Not only pufferfish are toxic. Some common fish that you may eat also contain toxins, such as herring, tuna, eel, and sardines…
Fish with Toxic Spines
Many types of fish have toxins in their protective spines. They possess sharp, pointed spines on their dorsal, ventral, pectoral fins, and gills, living mostly in the sea. Some live in freshwater, such as the Chinese soft-shelled turtle (also known as Chinese carp) — which has 12 unequal spines on its dorsal fin, with the 4th, 5th, and 6th being the longest. When these spines puncture the body, the affected area swells, becomes inflamed, and painful, and the entire body may experience fever. Complications can be severe when toxins and mucus secreted by the fish enter the body through the puncture wound.
Fish with Toxic Glands (with ducts or without ducts leading to the spines in the fins).
This type of fish inhabits both offshore and nearshore areas, blending in with the seabed. Examples include sharks, hammerhead sharks, tiger sharks, thorny sharks, moray eels, catfish, and stingrays. They have numerous toxic spines on their dorsal, ventral, anal, and caudal fins, as well as strong, sharp teeth. When a stingray’s tail strikes another animal, the spine may break, and a new spine will grow in its place. The toxin affects the nervous and cardiovascular systems, causing muscle paralysis and lowering blood pressure. The toxins secreted from the dorsal spines are less potent than those from the spines located at the fish’s gills.
Fish with Toxic Eggs
Many cases of fish poisoning resulting in death are due to consuming toxic fish eggs. Fish with toxic eggs often have small fins (such as hammerhead sharks and pufferfish…). Various types of fish have toxins in their reproductive organs, including spotted pufferfish, hedgehog pufferfish, flatfish, herring, eel, and sardines. The toxins in pufferfish and hammerhead shark eggs are very stable against heat and chemicals. In our country, there have been numerous severe poisoning cases from eating pufferfish eggs, with some cases leading to the death of entire families. The toxins from the eggs can circulate in the fish’s blood, making the serum in the fish’s blood highly toxic.
Along our coastline, several types of fish commonly have toxic eggs:
– **Pufferfish:** Slim body, large head, tapering towards the tail, large teeth, finless body, but has leopard-like skin (except on the belly).
– **Herring:** Features long, soft spines on the dorsal fin (spotted herring), or very straight lateral lines. From the mouth to the tail, it has sharp fins, no teeth, delicious flesh, but the eggs and liver are highly toxic. During the breeding season, toxins are also present in the fish’s gills, so it is absolutely forbidden to eat this fish during spawning season.
– **River Eel and Sea Eel:** This group is primarily toxic in blood and serum. They have pointed heads, pectoral fins, no ventral fins, very sharp fins, small sharp teeth, and a tongue. They are abundant in tropical regions, both in rivers and seas, with some species weighing up to 2 kg.
Fish Poisoned by Parasitic Microorganisms
Sturgeons, salmon, and other fish often have clostridium botulinum bacteria on their bodies. It is impossible to distinguish infected fish from others, while poisoning due to botulinum is often fatal. Particularly, fish in tropical regions are very susceptible to microorganisms that invade and thrive on the mucus secreted by the fish. Microorganisms proliferate even more rapidly when the fish dies, coinciding with the highest secretion of mucus. Thus, hygiene during cooking becomes critically important, especially when consuming seafood.
Fish with Undefined Toxicity
In many tropical countries, some fish possess toxins with lethal doses that are very small, and the nature of the toxins has yet to be studied. A representative example is tuna, which is abundant in our country. These large fish can grow up to 4-5 meters in length and weigh several hundred kilograms. They have pointed heads, slender bodies, with 14 long, hard dorsal spines, the second being the longest, gradually decreasing to the 14th spine. Tuna are dark blue on the back and silvery white on the belly. Tuna toxicity results from microorganisms that decompose the amino acid histidine into histamine. Individuals accustomed to consuming seafood often experience only mild allergic reactions when eating tuna.
Some river fish also contain toxins in their flesh and internal organs (liver, bile) due to their diet (toxic vegetables, seaweeds). For example, fish that consume the seeds of the Strychnos nux-vomica tree along riverbanks can cause poisoning in those who eat them. There have also been cases of people suffering from allergies and poisoning from consuming improperly processed, dried seafood.
To avoid fish poisoning, it is essential to identify the fish before cleaning and cooking them thoroughly. For unfamiliar fish, all internal organs should be removed. If in doubt, it is advisable to feed them to dogs or cats for testing first. If any signs of poisoning appear, the victim must be promptly taken to a medical facility for immediate treatment. While waiting for emergency transport, efforts should be made to induce vomiting to expel the toxins from the body.
