Harehead and lionfish: How dangerous are bathers

With his presence now on seas of South Euboea and Eastern Attica to be confirmed, the harefish has been spotted by fishermen in several areas such as Palaia Fokaia, Saronida, Varkiza, Bourtzi, Lefkadi and Eretria.

Its arrival from its beaches Crete upwards creates reasonable concern and questions. What is the interaction of this alien species with humans in the water and what should bathers do in case they “encounter” it?

O Dimitris Klaudatosassociate professor in Fisheries at the Department of Agriculture, Ichthyology & Aquatic Environment of the University of Thessaly, specializing in alien species, analyzes in “K” what we need to know about the redhead and its peculiarities while classifying the alien species of the Mediterranean based on their degree of danger to humans.

How dangerous is the lagocephala really?

Mr. Claudatos characterizes the lagocephalus (Lagocephalus sceleratus) as one of the most problematic Lessepsian species in the Mediterranean, both ecologically and as a matter of public health. As he states, the danger it poses to humans is twofold. On the one hand toxicological, through accidental consumption, on the other mechanical, as its strong beak-like jaw can cause serious bites. “Today it is now established as a serious threat to marine ecosystems, fisheries and public health throughout the Mediterranean,” he emphasizes.

Poisoning can be rapidly fatal, as there is no antidote, and the lethal dose for humans is estimated to be only 1–2 mg.

What is tetrodotoxin and what does it do to humans?

Harehead contains a very strong neurotoxin, of a non-protein nature, which is heat resistant, i.e. it is not destroyed by cooking and is mainly concentrated in the liver, genitals, intestine and skin of the fish. “Once the hare’s head is consumed, symptoms of poisoning, such as perioral numbness, paresthesias, weakness and ataxia, usually appear within the first hour and can progress to respiratory paralysis. Poisoning can be rapidly fatal, as there is no antidote, and the lethal dose for humans is estimated to be only 1–2 mg. The treatment is exclusively supportive, mainly with mechanical ventilation”, notes Mr. Claudatos.

Am I in danger of being poisoned even by contact?

The answer is no, touching the skin of the fish does not involve poisoning. The risk exists only by eating the fish, as the concentration of the neurotoxin in the skin of the fish is low, and touching it is not the same as eating it. Therefore, touching a dead or live porcupine does not carry the above risks.

Have poisonings or deaths been recorded in the Mediterranean and in Greece?

“Yes. A recent study in the journal Biology recorded, for the period 2004–2023, a total of 198 incidents in the Eastern Mediterranean, including 28 attacks (bites) on humans and 27 deaths from consumption of sea bream. In Greece, according to published data, no deaths have yet been recorded, however incidents of bites to bathers have been reported,” says Mr. Claudatos.

If I am a bather, am I at risk?

The professor notes that the risk concerns both cases, as in addition to the deadly toxicity, there is also a direct mechanical risk in the water. However, he points out that the harefish, like all fish, does not attack people on its own. The most common reason a fish, such as a bullhead, might bite a bather is misidentifying an object as food. For example, shiny objects such as jewelry or metal accessories may attract the animal’s interest and be perceived as potential prey.

In several cases in the Mediterranean, bites to people in the sea have been recorded, some of which have resulted in serious injuries or even amputation of fingers.

From scientific research, the expert notes that in several cases in the Mediterranean, bites have been recorded to people in the sea, some of which led to serious injuries or even finger amputations. Bites occur more often during the summer months, due to increased human presence in the water, while poisoning by consumption is mainly observed in the winter.

How do we recognize the lagocephalus?

The characteristics of the goby are quite distinctive as it has a spindle-shaped body, a silvery belly, a dark back, a strong silvery lateral line, dark spots along the back, the absence of scales on much of the body and, most importantly, the distinctive “beak” formed by four fused teeth. In addition, it has the ability to inflate when threatened. It does not resemble any commercial native species, so in all cases of doubt it is not consumed and disposed of with great care.

@jim_ryomen First time I saw such a big hare’s head #hareheads ♬ original sound – jim ryomen

Is the porcupine the only dangerous alien species?

Mr. Claudatos notes that although it is the most notorious alien species, it is not the only one. In the same category of toxicity belong other Lessepsian species of lagocephalus, such as Lagocephalus spadiceus and L. suezensis, which also show dangerous levels of tetrodotoxin. In addition to these, there are species with a mechanical or poisonous risk, such as lionfish and catfish.

Which alien species can harm humans?

The main species that pose a risk of injury are:

• The lionfish (Pterois miles), bearing poisonous thorns.
• The striped catfish (Plotosus lineatus), with very poisonous spines on the fins and particularly painful, dangerous bites.
• The hare headsboth due to bites and toxicity.
• As well as the species of the Siganidae family, such as wild salpa or German (Siganus rivulatus) and o black german or curcuma (Siganus luridus), which, although edible, have slightly poisonous spines that cause a painful but non-lethal sting.

Lionfish: How dangerous are its spines?

According to the expert, the lionfish has poisonous spines on its dorsal, ventral and dorsal fins. The venom is proteinaceous in nature and causes acute pain and inflammation, noticeably more intense compared to the stings of wild salps, while more rarely more serious reactions can occur. “It is not an aggressive species, the danger arises mainly if someone accidentally touches or steps on it. First aid is to remove any spines with tweezers, disinfect the area and immediately immerse the wound in as hot water as the victim can tolerate for 30 to 90 minutes. Since the poison is proteinaceous in nature, the high temperature neutralizes it, but not exceeding about 50 °C. In any case, a visit to a medical center is recommended,” he says.

What other alien species can cause injuries?

In addition to the harehead, the professor singles out the blue crab (Callinectes sapidus), which has extremely strong and sharp pincers, capable of causing deep cuts to fishermen when unhooking or to bathers who step on it. Also the fistularia or trumpet fish (Fistularia commersonii) does not attack, but its long, hard and pointed snout can accidentally injure swimmers or divers in conditions of low visibility.

What are the alien species that scientists are following most closely in the Greek seas today and why?

According to Mr. Claudatos, the focus of scientific monitoring is on the sea bass, due to the risks to public health, the damage to the fishery and the ecological pressure it exerts. There is also the lionfish, as a poisonous species and a voracious predator of fry that is spreading to the north, as well as the trumpet (Fistularia commersonii) and foreign mullets (Upeneus moluccensis, U. pori, Parupeneus forsskali), which feed on the fry of native fish or compete with local species for food and space.

Other species are the nomadic jellyfish (Rhopilema nomadica), due to the mass appearances and stings on bathers in the eastern Mediterranean and the blue crabs (Callinectes sapidus, Portunus segnis), due to the effects on lagoons and fisheries. “The reason for the intensive monitoring is that the ratio of alien to native species in the catch is increasing significantly, while at the same time there is a decrease in the total number of species in areas where invasive species prevail. The main drivers of this change are climate change and overfishing, which disrupt the balance and favor the establishment of new species,” he notes.

We can classify alien species based on the danger they pose to humans. Which would you put at the top of the list and why?

“Considering the seriousness of the consequence, a reasonable hierarchy places the harehead at the top, as the only species that combines potentially fatal toxicity (tetrodotoxin, without antidote) with a mechanical risk of bite, and indeed with already recorded deaths in the Eastern Mediterranean,” says the professor.

In second place he puts the lionfish, with its poisonous spines that cause very painful bites, but rarely life-threatening. Next is the striped catfish, with powerful poisonous spines and extremely painful wounds. In fourth place is the nomadic jellyfish, due to its painful stings and mass appearances that affect many bathers at the same time. Finally, the other species, such as the blue crab, cause mainly local mechanical injuries.

“In my view, at the top are those that can cause death, followed by venomous species with severe pain but low mortality, and at the bottom are those that cause mostly local injury. However, it is worth noting that the actual risk also depends on the level of exposure. The hakefish mainly concerns fishermen and consumers, while the jellyfish and lionfish concern more bathers and divers”, concludes Mr. Claudatos.