Lesser electric ray  (Narcine brasiliensis)

Classified as Data Deficient (DD) on the IUCN Red List (1).

The lesser electric ray has a moderately long, rounded snout, a relatively short tail, and a flattened body, which is fused with the enlarged pectoral fins to form a flat, rounded disc (2) (3) (4) (5) (6). Two equal-sized dorsal fins are located behind the rounded, single-lobed pelvic fins, and the triangular tail (caudal) fin is well developed (2) (3) (6). As in other electric rays, the body lacks scales (3) (5) (6). The upper surface varies from dark brown to reddish orange in colour, sometimes with irregular rings, blotches or bars, while the underside is white to yellowish or greenish, with dusky margins to the fins. Juveniles usually have numerous dark rings, loops or blotches with lighter centres (2) (6).

One of the best known features of electric rays is the ability to produce a strong electric discharge, using a pair of large, kidney-shaped electric organs at the bases of the pectoral fins (3) (4) (5) (6). Indeed, the name of this family comes from the Greek ‘narke’, meaning numbness, and the group are often known as ‘numbfish’ (6). The electric shock is usually used to stun prey or to deter predators (4) (5) (6), and the shock produced by the lesser electric ray has been known to knock down humans, although it usually peaks at just 14 to 37 volts. (6).

The lesser electric ray is found in the southwest Atlantic Ocean, in the waters around Brazil, Uruguay and Argentina. The species has recently been divided into Narcine brasiliensis and the closely related Narcine bancroftii, with previous references to the species in the northwest and north central Atlantic, from North Carolina, USA, to Argentina, referring to N. bancroftii. There is still some confusion over the exact range limits of the two species (1).

The lesser electric ray is a slow-swimming bottom dweller, inhabiting shallow coastal waters at depths of up to 40 metres. It is typically found on soft substrates, often burying beneath the sand or mud (1) (2) (3) (6). This ray has been shown to make seasonal movements in response to water temperature and salinity (7), often moving offshore in winter (8).

Little is known about the biology of the lesser electric ray, as most previous data relate to Narcine bancroftii (1). However, it is likely to share similar features with this species. Polychaete worms are likely to make up most of the diet, as well as other invertebrates and small fish (2) (3) (6). Prey is caught using a unique and unusual method which involves protruding the jaws and sucking food into the mouth from below the substrate. Ingested sediment is then filtered out using further protrusions of the jaws, and is expelled from the gills, mouth and spiracles (respiratory openings behind the eye) (3) (9).

The lesser electric ray gives birth to live young, retaining the eggs inside the body until they hatch (1) (4) (5) (6). As in other related species, females may reach sexual maturity at around 29 centimetres in length, and give birth to between 4 and 15 young (2) (6) (8), which measure around 11 to 12 centimetres at birth (2). The young electric rays are born with the ability to give off electric discharges (6).

The lesser electric ray is taken as bycatch in coastal trawl and beach seine fisheries, although no data is available on the levels of catch (1) (3). The low reproductive rate, localised distribution and sluggish nature of electric rays make these fish particularly susceptible to localised population depletions (1) (8), but the lack of detailed data on the lesser electric ray, and uncertainty over distinguishing it from N. bancroftii, make accurately assessing its status difficult (1). Pollution and habitat disturbance are other potential threats (1), and the species has also been reported to be sold as an aquarium fish in Brazil (6).

There are no known conservation measures currently in place for this species. Monitoring of bycatch has been recommended as a priority, and further research is needed to better define the distribution, population size, life history and taxonomy of this ray (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of sharks and rays see:

• Save Our Seas Foundation:
  http://www.saveourseas.com/
• IUCN Shark Specialist Group:
  http://www.iucnssg.org
• Shark Research Institute:
  http://www.sharks.org
• Shark Trust:
  http://www.sharktrust.org/