Are Groupers Poisonous?

Groupers can be poisonous and can cause various health risks to people who consume them. This article will take a detailed look at why some groupers are poisonous and how they can affect human health.

How are groupers poisonous?

Groupers are a bunch of gentle giants from the Epinephelinae subfamily who reside in the mangrove and tropical reef waters. They can be poisonous for two reasons that are based on what they eat

Ciguatera poisoning

The large and tropical predatory reef fishes, if consumed, can cause a form of food poisoning called the ciguatera fish poisoning. These fish include barracudas, moray eel, sturgeon, sea bass, red snapper, amberjack, mackerel, parrotfish, surgeonfish, triggerfish, as well as groupers.

All of these are reef fish from the tropical and subtropical waters of different places. Locations like the Pacific Ocean, West Indies, and the Indian Ocean pose the greatest threat. In the US, cases of ciguatera fish poisoning have been reported in Hawaii, Guam, Puerto Rico, U.S. Virgin Islands, and Florida. There have also been some reports from the eastern seaboard of the US.

Many of these tropical reef locations are the homes to grouper fish. It is to be noted that the reports related to groupers were from back when people were still legally allowed to harvest, catch, and eat groupers. Now it is banned in many states, but it’s still important to be aware of the fish poisoning that can be caused by it for areas where it’s still allowed.

According to health officials, ciguatera fish poisoning can be caused by more than 400 species of fish, especially reef fish. According to the U.S. Centers for Disease Control and Prevention, these fish contain toxins that are produced due to the consumption of a marine algae called Gambierdiscus toxicus, a big part of their diets.

Mercury poisoning

Groupers are bottom feeders, which means that their food source lies at the bottom of their habitat. Since they are carnivorous, they prey on smaller fishes that hang around on the bottom portion of the water bodies, as well.

The bottom part of every water body has fewer concentrations of oxygen but more mercury. Mercury is naturally produced in the environment, but due to industrial pollution, the amount has increased, and since mercury dissolves easily in water, it accumulates at the bottom of the water bodies due to its higher density.

Due to fewer oxygen concentrations, this mercury combines with carbon to become methylmercury at the bottom. This is a highly toxic compound, and the bottom-dwelling fish consume the methylmercury particles from the floor.

Groupers, as bottom feeders, eat these fish, and thus the particles enter their bodies. They also consume more of these, and hence the amount of mercury in their bodies is very high. Most bottom-dwelling and bottom-feeding fishes are poisonous and consuming them can cause mercury poisoning.

Why can it bad to eat grouper?

It might be tempting to have a taste of these fleshy groupers, but at what cost? A single grouper fish might be able to provide for a small family’s months’ worth of dinner, but not without leaving the dangerous side effects of ciguatera fish poison and mercury.

Ciguatera fish poisoning is a serious type of food poisoning having adverse effects. Nausea, vomiting, diarrhea, and such typical symptoms of normal food poisoning will occur for a minor case, but the symptoms can get worse, and the neurological side effects will begin to appear.

  • Difficulty walking
  • Bodily weakness
  • Reverse temperature sensation, as in cold things can feel hot while hot things will feel cold.
  • Toothache
  • Muscle pains in different places of the body
  • Dizziness
  • The irregular rhythm of the heart
  • Low blood pressure (worse if the patient already had it before consumption)

According to the CDC, ciguatera poisoning symptoms typically resolve within several days, but in many cases, it might last up to four weeks or even a few months. In some cases, symptoms have lasted up to a year. Consult a doctor for the diagnosis. There is no specific cure for this.

Mercury poisoning, on the other hand, can have even worse effects. Symptoms include-

  • Nervousness or anxiety
  • Irritability or mood changes
  • Numbness
  • Changes in vision, hearing, or speech
  • Memory problems
  • Lack of motor skills or feeling uncoordinated
  • inability to feel in the hands, face, or other areas
  • Depression
  • Physical tremors
  • Difficulty walking or standing straight
  • Muscle weakness
  • Metallic taste in the mouth
  • Nausea and vomiting
  • Difficulty breathing

Since grouper fish, in particular, has an extremely high concentration of mercury in their body, eating even a small amount of it can start showing the side effects. These include erectile dysfunction, motor skills impairment, neurological damage, cardiovascular risks, problems in the renal system, deformity in the fetus (if the patient was a pregnant person), and such.

Is catching grouper fish banned?

Yes, goliath grouper fishing has been made illegal in countries where groupers are available. However, the ban on fishing might be lifted in the next few years, depending on whether or not this species is still endangered or not.

Goliath groupers live very long, but they don’t reproduce much in their lifetime, and this made them prone to overfishing and soon pushed them to the category of endangered species, but groupers are important parts of the tropical reef ecosystem, so their extinction will have a very negative impact.

That’s why many places like Florida and Australia have illegalized catching goliath grouper for a few years. In fact, goliaths almost went extinct in Florida back in the 1980s, which is why the Florida Fish & Wildlife Conservation Commission placed a ban that is still somewhat going on to this day but with more regulation.

Basically, the Florida Fish and Wildlife Conservation Commission approved on Oct. 6, 2021, a proposal to allow the recreational harvest of 200 goliaths per year from March to May. This might change, and a full ban might be imposed if the situation reverts to how it was thirty years ago. Other types of groupers can be caught because there are not bans on them.


It’s clear that some grouper can be poisonous, and they could be harmful to the human body.


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