The Painful, Disabling Sting of a Lionfish

It is a typical night dive in Anilao, a province of Batangas in the Verde Island passage off the Philippine island of Luzon. In the beam of our lights, the reef swarms with life, from octocorals to active crinoids and fire urchins. Nocturnal fish forage, while others crouch in niches in the coral to avoid predators. Swimming along the shallow reef are several lionfish, with long white venomous spines. A strong current ebbs west, and we kick sideways downslope in search of pygmy seahorses and sygnathid fish. Carefully avoiding the fish, my dive buddy, a local guide named Peri, drops down the sloped surface of a dive site named Basketballs (there's a court on land nearby). Above us, other scientists drop from the narrow outrigger canoes in search of new species of fish, corals and invertebrates.

We are on a joint expedition with the California Academy of Sciences and Philippines Natural History Museum to document the marine life in this region. In addition to helping with the fish and sharks, I am the team's documentarian. Peri stops at 90 feet in search of the sea fans that host the pygmy seahorses, and I drop down below him, shining my light on the bottom. I am careful to settle onto a spot clear of coral or lionfish; I regularly see the latter beneath ledges during the day, but at night they are out on the reef. Their aggression toward divers and researchers has been well documented, and I have already experienced fish swimming aggressively towards me, displaying their spines.

The red lionfish is a venomous coral reef fish in the family Scorpaenidae, order Scorpaeniformes. This species is native to the Indo-Pacific region, but has become a huge invasive problem in the Caribbean and along the Atlantic coast of the U.S., along with a sister species, Pterois miles. It has been speculated that this introduction may have been caused in 1992, when Hurricane Andrew destroyed an aquarium in southern Florida, releasing the fish. In the two decades since, the fish have established themselves as a significant invasive species. A voracious fish with high reproductive success, they have proliferated exponentially. Densities in the Caribbean and along the East Coast are orders of magnitude greater than in their native ranges.

The invasiveness of the red lionfish is a growing problem for reef ecosystems. They overpopulate reef areas and display aggressive tendencies, forcing native species to move to waters where conditions might be less than desirable. One likely ecological impact caused by Pterois could be their impact on prey population by directly affecting food web relationships. Some studies suggest that lionfish could be decreasing Atlantic reef diversity by up to 80 percent. They are voracious feeders, and have out-competed snapper and grouper species already compromised by overfishing. Also, it's likely that the reduction in other apex predators like sharks in the region has relieved natural controls over the fish. The good news is that lionfish have infrequently been found in the stomachs of grouper (see our sidebar), and eradication efforts are underway on reefs in Cancun, the Bahamas and in Florida, including underwater lionfish derbies and even lionfish barbecues. Still, the high fecundity of the species makes control a challenge.

Here in Batangas Bay, the fish are common, but if care is practiced, they are not a significant hazard to our team. I find a pair of Sygnathid fish to film, and my attention narrows to the video camera controls and the dance before me, so I don't notice as Peri drifts downstream to another sea fan. The pipefish wrap themselves around each other and I shift in the sand to get a new angle, when suddenly I feel a sharp stabbing pain in my leg. Flashing my light down, I see a large red lionfish scurrying away, spines outstretched. The pain is immediate and intense, and understanding the effects of the venom, I rapidly close up my camera and search for my buddy.

In humans, Pterois venom can cause systemic effects such as vomiting, fever and sweating. In some cases, it has been lethal. The effect of the venom is negatively inotropic (weakening the force of muscular contractions), and positively inotropic (increasing the heart rate). At 100 feet underwater at night in a three-knot current and carrying 60 pounds of camera equipment, I feel my heart racing. I am healthy and not worried about heart problems, but this is serious.

No spines protrude through my 3mm wetsuit, but my leg is already painful to the touch. I see the light of my buddy, now 20 yards down current, and I circle my light to signal distress, but Peri is absorbed with collecting. I must kick back up slope, complete my safety stops and try not to lose ground in the strong ebb. I signal that I am surfacing and don't wait for a response. As the pain moves down my leg, I'm concerned about losing muscle strength and ankle control. With a large video camera housing, lights and a weighted tripod, the kick upstream is formidable, and I'm sucking air hard. I ascend kicking parallel to the shoreline to surface as close to the canoe as possible. With potential loss of muscular control of my right leg, I don't want to surface downstream of the canoe and be unable to reach the boat.

Kicking towards the surface, the burning increases, and I make my safety stop moving up current where I can see the lights of the boat. I feel the loss of power in my right leg and loss of flexion in my ankle. The exertion and pain have caused me to use more air than normal, and my tank is nearing the reserve. Over increasingly painful minutes, I surface and hand up my gear. It's a long wait for the rest of the team, and an even longer ride back to the field station where I receive treatment from Matt Lewin, a San Francisco emergency doctor volunteering his time for the expedition.

I have problems walking on my affected leg, and have lost some muscular control of the right leg. The venom is a heat labile protein, so the typical treatment is to apply a hot pad soaked in water, but the delay means the venom has spread throughout my leg, from my toes to my hip. Matt settles me in and does what he can, which includes hydration and the heat treatment.

By now, touching the affected area is painful, the heat pad is excruciating, and I have lost sensation in my toes. Matt administers an analgesic, and continues to apply hot pads, which I can barely endure. An hour after the sting, my entire leg is burning and my hip, knee and ankle joints are painful. The discomfort causes me to shift and fidget. The intense pain lasts for another few hours, and ultimately subsides to a dull throb. Matt asks if I want more pain medication, but I want to dive the next day so I decide to try to sleep. Overall, it takes me a week to get over the sensitivity in the region. After one month, a red raised welt remains at the site of the sting where the four spines had entered.

We continued to dive over the next two weeks, and many new species of fish and invertebrates have been discovered, but overfishing is heavily affecting this region of biodiversity. In the absence of other predators (we don't see sharks or other large predatory fish), I wonder if the lionfish will fill that niche here and further affect the balance of the reef. Perhaps I will return and find out, but next time, I will definitely keep my eyes peeled for lionfish.

David McGuire is a scientific diver with the California Academy of Sciences, filmmaker, writer and founder of the nonprofit organization Sea Stewards.