Equatorial Skate, Rostroraja equatorialis
Equitorial Skate, Rostroraja equatorialis. First provided by the commercial fishermen of Bahía Kino, Sonora, November 2014. Total Length: 75 cm (2 feet 6 inches); Disc Length: 50 cm (20 inches); Disc Width: 50 cm (20 inches); Tail: 25 cm (9.8 inches). Photographs courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora. Identification courtesy of Clinton A. J. Duffy, Auckland, New Zealand.
The Equitorial Skate, Rostroraja equatorialis, is a member of the Skate or Rajidae Family, and is known in Mexico as raya ecuatorial. Globally, there are thirty-two species in the genus Raja, of which eight are found in Mexican waters, three in the Atlantic and five in the Pacific Ocean.
The Equatorial Skate has a large flattened rhomboid disc that include the head, body, and pectoral fins. They have a pointed head and pointed “wings”. They have a light-brown back and a white underside and the edges of the disc are pale. Their snout and spines are translucent. Their head features large spiracles behind the eyes and a rigid snout. The front edge of the disc can be straight or convex. The disc length and width are similar, whereas the tail is approximately 57% of the disc length. They have 2 dorsal fins at the rear of their tail and do not have a caudal fin. Their pelvic fins have 2 distinct lobes with the rear lobe being the largest. The disc is covered with small, thin, oval based spines without grooves. They have 1 row of thorns from the nape of the neck along the back of the disc to the tail, another row on each side of the tail, a row inside and before the eyes, and 4 or 5 short rows on the edges of the disc opposite the eyes; these thorns make them truly lethal.
The Equatorial Skate is found over sandy bottoms at depths between 18 m (60 feet) and 183 m (600 feet). They reach a maximum of 1.0 m (3 feet 3 inches) in length. They consume shrimp, polychaete worms, and small benthic fish. They are oviparous and lay large eggs in black or dark green leathery shells, known as Mermaid’s Purses, which have an oblong outline with a hollow tendril at each corner used to attach to marine objects. They are produced in pairs with each case containing up to seven embryos. This species is fairly rare and has a limited distribution. The Equatorial Skate is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Equatorial Skate is a resident of Mexican waters of the Pacific Ocean but has limited distribution being found from Guerrero Negro, Baja California, southward along the central and southern coasts of Baja, in the southern 70% of the Sea of Cortez, and along the coast of the mainland south to Guatemala.
The Equatorial Skate can be confused with the California Skate, Beringraja inornata (one row of tail thorns; no thorns on edges of pectoral fins) and the Rasptail Skate, Rostroraja velezi (large thorns on tail; two ocelli spots on back).
From a conservation perspective the Equatorial Skate is currently considered to be Data Deficient. They are taken primarily as a by-catch of deep water shrimp trawls and by shark fishermen on hook and line. They are rare and not considered an important commercial species but are an excellent food fish and sold predominantly in fish tacos.