Gorgona Guitarfish: Pseudobatos prahli

Family: Rhinobatidae

Common name(s)

Gorgona Guitarfish.

Identification

A medium-sized guitarfish with a wedge-shaped snout with a narrowly rounded tip. Rostral ridges relatively broad, adjoined anteriorly then narrowly separated throughout their length. Eyes very large. Snout length ~3 x orbit length. Spiracles have 2 skin folds on posterior margin; outer fold larger than inner. Nostrils large, positioned obliquely. Nasal curtain absent. Large anterior nasal flaps extend well into nostril opening.
Anterior margins of disc weakly undulate. Pectoral apices broadly rounded. Skin completely covered in small denticles. Small thorns around orbits and above spiracles, on shoulders, and along midline and tail.
Tail robust and long; 1.6 x disc length. Dorsal fins tall and well separated, with narrowly rounded or angular apices. Caudal fin triangular, without a defined lower caudal lobe. Caudal fin upper tip acutely tapered.

Colour

Dorsum greyish-brown with diffuse dusky blotches and sparsely scattered, small white spots. Blotches on snout tip and in front of eyes blackish. Anterior region of orbits bright yellow/orange. Rostral cartilage pale. Ventrum pale.

Size

Maximum length 90cm. Size at birth 20-22.5cm.

Habitat

Tropical/sub-tropical seas. Benthic on sand, sometimes adjacent to rocky reefs. From close inshore to 70m.

Distribution

Eastern Pacific. The gorgona guitarfish occurs from southern Mexico to northern Peru.

Conservation Status

VULNERABLE

The Gorgona Guitarfish (Pseudobatos prahli) is a bycatch of large-scale and small-scale shrimp trawl fisheries and small-scale gillnet and longline fisheries. It is rarely encountered in Mexico and is not common in fisheries in Costa Rica, Colombia, and Peru but is abundant in Ecuador where it may be targeted or is taken as bycatch in small-scale fisheries. Fisheries operate throughout most of the range of the species with inadequate management or enforcement, but the species is associated with rocky habitat which would give it some refuge from trawling. Overall, given the intensity of fishing pressure throughout its range (particularly in Ecuador which appears to be its core range) and its susceptibility to capture, it is suspected that the Gorgona Guitarfish has undergone a population reduction of 30–49% over the last three generation lengths (15 years) due to levels of exploitation, and it is assessed as 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. Pseudobatos prahli. The IUCN Red List of Threatened Species 2020: e.T63158A124463727. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T63158A124463727.en. Downloaded on 27 May 2021.

Reproduction

Aplacental viviparous. Litter size 1-6.

Diet

Diet unknown.

Behavior

In Panama, the gorgona guitarfish rests by day in shallow water around offshore islands.

Reaction to divers

Fairly easy to approach. Generally tolerant of divers unless approached too aggressively.

Diving logistics

One of the easiest places to find gorgona guitarfish is around Coiba Island in Panama. A number of dive shops run single or multi day trips to the island from the village of Santa Catalina. The island itself is a protected park with no hotels or restaurants but it is possible to stay in a basic dormitory at the ranger station.
The best time of year to find this and other species of guitarfish at Coiba is during February and March when deepwater upwellings flush the island with very cold water. During other times, lucky divers may still be able to see the occasional guitarfish at deeper dive sites (30m+) below the thermocline.

The gorgona guitarfish is also quite common at dive sites along the Pacific coast of Costa Rica.