Pacific Electric Ray

Fascinating facts about the Pacific Electric Ray

• A single Pacific electric ray can unleash up to 45 volts of electricity, enough to stun a diver, and its electric organs, about 15% of its body weight, produce a kilowatt of power in bursts lasting just 4–5 milliseconds.
• These rays grow to 1.4 m (4.6 ft) long, can weigh as much as 41 kg (90 lb), and females reach a disc width of 164 cm (65 in) compared with 92 cm (36 in) for males, making the females noticeably broader than the males.
• They live from the surface down to 200 m (660 ft) in sandy flats, rocky reefs, and kelp forests, but one individual was filmed 17 km (11 mi) offshore, swimming 10 m (33 ft) below the surface in water 3 km (1.9 mi) deep, showing they occasionally venture into the open epipelagic zone.
• A female Pacific electric ray gives birth to 17–20 pups every other year, with newborns measuring 18–23 cm (7.1–9.1 in), and the embryos first rely on yolk before receiving “uterine milk” from the mother.
• Telemetry studies reveal they are nocturnal hunters, entering reefs at night to actively chase prey, while spending daylight buried in sediment, an unusual day-night split that helps them avoid predators and conserve energy.

At a glance

About the Pacific Electric Ray

The Pacific electric ray, Tetronarce californica, glides along the sandy flats, rocky reefs and kelp forests of the northeastern Pacific, from Baja California’s Sebastian Vizcaino Bay to British Columbia’s Dixon Entrance. Its rounded pectoral disc, wider than long, is a dark gray, slate or brown canvas sometimes speckled with darker spots, while a stark white ventral side hints at its benthic lifestyle. Growing up to 1.4 m (4.6 ft) and weighing as much as 41 kg (90 lb), the ray’s thick tail bears two unequal dorsal fins and a large triangular caudal fin that together power swift, night-time pursuits. By day it buries itself in sediment, breathing through smooth-rimmed spiracles, and at night it awakens to hunt bony fishes, ambushing prey from the substrate or actively chasing them under the cover of darkness. A surprising trait lies in its electricity: paired kidney-shaped organs, derived from muscle, can discharge up to 45 volts in rapid bursts, delivering up to a kilowatt of power to stun prey or deter threats, a shock strong enough to incapacitate an unwary diver. Beyond its electrifying defense, the ray’s biology is finely tuned for a nomadic, solitary existence. Its oily liver and low-density tissues render it nearly neutrally buoyant, allowing effortless hovering in the water column, while telemetry shows it ventures into the epipelagic zone, even swimming 10 m below the surface 17 km west of Point Pinos. Reproduction is aplacental viviparous; females nurture litters of 17–20 pups with yolk and histotroph, likely birthing them once every other year. Though rarely seen in the Gulf of California and at the fringes of its range, the species thrives along the California coast, where it remains a common yet enigmatic inhabitant of the Pacific’s temperate waters.

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