Ocellated electric ray  (Diplobatis ommata)

The ocellated electric ray is classified as Vulnerable (VU) on the IUCN Red List (1).

Readily distinguished from other species of ray, the upperside of the ocellated electric ray is marked in the centre with a distinctive bullseye. In common with many rays, the head and upper body of this species form a flattened disc, with large pectoral fins creating a skirt around the edge (2). Two broad pelvic fins are located immediately to the rear of the pectoral fins as the body tapers into a tail, which features two rounded dorsal fins on the upperside and ends in a fan-like caudal fin. The overall colouration is dark brown above with leopard-like spotting and diffuse dark crossbars, and uniform pale below (2) (3). On either side of the head, there are two internal kidney-shaped organs, visible externally as protuberances around the level of the eyes, which are responsible for generating electric shocks (4).

The ocellated electric ray inhabits the eastern-central Pacific, from Baja California, south through the Gulf of California, along the coast of central America as far as Colombia and Ecuador (1).

The ocellated electric ray is common over sandy and rocky bottoms in bays and on coral reefs, from depths of around 2 metres to a maximum recorded depth of 94 metres (1) (5).

Solitary and nocturnal, the ocellated electric ray conceals itself during the day by lying partially buried in the sand, usually near a rocky reef (1). It emerges at night-time to hunt for prey, using its pectoral fins to glide along the bottom while searching for small shrimp, fish and polychaete worms (1) (5). The electricity generating organs at the sides of the head are can deliver a powerful electric shock, which can be employed in defence when threatened (2) (6) (7).

The ocellated electric ray is an ovoviviparous species, which means that it produces eggs that develop and hatch internally, and therefore gives birth to live young. While inside the uterus, the embryos are initially nourished by the egg yolk sac, but once hatched receive additional nourishment from a nutrient-rich fluid produced by the lining of the mother’s uterus. The entire gestation period lasts for around eight to ten months (4).

Owing to the fact that the ocellated electric ray is restricted to shallow water regions, and in many parts of its range occurs in areas where intense trawl fishing takes place, it is taken in large numbers as bycatch. Unfortunately, catch rates for the ocellated electric ray typically go unrecorded, as it is not commercially utilised. The paucity of information means that it is not clear to what extent this accidental mortality is affecting the ocellated electric ray population, but it seems likely that it is having a significant impact (1).

In order to conserve this imperilled species, improved monitoring of bycatch and other fishery impacts is necessary so that appropriate management plans can be implemented. In concert with this measure, more information is required about the ocellated ray’s biology and population to more accurately determine its current conservation status (1).

To learn more about the conservation of sharks and rays visit:

• Save Our Seas Foundation:
  www.saveourseas.com

• IUCN Shark Specialist Group:
  www.iucnssg.org

• Shark Research Institute:
  www.sharks.org

• Shark Trust:
  www.sharktrust.org