Thursday, July 27, 2006

Torpedo Ray Injury

Frequent correspondent, Jim Grier calls our attention to an interesting posting on one of the boards about a torpedo ray injury. This was posted on the 'scubadiving' board by "TexasTechdiver" with a follow-up posting. It is an interesting account of a commercial diver who was inspecting a pipeline looking for a small oil leak. He called that he was in trouble, felt something like electricity and shock, then became silent. The video that he was wearing showed a stationary sea floor so the rescue diver immediately went down and retrieved the unconscious diver who had thrown up in his Kirby-Morgan hardhat. He was placed in the chamber and the dive ship unmoored and set sail for the coast, in order to decompress. They stabilized him and he was coherent but didn't know what had happened.

The video was retrieved from the boat and reviewed, and showed, moments before the diver lost consciousness, the approach of a sizeable torpedo ray. The sound indicated four separate electrical discharges from the ray that knocked the diver cold. He was lucky to be in a surface supplied hardhat rig, because on SCUBA he would be dead.

The diver is OK. He's getting an extensive workup looking for possible reasons why the extreme reaction to the electrical shocks. Everyone agrees he's very fortunate to be alive, and that the reaction on the dive crew to the incident was 100%. It's nice when things work out. It is thought that the reasons for the attack was that it was night and the ray was attracted to the diver's helmet light.

In a followup posting, TexasTechdiver relates a conversation with a dive accident consultant in which he talked to the consultant that was called in to investigate the torpedo ray incident, who related the debrief of the diver. The diver reported feeling electrical "tingles", then got hit the first time by the ray. The guy monitoring the diver asked how he was, and the diver said he was ok, but didn't know what had hit him. Then he reported feeling tingles again, and got hit again. He said "electricity" and "fish" then got hit a third time. By then he was out and keeling over. He was hit a fourth time, and that was it. The relief diver got down to him within eight minutes of the first hit, which was fortunate, as the stricken diver's helmet was filling with water.

Also, these rays are apparently far less electrically "active" in the day time, which might explains our being able to play with them and living to tell about it.

The medical exam pretty much ruled out any weird pathology on the part of the diver that would have contributed. He was healthy. He has an irregular heartbeat now, and they'll shock him and try to get him lined back out.

The Pacific electric ray (Torpedo californica) can be distinguished by its two dorsal fins and lack of a venomous spine on the tail and can muster up to 50 volts of electricity - enough to stop the heart of a human. Apparently the creature can send a 'bolt' of electricity toward a perceived threat - causing discomfort or pain, so touching the animal is not necessary for an injury.

The bigger Atlantic torpedo ray, occurring from Nova Scotia to Florida and beyond, is even more powerful. It can measure six feet across and weigh 200 pounds. Beachgoers, however, have nothing to fear from either of these species. They live in deep, cold waters and are mostly active at night. Fishermen occasionally catch the Atlantic torpedo in their trawls. Pulling up the net, their hands tingle. They know a ray is in the net before they even see it.

Jay Sisson, a diver working with Wood's Hole has the following to say about this interesting creature.
"I was shown your 'Torpedo Ray Injury" story by our DSO Terry Rioux (I work as a scientific diver for the Woods Hole Oceanographic). A couple years back I was hit by an Atlantic torpedo, twice. I never saw what hit me and my buddy Glenn witnessed all of it, then told me about it later. I was momentarily paralyzed by each hit but suffered no lasting injury. I believe Glenn estimated it's wingspan about 5 ft.
The location was in 52' of water about 1.5 nm south of Martha's Vineyard, at a research tower we maintain there. Torpedo was on the bottom near one of the piles."

Jay Sisson
Woods Hole Oceanographic Inst.
Woods Hole, MA 02543