Common name(s)
Diamond Stingray.
Identification
A large stingray with a vaguely kite-shaped disc that is slightly wider than long; disc width approximately 1.1 x length. Snout obtusely angular with a slightly protruding tip. Anterior margins of disc straight or weakly convex. Pectoral fin apices vary from broadly rounded to angular. Pelvic fins large and triangular with rounded apices.
Eyes medium-sized and protruding. Snout length 1.5 x combined eye and spiracle length.
Mouth broad with 5 oral papillae. Deep labial furrows around mouth. Mouth weakly arched. Lower jaw concave at symphysis. Skirt shaped nasal curtain with a weakly fringed margin. Nostrils thin, positioned obliquely.
A row of thorns along midline from nape to caudal tail. Short row of thorns on each shoulder. Tail wide and depressed at base, tapering to end of ventral fold, then filamentous to tip. Tail length (rarely intact) approximately 1.2-1.6 x disc width. Ventral finfold short; length roughly equal to 1/3rd of pre-cloacal disc length. Dorsal finfold short but prominent. Both caudal folds deeper than adjacent tail. One tail sting usually present.
Colour
Dorsum grey, reddish-brown, or olive grey. Ventrum white, usually with a dusky disc margin. Tail beyond caudal sting often dusky or black; darker in juveniles. Ventral fin fold may be pale or very dark.
Size
Maximum disc width 122cm. Disc width at birth 18-23cm.
Habitat
Tropical/sub-tropical seas. On sandy or muddy substrates, often adjacent to reefs, also within kelp beds. From shallow bays to 150m on the continental shelf. Also around offshore islands and seamounts.
Distribution
Tropical eastern Pacific. Found from southern California to central Peru including offshore archipelagos; Revillagigedo to Galapagos. Also recorded from Hawaii.
Conservation Status
VULNERABLE
The diamond stingray is captured in demersal trawl fisheries and in artisanal gillnets and longlines, which are intense and largely unmanaged across its range. It is targeted or retained as bycatch throughout its range, and a demographic analysis indicated that this species has a low intrinsic growth potential and limited capacity to withstand fishing pressure. Landings in artisanal fisheries in the Gulf of California were stable between 1997 and 2009 at ~500 t, but increased after that. It is suspected that this species likely underwent a population reduction prior to this time-series in the 1980s and early 1990s, as gillnet fisheries increased substantially in the area during that time. In Peru, directed gillnet fisheries landings for this species have seen a decline of 50% in annual landed biomass between 1997 and 2015, equivalent to a population reduction of >88% over three generations (57 years). Although data are lacking elsewhere in its range, similar unmanaged fishing pressure exists in other areas and reductions are suspected. It may have some refuge from fishing in southern California and the Hawaiian and Galápagos Islands. Overall, given its life history, the presence of intense and largely unmanaged fishing pressure across most of its range, its lack of refuge at depth, the noted declines and sparsity of records in the southern portion of its range, balanced with its possible refuge from unmanaged fishing in some areas, it is suspected that the Diamond Stingray has undergone a population reduction of 30–49% over the past three generations (57 years) based on levels of exploitation, and it is assessed as Vulnerable A2d.
Citation
Pollom, R., Bizzarro, J., Burgos-Vázquez, M.I., Cevallos, A., Velez-Zuazo, X., Avalos, C., Espinoza, M., González, A., Herman, K., Mejía-Falla, P.A., Navia, A.F., Pérez Jiménez, J.C. & Sosa-Nishizaki, O. 2020. Hypanus dipterurus. The IUCN Red List of Threatened Species 2020: e.T60152A80677563. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T60152A80677563.en. Downloaded on 18 February 2021.
Reproduction
Matrotrophic aplacental viviparity. 1-4 pups per litter. Gestation approximately 3 months.
Diet
Diet consists mainly of worms, crabs, and clams.
Behavior
Sedentary; spends much of the day resting on the substrate.
Reaction to divers
A shy species that is generally difficult to approach but is sometimes tolerant if not approached too closely.
Diving logistics
Diamond stingrays can be encountered throughout their range but they are especially 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 very good area for this species.
I have also encountered diamond stingrays further north in the Midriff Islands, around Loreto, and while snorkeling at numerous remote beaches along the east coast of Baja.
At the other end of their range, diamond stingrays are encountered in the Galapagos Islands.
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Similar species
Longtail Stingray Distinguished by much longer tail and barely visible dorsal finfold.