Longtail Stingray: Hypanus longus

Family: Dasyatidae
Common name(s)

Longtail Stingray.

Identification

A large stingray with a kite-shaped disc that is wider than long; disc width approximately 1.2 x length. Snout fairly long and obtusely angular with a slightly protruding tip. Anterior margins of disc straight or weakly concave. Pectoral fin apexes tightly rounded or angular. Pelvic fins quite small, with rounded apices.
Eyes large. Snout length 1.4-1.8 x combined eye and spiracle length.
Mouth with 5 oral papillae. Deep labial furrows around mouth. Mouth weakly arched. Nasal curtain skirt shaped with a strongly fringed margin. Nostrils thin, positioned slightly obliquely.
Juveniles devoid of denticles. Adolescents have a very narrow denticle band from nape to mid disc; adults likely similar. Large adults have very small thorns on shoulders, more thorns on midline near nape, and up to 4 larger spear shaped thorns on base of tail. Tail long, tapering gently to filamentous tip. Tail length (when intact) approximately 2-2.2 x disc width. Dorsal finfold reduced to a ridge. Ventral finfold long; height slightly less than adjacent tail thickness. One tail sting usually present.

Colour

Dorsum grey, reddish-brown, or olive grey, with pale areas below eyes and behind spiracles. Ventrum white, with a wide dusky or brownish disc margin. Sides of tail white. Tail beyond caudal sting dusky or black. Ventral fin fold dark.

Size

Maximum disc width 158cm. Disc width at birth 40cm.

Habitat

Sub-tropical/tropical seas. On sandy substrates, often adjacent to rocky reefs. Inshore, continental shelf, and around offshore islands and seamounts. From shallow water to at least 118m.

Distribution

Tropical eastern Pacific. Found from Magdalena Bay in southern Baja to Ecuador, including Revillagigedo and Galapagos Archipelagos.

Conservation Status

VULNERABLE

The longtail stingray is captured in artisanal gillnets, purse seines, and longlines and in industrial shrimp trawl fisheries, which are intense and unmanaged throughout most of its range, and there is no refuge at depth. There are no population trend estimates but there is evidence of declines in Colombia from a short time-series; there was a decrease in the average catch size and in the relative abundance of the Longtail Stingray in the industrial shrimp trawl fishery between 2001 (150.6 cm TL and 0.27 individuals/hour) and 2007 (129.7 cm TL, and 0.09 ind./hr). Due to its large size, high catchability, and suspected limited biological productivity, it is unable to sustain the high levels of fishing pressure it is subject to. Given the level of overlap with inadequately-managed fishing pressure and its lack of refuge at depth (although it may have some refuge in the Galápagos Islands), it is suspected that the Longtail Stingray has undergone a population reduction of 30–49% over the past three generations (84 years) based on levels of exploitation, and it is assessed as Vulnerable A2d.

Citation

Pollom, R., Avalos, C., Bizzarro, J., Burgos-Vázquez, M.I., Cevallos, A., Espinoza, M., González, A., Herman, K., Mejía-Falla, P.A., Morales-Saldaña, J.M., Navia, A.F., Pérez Jiménez, J.C. & Sosa-Nishizaki, O. 2020. Hypanus longusThe IUCN Red List of Threatened Species 2020: e.T60157A124445324. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T60157A124445324.en. Downloaded on 19 February 2021.

Reproduction

Matrotrophic aplacental viviparity. 1-5 pups per litter. Gestation approximately 10-11 months.

Diet

Diet consists mainly of mantis shrimps and small fishes.

Behavior

Sedentary; spends much of the day resting on the substrate.

Reaction to divers

A fairly approachable species if accustomed to divers e.g. at Socorro.

Diving logistics

Longtail stingrays are quite common in the Sea of Cortez. Cabo Pulmo on Baja’s Eastern Cape has one of the best reef systems in the area and is a good area for this species.

I have also encountered numerous longtail stingrays at the Revillagigedo Archipelago aka Socorro. The stingrays at Socorro are used to divers approaching them and are quite tolerant of camera flashes.

Similar species

Diamond Stingray Distinguished by shorter tail and dorsal finfold.