it, but it is said that it was introduced as a pet fish. In 2004, a small crocodile gar with a length of 85 centimeters and a weight of 12 kilograms was found in Xiushan Park in Wenzhou, Zhejiang Province, which is the earliest record of wild crocodile eels in China.
After nearly two decades of breeding, there are signs that crocodile eels have "camped" in many waters in the southern part of the continent, although the number is not so large. For example, in 2020, the fishing team caught a small alligator with a length of 0.9 meters and a medium-sized alligator eel with a length of 1.2 meters in Baiyun Lake in Guangzhou.
However, crocodile eels have rough flesh, highly toxic internal organs and eggs, and have not yet found a better treatment method.
Exotic fish species have become dominant fish species in the Pearl River
Crocodile eel is only one of many exotic fish species, in fact, foreign fish in the Pearl River has long been "anti-guest-oriented" has become the dominant fish species. According to the data, in the 1960s and 1970s, the number of fish species in the Pearl River waters exceeded 500 species, including carp, mud carp, sea bass and four large fish, as well as duck-billed golden-threaded catfish, Guangdong bream and other characteristic fish species.
When the fisheries department investigated the Pearl River again in 2018, the number of fingerlings had dropped to 438 species, and the structure of fish species had also undergone tremendous changes, with a large number of exotic fish species flooding the Pearl River, and many had become dominant fish species.
In the mid-to-late 1980s, there were only 3 exotic fish species in the Pearl River, which increased to 9 in 2010, became 15 in 2015, and is likely to exceed 20 species by 2021. These exotic fish include tilapia, scavenger, rusta, short-lipped giant carp, leather-bearded catfish, wheat carp, etc., including alligator gar.
Why are exotic fish so tough? For example, a case about tilapia, Lao Wang is an old fisherman in Yangjiang City, Guangdong Province, with more than 20 years of fishing experience, in 2013 in a section of the Pearl River can catch 150 kilograms of fish per day, of which carp, mud carp about 40 kilograms, the remaining more than 100 kilograms are all tilapia, and in the 1980s Lao Wang often fished in the area is mostly 4 large fish.
Why are tilapia so rampant? The reasons are manifold. Tilapia eats miscellaneous food, eating both phytoplankton, organic detritus, mosquito larvae, but also eating small trash fish, carrion, other fish may be hungry, but it can eat enough, there is enough energy to breed.
Adult tilapia in one breeding season produces about 1,000 eggs, the vast majority of which survive. What's more, tilapia grows rapidly, grows to 150-250 grams in 4 months with adequate food, and reaches sexual maturity.
As a result, after 20 or 30 years of breeding and spreading, tilapia has now spread throughout the East River, West River, North River and Pearl River Estuary, and tilapia in some sections of the river accounts for 1/4 of the total number, and every 4 fish species must be tilapia. Tilapia occupy the resources of the water body, leaving naturally less space for other fish, either hungry and skinny, or disappear.
The foreign fish in the Pearl River are chaotic into a pot of porridge
Exotic fish species in the Pearl River are generally more "dashing" than indigenous fish, but they are also more "chaotic" and are currently in a stage of fierce confrontation. For example, tilapia and scavengers, both fish eat fish eggs, and when tilapia spawns, the scavengers are on the sidelines until they are eaten! So what to do? It depends on who breeds more!
In addition, scavengers also eat the eggs of indigenous fish and other exotic fish in the Pearl River, which may be a fatal blow to the indigenous fish that are already few, and may also cause the alien fish that have just established a colony in the Pearl River to disappear.
And that's not all, in addition to the cannibalization of foreign fish, the competition for foraging is also particularly fierce. For example, tilapia and wheat carp, wheat carp lay more than 100,000 eggs at a time, and eat miscellaneous, fast growth, the year of raw juvenile fish grew to more than 300 grams, so tilapia and wheat carp also in the Pearl River fierce competition. In 2019, fisheries researchers collected fish samples in parts of the Pearl River and caught a total of 5,867 fish, of which 927 were exotic species. Of the exotic species, 360 are tilapia and 407 are wheat carp.
That is to say, the foreign fish get along so "harmoniously" with each other, and the structure of the Pearl River fish may change again.
Original: Blog post