Common name(s)
Spinytail Round Ray., Panamic Stingray.
Identification
A medium-sized round stingray with a sub-circular disc that is wider than long; width 1.1 x length. Snout obtusely angular. Snout tip extended, especially in adult males. Tip pointed; acutely angular. Anterior margins of disc straight to mildly concave, apices broadly rounded. Disc smooth. Described as having thorns on tail only, but the animal shown on this page (and others examined on the internet) have large thorns from nape to caudal fin. Pelvic fins narrowly triangular with slightly convex posterior margins, length sub-equal to width.
Eyes very small; orbit length 0.16-0.2 x snout length. Mouth strongly arched. Nasal curtain short and skirt-shaped. Nostrils oval.
Tail long and slender-based. Lateral skin folds usually absent. Tail length 56-59% of total length. Caudal sting long and slender, origin at mid-tail. Upper caudal lobe much shorter than lower lobe; 18-21% of total length. Posterior margin of caudal fin narrowly pointed.
Colour
Dorsum uniformly tan to dark brown; unmarked. Upper edge of spiracle pale. Thorns on midline may appear paler or yellowish. Tail brown above, pale laterally. Ventrum pale. Caudal sting pale. Caudal fin with a dark median stripe.
Size
Maximum total length at least 42cm. Length at birth unknown.
Habitat
Sub-tropical to warm-temperate seas. Found on sandy or muddy substrates in shallow bays and slopes from 5-100m.
Distribution
Eastern Pacific. Found from Mazatlan in the Sea of Cortez, Mexico, to Punta Negra in Northern Peru.
Conservation Status
NEAR THREATENED
The Spinytail Round Ray (Urotrygon aspidura) is taken as bycatch of large-scale and small-scale shrimp trawl fisheries across its range and is one of the most abundant elasmobranch bycatch species. It is generally discarded although round rays may be used as bait or fishmeal by artisanal fishers. Tropical Eastern Pacific round rays have life history parameters including very early age-at-maturity (2.3 years for the Spinytail Round Ray) that demonstrate high biological productivity and therefore resilience to fishing mortality. The Spinytail Round Ray is subjected to intense and largely unmanaged fishing pressure throughout most of its range, with little refuge. However, its continued abundance despite high overlap with fisheries suggests that the population may not have declined as much as the declines suspected for some other tropical Eastern Pacific round rays. Indeed, trend data available from Colombia showed that the catch-per-unit-effort of this species remained relatively stable between 1995 and 2007. Overall, due to levels of exploitation from its exposure to inadequately managed fisheries throughout its range, balanced with high biological productivity and stable trends in Colombia, it is suspected that the Spinytail Round Ray has undergone a population reduction of 20–29% over the last three generations (15 years), and it is assessed as Near Threatened (close to meeting Vulnerable A2d).
Citation
Kyne, P.M., Charvet, P., Areano, E.M., Cevallos, A., Espinoza, M., González, A., Herman, K., Mejía-Falla, P.A., Morales-Saldaña, J.M., Navia, A.F. & Velez-Zuazo, X. 2020. Urotrygon aspidura. The IUCN Red List of Threatened Species 2020: e.T161689A124528276. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161689A124528276.en. Accessed on 20 January 2022.
References
DESCRIPTIONS OF NINETEEN NEW SPECIES OF FISHES FROM THE BAY OF PANAMA. By DAVID S. JORDAN and CHARLES H. GILBERT.
Bulletin of the United States Fish Commission. 1:306–335. 1882
Reproduction
Aplacental viviparous. Females mature at 2.3yrs. Poorly known.
Diet
Diet unknown. Probably small crustaceans, mollusks, and fishes.
Behavior
Unknown. One animal observed resting in a depression in the sand (probably excavated by a larger ray) at 21m.
Reaction to divers
The only spinytail round ray that I have encountered, bolted immediately.
Diving logistics
According to fishermen, the spinytail round ray is fairly common in Panama Bay but there is no diving infrastructure in that area and the visibility is very poor.
I encountered this species at 20m depth near Playa Ocotal in northern Costa Rica. Sightings are rare but images of this species exist from the same area so this may be a good place to look for them.
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Similar species
Rogers Round Ray Quite similar but distinguishable by a few scattered dark spots on disc.
Dwarf Round Ray Similarly shaped but without thorns on midline.