Poisoned by fish
There are a huge number of fish on earth, and at least 1,000 different species that are poisonous or venomous. Fish can poison or envenom humans or other animals, either when eaten, or by stinging. Often the venom is used as a defence against predators, but it can also be a way of killing prey. Some venomous and poisonous fish are brightly coloured or have long, visible fin rays, to warn predators in advance.
Eating a poisonous fish can make you feel nauseous, or cause cramps, headaches, diarrhoea, dizziness, vision changes and heart problems. In some cases, you may suffocate, through paralysis of the respiratory system. If you are stung by a venomous fish, you may experience similar symptoms, and it is common for circulation to drop so much that blood is no longer pumped around normally. This is called medical shock. A sting from a venomous fish can be incredibly painful, and in some cases even fatal!
Stingrays are a group of cartilaginous fish with several different species. They have a venomous stinger on the tail, as a defense. It hurts terribly to be stung, and you can get very sick with swelling and vomiting. It is rare for people to die from being stung by a stingray, but it has happened.
Photo: James-St.-John-CC-BY
The body of the pufferfish contains poison. This makes them harmful to eat, and some species are even deadly for us humans. In Japan, it is considered a delicacy to eat pufferfish, it is called "fugu". Only specially trained chefs are allowed to prepare this dish.
The spotted trunkfish lives in coral reefs in Asia, and it secretes a toxin from glands on its back. The poison is only harmful if you eat the fish.
Photo: Betty-Wills-CC-BY-SA
Tropical fish that sting
Stonefish belong to the Scorpaenidae family. The stonefish is highly venomous, and lives in the tropical parts of the Pacific and Indian Oceans. It has 13 venomous spines on its back with which it stings. It is one of the most venomous fish on earth, and several people have died from accidentally stepping on it. The stonefish often lies on the bottom, and has a well-developed camouflage that makes it difficult to detect.
The red lionfish has long fins and fin rays that protrude from both its sides and back. It inhabits coral reefs. The tips of the dorsal fin rays are venomous. The sting from the red lionfish is rarely fatal to humans, but it carries a neurotoxin that causes severe pain, vomiting and breathing problems, and it will require medical attention.
The stonefish has 13 spines on its back, which are connected to venom glands inside the body. The venom attacks the blood, nerves and heart of the victim, causing shock, paralysis and cell death. It is one of the world's most venomous fish!
Photo: Bernard-DUPONT-CC-BY-SA
Lionfish have hollow fin rays in their dorsal fin, which act as syringes. All lionfish are venomous, but it is very rare for humans to die from the venom. However, it is terribly painful to step on, and get stung by, a lionfish.
Photo: Jens-Petersen-CC-BY
The greater weever is a species that is found in Swedish waters. It has venomous spines. It is not fatal to be stung by a greater weever, but it leads to swelling, and you can suffer from fever, nausea, headache and dizziness. It is important to seek medical attention if you get stung by the greater weever.
Photo: Helge-Busch-Paulick-CC-BY-SA
The viper of the sea and Sweden’s only venomous fish
The greater weever is the only fish species in Swedish waters that has a dangerous toxin. It has venomous spines that are located partly on the gills and partly on the front dorsal fin. You can accidentally get stung by it when swimming, or if you attempt releasing it from a fishing net. The greater weever can be found along the west coast of Sweden down to Öresund. A sting causes severe inflammation with pain, swelling and numbness, and you will need to seek medical attention. A relative of the greater weever is called lesser weever. It is sometimes called ”the viper of the sea” as it is the most venomous fish species in Europe. The lesser weever lives along the coast of Denmark and in large parts of the Atlantic, Black and Mediterranean Seas.