These rays can produce an electric current strong enough to stun prey and discourage predators. With this formidable defense, electric rays aren't shy—they're bold enough to approach and even chase divers. You can recognize them by their round, flabby bodies, tiny eyes, a gray or bluish-gray back with black spots, and a white underside. They have a short, stocky tail and a large caudal fin.
By night, rays forage two to three feet above sandy bottoms or nearby reefs. They slowly drift over unsuspecting fishes and stun them with an electrical charge. As the electric organ discharges, the ray wraps its disc around the prey to concentrate the electric field and also to manipulate the fish to be eaten whole (head first). During the daytime, rays rest snuggled in sandy or muddy bottoms, but they're awake enough to quickly stun and devour a fish that swims within jolting distance.
Pacific electric rays aren't in danger. Small commercial fisheries catch electric rays for biological and medical researchers, and some are caught by accident in trawls and gill nets. There's no sport fishery for electric rays, perhaps because handling them can be painful!
Electric rays give birth to pups after eggs hatch in the female's uterus. In the later stages of the eight- to 10-month gestation period, the female's uterine lining secretes liquid food for the embryos.
Since contact with a ray's electrical charge can cause numbness, ancient Romans and Greeks called these rays "numbfish." They believed numbfish had therapeutic value and applied the rays to their bodies for treatment of gout, chronic headaches and other maladies. Our English word "narcotic" comes from the Greek work for numbfish, "narke."
Rays can generate and control electrical charges at will. Muscle tissues in two kidney-shaped glands on either side of a ray's head can produce currents of up to 45 volts—an electrical shock strong enough to knock down an adult. These glands weigh one-sixth of the ray's total weight. Even though electric rays can be aggressive, there's no record of them harming humans.