Meet other fish that threaten nature

Harmless at first glance, goldfish have become one of the marine species that most threatens ecosystems. Originating in countries such as China and Japan, they began to be sold in stores around the world to be created in aquariums. The problem came when they started to be released into the wild.

The 5 to 10 cm small fish proliferate quickly and now reach at least 30 cm in length.

According to a publication in Scientific American, about 20,000 goldfish were found living in a medium-sized lake in inland Canada. Some of them weighed up to 3 kg, an unusual trait for the species.

The anomaly may be associated with the presence of these animals in artificial lakes with high levels of contamination.

Able to adapt to different habitats, goldfish are also harmful to the quality of the water where they live, as they stir up sediment at the bottom of lakes, releasing phosphorus into the water, and also uproot plants while feeding.

In late 2020, reports The Guardian, authorities in Minnesota (USA) removed at least 50,000 goldfish from local waters.

See below for other fish species that threaten ecosystems.



Image: Playback/Google+

Venomous and predatory, the lionfish has become a new threat to the marine ecosystem of Fernando de Noronha (PE). It feeds on other fish, attacking them through the poison present in its spines. In case of contact with humans, the toxins can cause pain, fever and convulsions. It can live up to 100 meters deep and preferably far from the beach, sheltered in corals.

Capturing it is often a complicated task. Since it lives in deep water, this fish is basically only reached by diving to the bottom of the sea. They are rarely caught in fishing nets.

According to scientists from Oregon State University (USA), the presence of this fish in places where it is not native has the potential to be one of the most ecologically harmful marine invasions ever observed.


Toothed pufferfish named Goldie, from England - Unsplash/Reproduction - Unsplash/Reproduction


Image: Unsplash/Playback

Known for its ability to inflate when threatened, the puffer fish is found in warm and temperate regions around the world, especially at sea.

Poisonous, the puffer fish keeps a highly toxic substance, tetraodontoxin, which is concentrated in its internal organs. If consumed inappropriately, it can lead to death.


Known as the vampire fish, the candiru is a parasitic fish up to six inches and eel-shaped, making it almost invisible in the water.  It enters the body of victims through the urethra, where it arrives following the trail of urine.  Inside the victim's body, the candiru feeds on blood and can only be removed through surgery - Jonas Alves/Instituto Mamirauá/Disclosure - Jonas Alves/Instituto Mamirauá/Disclosure


Image: Jonas Alves/Mamirauá Institute/Disclosure

Also called catfish, the candiru (Vandellia cirrosa) is found in the Amazon River region. It has a translucent appearance, resembles an eel and usually grows to only 2.5 cm.

Candiru, however, can attack humans. When this happens, it enters the bathers’ urethra, and once, in the passage of the canal, it raises the short spines on its gill covers, causing inflammation, hemorrhage, and even death of the victim.

moray eel

5. Green moray eel.  Also found in Brazil, it can reach four meters in length.  - Wikipedia - Wikipedia

green moray eel

Image: Wikipedia

One of the most dangerous fish in the world, the moray eel is found in all tropical and subtropical seas, where they live in shallow water between reefs and rocks and hide in crevices. Wide-mouthed and jawed fish with strong, sharp teeth, it can attack humans when disturbed.

Moray eels serve as food in some regions of the world, but their flesh can be toxic and cause illness or even death.

tiger fish

25. Tigerfish - Reproduction/I Love Animals - Reproduction/I Love Animals

tiger fish

Image: Reproduction/I Love Animals

They are known for fighting when caught and also for their fiercely predatory habits and appearance. Depending on the species, it may have one or several dark, longitudinal stripes. It is a carnivorous fish, which resembles a salmon, and has dagger-shaped teeth, which protrude when the mouth is closed.

The three-striped tigerfish is a common species, vertically striped about 30 cm long. It has sharp spines on its gill covers, which can injure a careless handler.


28. Piranha: Devil Fish - Reproduction/jacobsschool - Reproduction/jacobsschool


Image: Reproduction/jacobsschool

Piranhas have a deep body and large head, with a strong jaw and sharp, triangular teeth that meet in a scissor-like bite.

The most dangerous of the species is the red piranha, which has stronger jaws and sharper teeth. It lives in shallow waters and is known to hunt in groups that can reach over 100 piranhas.

Piranhas can “smell” a drop of blood in 200 liters of water. They also perceive the vibrations of the movements of injured animals in their aquatic environment. This is how they locate their prey.

Sometimes, piranhas stay close to their victims, until they get used to their presence, and then attack them. Your teeth are not made for chewing, but for cutting and swallowing. So when a hungry school of fish attacks, the prey carcass is quickly devoured.

In Brazil, the piranha-mapará species is commonly found (in the Orinoco river basin and in the tributaries of the lower Amazon) and the yellow piranha, a species native to the São Francisco river. Both are dangerous to humans.

stone fish

19. Stonefish - Reproduction/Haiku Deck - Reproduction/Haiku Deck

stone fish

Image: Playback/Haiku Deck

Stonefish are venomous and camouflage themselves in coral reefs to hunt and hide from predators. The venom expelled by the 13 spines of the stonefish’s scales can kill a human being in two hours if help is not immediate.

Stonefish usually rest on the ocean floor, not moving, blending in almost exactly with their environment in shape and color, and as a result, they turn out to be dangerous. When stepped on, it can inject amounts of venom through grooves in its dorsal fin spines.

Electric fish

The electric fish Poraquê - Reproduction - Reproduction

Electric fish

Image: Reproduction

Common in the Brazilian Amazon and popularly known as poraquê (Electrophorus electricus), the electric fish produces a powerful electric shock capable of killing a horse with a shock of more than 500 volts. According to several studies, this fish is capable of producing up to 1500 volts.

When electrocuted, the prey is stunned long enough to be sucked through the mouth directly into the animal’s stomach. Sometimes the fish is not concerned with stunning the prey, but with swallowing it as quickly as possible.

manta ray

12.jun.2015 - The manta ray nicknamed "mangini" was discovered in diving last Tuesday (9) and its photos released on Friday (12).  The five-meter lane was located on the south coast of São Paulo in a region called Dom Pedro II.  Three other rays of the same size were found in the region, after fishermen came into contact with the Mantas do Brasil project.  The animals have already been cataloged in the Banco Brasileiro de Mantas (BBM).  Manta ray fishing has been prohibited since 2013 because it is an endangered species - Leo Francini/Mantas do Brasil - Leo Francini/Mantas do Brasil

manta ray

Image: Leo Francini/Mantas do Brasil

The manta ray has a short, whitish tail and has fleshy pectoral fins that are large enough to look like wings.

They have venom in the spines located on the back of the tail. Injuries often occur when a person steps on a stingray (which is often buried in the sand) while walking in shallow marine waters. It launches its tail and drives the spikes into the person’s foot or leg, releasing the venom.

White shark

white shark - Reuters - Reuters
Image: Reuters

The great white shark (Charcharodon carcharias) is reputed to be the fiercest and most aggressive of all sharks. In areas where they are more common, such as the coast of the United States and Mexico, southern Africa and the Mediterranean Sea, they are responsible for some attacks on swimmers, divers, surfers and even small boats.

The white shark attacks its victim with a single bite and then retreats. He rarely returns for a second bite.

In addition to the striking silhouette, what most terrifies people are the three thousand triangular teeth, serrated and very sharp, 7.5 centimeters in height, inserted in the jaws in rows slightly inclined inwards. This formidable set can exert the force of three tons per square centimeter in one bite.

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