The lionfishes (also called turkeyfishes or zebrafishes) are certainly some of the most recognized of the marine fishes, likely second only to the percula clownfish. Yet, these members of the Family Scorpaenidae are well known around the world not only for their looks, but for their ability to strike an unlucky victim with venom-delivering spines, as well. The fact that lionfishes are collectively one of the most popular aquarium-kept fishes makes the potential for hobbyists to receive such injuries very likely. Thus, it is a good idea to be aware of the common cause and effects of a sting and the appropriate first aid and treatment for such. Fortunately, while stories of lionfish stings having horrible effects (including death) abound, and are even heard in Hollywood movies, the truth is far less exciting. As it turns out, a mortal sting is much more likely to come from one of the lionfish's less conspicuous cousins.

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Figure 1. Pterois volitans - One of the most recognized and popular fishes in the marine aquarium hobby.

The Fishes

While all of the fishes that comprise the Family Scorpaenidae are indeed venomous, the members of the family can be split up into three general groups, each of which deliver venom of differing quantity and potency. Lionfishes (ex. Pterois spp.) are known for typically having long, relatively slender spines, and they also have the smallest venom glands and produce the weakest venom. The scorpionfishes (ex. Scorpaena spp.) have shorter, but sturdier spines and larger venom glands compared to the lionfishes, and thus have the potential to deliver a more potent sting. However, it is the stonefishes (ex. Synanceia spp.) which are the truly hard-hitters. Armed with even shorter and stronger spines, they have the largest venom glands, and can deliver a much larger dose of far more powerful venom to a victim.

Figure 2. Clearly visible are the venom-delivering dorsal spines of this P. volitans.

Lionfishes can vary in adult size from only 4" (ex. Dendrochirus biocellatus - the Fu Manchu lionfish) up to 15" (ex. Pterois volitans - the Volitan lionfish), and are voracious predators that feed on everything from small shrimps to surprisingly large fishes. They typically have 12 to 13 elongated dorsal spines, and also have 2 pelvic spines and 3 anal spines, all of which have a pair of venom glands at each of their bases. However, the fan-like array of pectoral fins, which may appear superficially the same as the dorsal fins in structure, are not equipped with these glands.

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While the ornate, free-swimming lionfishes are typically easy to spot, the scorpionfishes and stonefishes typically are not. These fishes tend to have well-camouflaged bodies and spend much if not all of their time sitting motionless on the seafloor where they feed by ambush, as unwary prey items get a bit too close. With this in mind, it should be no surprise that essentially all envenomations by scorpionfishes and stonefishes come by way of unintentionally stepping on one that has eluded visual detection, rather than as the result of an aggressive attack. Fortunately, both of these types of scorpaenids are rarely, if ever, offered to hobbyists, and I don't know of anyone that walks around in their aquarium either. So, these two groups of fishes are not a major concern to aquarists.

The Envenomation

Stings from lionfishes are a defensive response, typically to being cornered or harassed in some way, with the dorsal spines being the predominant weapon. Lionfishes can charge at an adversary at surprising speed considering their less-than-hydrodynamic appearance, and wield the dorsal spines like so many tiny lances in a joust. This happens most often during tank maintenance, when the aquarist's attention may move away from the fish and to the task at hand. While most fishes will typically move away from a scrubbing arm, the lionfishes have a habit of occasionally moving away - just enough to get a running start back at the arm. I have been stung myself in this way, and I'll tell you that it happened in the blink of an eye. My advice is to watch what you are doing and don't assume that a fish you've had for a while has somehow turned "tame", as the 12" individual that stung me had been in an aquarium under my care for at least two years without incident. For whatever reason, it was "spooked" that day, and reminded me that I shouldn't be so careless as to ignore it. Of course, the other common way to get stung is to attempt to handle a lionfish during transportation, introduction, or relocation, with the end result being the same.

The mechanism of the sting is actually rather simple. Each spine is covered with a sheath-like integumen from tip to base, which is compressed down the spine when the spine is thrust into a victim's flesh. The venom glands are positioned at the base of the spine, and upon compression of the integumen, they are basically squeezed from above and thus release their product. The venom then travels through thin grooves in the spine and is delivered into the puncture wound created by the spine. As I understand it, the harder the strike, the deeper the wound, the more compression, and the more venom injected. Hence, light strikes can be far less injurious than hard ones. The venom delivered is variable in toxicity among types of lionfishes. However, in all species the venom produced is comprised of thermolabile proteins which, as the name suggests, are sensitive to heat.

Another aspect of a strike is the potential to have a spine(s) broken off in the victim's flesh. Recall that the spines of the lionfishes are relatively long and thin, and sections can be snapped off should the victim jerk away from an attacking fish at the moment of insertion. While the venom may initially be the only concern, a piece of spine left in a wound may actually be far more detrimental to a victim's health in the long run.

The Effects

Again, while stories of death by lionfish are common, it has been impossible for me to find a single documented case of such after an extensive search of medical literature. Other authors have reported the same results. This does not mean that it has never happened, but it implies that death by lionfish is exceptionally rare or unrecognized. It may in fact be limited only to those victims that might display some sort of allergic reaction, or to those that suffer from a fatal infection related to the wound.

Conversely, in the vast majority of cases, the predominant effects of a sting are nothing more than severe pain and swelling (edema) in the area around the puncture. Some victims have experienced systematic responses such as nausea, dizziness, muscle weakness, shortness of breath, hypotension, and headache brought on by the venom, or as a reaction to the level of pain, or both, but that's about it. In the worst of cases when medical treatment has been administered, some blistering and/or tissue loss (necrosis) has been experienced in the wound area, but this is very uncommon.

In a series of 101 documented cases of captive lionfish envenomations in the US, the following effects were reported (Gallagher, 2001):
     92% of patients experienced local pain
     60% of patients experienced edema
     13% of patients experienced systematic symptoms
     1% of patients experienced tissue necrosis
     0% of patients experienced death

In another study of 45 documented cases of captive lionfish envenomations reported to the San Francisco Poison Control Center over a 5 year span, the following effects were reported (Kizer, et al, 1985):
     100% of patients experienced local pain
     22% of patients experienced pain extending through the affected extremity
     13% of patients experienced systemic symptoms
     0% of patients experienced death

So, you should be convinced at this point that the odds of being seriously injured by a lionfish, while not null, are certainly slim if the wound is treated properly.

The Responses

There are several things to do if stung by a lionfish, one of which is getting professional help. I realize I've just pointed out that the chances of receiving a serious injury are slim, but that's if a sting is treated promptly and properly. Avoiding professional help, or neglecting such an injury, can be very painful and can lead to real trouble. Applying first aid at home can help to relieve the pain almost immediately, but a trip to the emergency room is strongly advised.

As far as first aid goes, you should check to see if there are any obvious pieces of spine left in wound. If any are present, and can be easily removed, do so with great care. Oftentimes it may be too painful an ordeal to remove pieces yourself, and you may need to wait until a medical professional can take care of it. The pieces are best removed using tweezers and a microscope anyway, and it's likely that if you get stung, it will happen to your dominant hand. Left-handed home surgery (or right for the lefties) sounds bad to me - something to take into consideration. Special care should also be taken if a piece is imbedded near a larger blood vessel, a joint, or a major nerve, etc., in which case you can compound the problem by attempting to do it yourself.

In the event that the wound bleeds, apply direct pressure to help stop the flow. But, you may have to forego this procedure if you believe you may have a piece of spine left in the wound. Better to bleed a bit than to unintentionally force a piece of spine further into your flesh.

The next step is hot-water therapy. The venom is broken down very effectively by exposure to heat, and you can therefore soak or bathe the injured body part in water that is as hot as you can stand. This is normally around 110° to 114° F, and should not be any hotter as you'll risk scalding yourself and making matters worse.

Of course, the sooner you can get to a hospital the better, and upon arrival it is important to report exactly what kind of fish has stung you. You should not assume that every doctor knows what a lionfish is - so explain if necessary. Once under their care, you will likely receive a hot-water treatment for 30 to 90 minutes, and may get a shot of anesthetic if the pain is still severe. Some doctors have suggested the use of a long-lasting painkiller like bupivicaine to ease the pain, as it can be used to deaden a wound area for hours. However, in the study of 101 cases summarized above, 97% of patients were relieved of pain by using the hot-water treatment only. Either way, once the initial treatment is complete, the wound should be elevated if needed to help reduce any swelling.

While you may play surgeon and try to remove any pieces of spine yourself, it is absolutely imperative to make sure that any and all material is cleared from the wound. Thus, it is highly recommended that the area be thoroughly checked using standard X-ray techniques, ultrasound, or even a CT scan or MRI scan. While this may seem excessive, keep in mind that the subsequent infection of a wound can oftentimes be far worse than the wound itself, and that leaving even a tiny piece of a fish under the skin is a good way to get one.

Be aware that if you should get an infection whose effects spread into other body parts and/or systems (bacterial sepsis), you stand a good chance of dying even if the sting itself was not life-threatening. Therefore, in all cases where a skin-breaking wound is caused by a marine organism, tetanus prophylaxis (like a shot) is required if you are not already up to date. It is well documented that tetanus has caused many deaths following marine organism-related penetrating wounds. Likewise, numerous other infections can also occur in conjunction with such wounds, including those caused by Vibrio spp.

I can't emphasize enough - be mindful of the possibility of the after-effects of a sting. Bad stuff! Because the potential for these complications is so high, doctors may also use various antibiotics as part of treatment. This is especially true if an infection appears some time after the initial injury has occurred. Signs of infection include, but are not limited to, redness, tenderness, red steaks, swelling, pustulent discharge, and abnormal healing.

A Bit More

As far as scorpionfish and stonefish encounters go, very severe injuries are indeed typical, but deaths are nevertheless very uncommon. And, in some reports, death did not occur until many days or even weeks after the initial injury, leading to the belief that these fatalities were more likely the result of complications arising from infection of the wound. In one well-documented report of death due to stonefish envenomation in the medical literature, it is believed that the venom was injected directly into a larger blood vessel, and thus was able to spread rapidly throughout the victim's body; specially bad luck for the victim. But, in general, chances for survival are good if timely medical treatment is provided, even in the worst cases.

To finish, if you are a diver and you should happen to get stung while underwater, don't get the bends trying to surface too quickly. You'll likely be much better off taking your time surfacing and then dealing with the wound, rather than being placed in a decompression chamber and having to deal with the wound inside the chamber. If you fear that you may be suffering from symptoms of decompression-related sickness, you must make medical personnel aware of this immediately, regardless of the intensity of pain caused by a sting!

Stay out of trouble…

*The first aid and further medical treatment discussed in this article have been taken from various sources that provide information given by medical professionals. It is in no way intended to be a substitute for professional medical care in the event of a scorpaenid fish envenomation, and is given strictly for information purposes.

If you have any questions about this article, please visit my author forum on Reef Central.


Gallagher, S. A. 2001. Lionfish and Stonefish. eMedicine Journal, 2 (7).

Garyfallou, G.T. and Madden J.F. 1996. Lionfish envenomation. Annals of Emergency Medicine, 28 (4): 456-457.

Guenin, D. G. and Auerbach, P. S. 1996. Trauma and envenomations from the marine fauna. In: Emergency Medicine: A Comprehensive Study Guide, 4th edition (Tintinalli, J. E., Ruiz, E., and Krome, R. L. editors). McGraw-Hill, New York. pp. 868-873.

Kizer, K.W., McKinney H.E., and Auerbach P.S. 1985. Scorpaenidae envenomation: a five-year poison center experience. JAMA, 253: 807-810.

Michael, S. W. 2001. Marine Fishes. TFH Publications, Neptune City, NJ. 447 pp.

Otten, E. J. 1998. Venomous animal injuries. In: Emergency Medicine: Concepts and Clinical Practice, 4th edition (Rosen, P., editor). Mosby Year Book, St. Louis. pp. 924-932.

Patel, M.R. and Wells, S. 1993. Lionfish envenomation of the hand. Journal of Hand Surgery, 18 (3): 523-525.

Trestrail, J. H. and al-Mahasneh, Q. M. 1989. Lionfish sting experiences of an inland poison center: a retrospective study of 23 cases. Veterinary and Human Toxicology, 31 (2): 173-175.

Williamson, J.A., Fenner, P.J., and Burnett, J.W. 1996. Venomous and Poisonous Marine Animals: Medical and Biological Handbook. Univ. New South Wales, Sydney. 800 pp.

Useful Links:

Tetanus info:

Vibrio vulnificus info:

Vibrio parahaemolyticus info:

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Lionfish Envenomations and the Aquarist by James Fatherree -