Bullseye round stingray  (Urobatis concentricus)

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

Like other stingrays, the bullseye round stingray has a flattened body, with expanded pectoral fins that are fused with the body and head to form a round, flat disc (3). However, round stingrays differ from other stingrays in having a significantly shorter tail, about equal to the length of the disc, as well as a well-developed, rounded caudal fin. There are no dorsal fins (2) (4). As its common name suggests, the disc of the bullseye round stingray is roughly circular in shape, with a rounded snout, and is generally light grey with blackish blotches and spots arranged in concentric rows. Two yellowish or cream bands surround the disc (2) (5). The skin is smooth, without spines (2) (5), but a long, venomous spine is located approximately halfway down the length of the tail, and is used in defence (3) (4) (6).

The taxonomy of the bullseye round stingray is currently under investigation, with some believing it to be a colour morph of the round stingray, Urobatis halleri, rather than a full species (1) (7).

The bullseye round stingray has a rather restricted distribution, occurring only in the Gulf of California, Mexico (1) (2) (5) (7).

The bullseye round stingray typically occurs on rocky bottoms in coastal waters, bays, lagoons and estuaries, and also on sandy bottoms near reefs, at depths of around 5 to 20 metres (1) (2) (7).

Almost nothing is known about the biology and life history of this stingray (1). However, like other stingrays, it is likely to be ovoviviparous, meaning the eggs hatch inside the female and the young are born live (4) (6). Reproduction in this species may be similar to the closely related U. halleri, which mates during the winter, and gives birth to three to six young, after a gestation period of around three months (4). As in many rays and skates, the male bullseye round stingray has much more pointed, curved teeth than the female, an adaptation thought to aid the male in grasping the female’s pectoral fins during copulation (8).

Most stingrays spend a lot of time camouflaged on the sea bed, often partially buried, but can swim rapidly when disturbed or when pursuing prey (3). The diet typically includes bottom-dwelling invertebrates, such as crustaceans, molluscs and worms, and small fish. Prey may be exposed by using the pectoral fins and snout to scoop out holes in the sea bed (3) (4). Although not fatal to humans, the venomous tail spine can cause painful wounds if this stingray is stepped on or disturbed (3) (4) (9).

Round stingrays are generally of little commercial value (9), mainly as a result of their small size (1). However, the bullseye round stingray is occasionally taken as bycatch in other fisheries. When caught, it is not usually retained, but the tail is often cut off before returning the stingray to the sea, probably resulting in high mortality (1). The restricted range of the bullseye round stingray may make it particularly vulnerable to any threats, but the lack of available information on its biology, abundance and taxonomy, and on the levels of bycatch, make assessing its conservation status difficult (1).

There are no conservation measures currently in place for the bullseye round stingray. The IUCN recommend that a management plan is required for the conservation and sustainable management of all shark and ray species in Mexico, and investigations are underway to clarify whether the bullseye round stingray is indeed a full species (1). Further research is urgently needed into the biology, abundance and conservation status of this little-known stingray before it can be better protected.

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/