Earlier this year I wrote of my encounter with the bullseye electric ray in the Gulf of California at Los Islotes. Recently I had my first opportunity to video one of our local torpedo or Pacific electric rays in the Dive Park. I've been visiting the group of wrecks in the Park frequently since this is where the bat rays were recently feeding. Of course I also visit it to pay homage to the "Pisces," an aluminum glassbottom boat formerly owned by Lynn Stokes. In my (ahem) younger days, we used to party on it until the boat crashed into the breakwater in an early 70's storm. On this dive I saw no bat ray "clouds" and was preparing to move on when I caught something in my peripheral vision at a distance. Although it initially looked like a bat ray, I quickly realized it was a torpedo ray swimming in open water at about 70 feet.
I caught up with this slowly moving relative of the sharks and filmed it as it settled down to the sandy bottom. Of course I kept a safe distance away, remembering what happened when one of the Cousteau divers encountered a torpedo ray off Catalina nearly 20 years ago. I was never a Star Trek fan, but the physical resemblance between a torpedo ray in mid-water and the starship Enterprise is obvious even to me. More importantly, its ability to produce an electric field that can temporarily disable a diver is not unlike the force fields the Enterprise used for defense or discharged against Klingon ships... only it is for real!
This shark relative uses its electric discharges to stun its prey, primarily fish (fortunately that does not include divers). Our species often feeds on anchovies, kelp bass and halibut. It is generally a nocturnal feeder, resting buried in the sandy bottom during the day. However, it will attack unwary fish if they wander close to its daytime resting spot. At night it uses its electric sensors to "image" and detect potential prey based on the electric fields they emit. Imagine what we could do with a sixth sense like this. Working under the cover of darkness, the ray slowly drifts towards its dinner, using its tail to move closer thus strengthening the impact of the electric discharge. If it gets close enough, it will lunge forward and fold the modified pectoral fins around the prey if possible to ensure its incapacitation.
The electric discharges originate in two organs located on either side of the head. These organs derive from muscle tissue. Their cells (known as electrocytes) are no longer able to contract like normal muscle cells. Instead they are specialized to produce electric current through the flow of calcium ions (and they don't even drink milk!). Perhaps this is where the calcium in the bones of their prey ends up, since these are cartilaginous fish like sharks and do not have true bones. The electrocytes cells are stacked on top of each other like the plates in a car battery (which is usually only 12 volts!). Some species generate discharges of 220 volts and 20 amps.
Our species is not capable of seriously hurting a human, but it can be a rude awakening for the unwary diver. The name torpedo derives from ancient Greece where it referred to a fish capable of stunning a man with an electric charge. Apparently the Greeks and Romans used another species to treat headaches and gout. Good thing medicine has advanced slightly since then! Right?
Torpedo rays reach lengths of 4 1/2 feet although this one was less than four feet. The nearly circular pectoral fins are fused to the head and are not used much for movement. The well developed tail fin is used for locomotion. Its gray body is covered with dark spots. Our species is found from British Columbia to central Baja California to depths of 1,500 feet. The young are born live from eggs hatched within the female's body. Their gestation period may be 8-10 months.
Using slow and steady motion, I was able to get within 3-4 feet of this beautiful ray without irritating it. After taping for nearly eight minutes, I decided to check my air gauge since I had gone under with only half a tank. I was quickly approaching my limit, so I reluctantly had to leave and slowly rise to my safety stop before I got all the footage I desired. Better safe than sorry... with respect to the air and the possible zap if I irritated my subject. A former student who does fashion photography told me stories about models who get quite irritable and storm off the shooting floor. The electric ray wouldn't be so pleasant to deal with (or so vain either)!
© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.
Starship Enterprise coming in for a landing; torpedo ray
seeking landing area in sand;
resting on sand with pectoral fins raised to expel water from gills; looks harmless, doesn't it?
This document maintained by
Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia