Featured Elasmobranch – Whiteblotched Skate

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Featured Elasmobranch – Whiteblotched Skate

March 2010

Whiteblotched Skate

Bathyraja maculata (Ishiyama & Ishihara, 1977)

Family Arhynchobatidae (softnose skates)

Identification: A softnose skate with a short, broad, flexible snout; wide, flat interorbital space; disc that is slightly wider than long, broadly rounded pectoral fin apices, a disc surface evenly covered with numerous, small prickles on the dorsal surface, ventral surface mostly smooth. Nuchal thorns present, but orbital and middorsal thorns absent; median row of tail thorns strongly developed, interdorsal thorns absent.  Coloration is a purplish gray with large scattered white blotches on the dorsal surface, lighter gray ventrally.

Size: A moderately large skate reported to reach a total length of 147 cm. Size at birth is about 15-20 cm.

Distribution: This little known skate species ranges from the Sea of Okhotsk to off Kamchatka and the Kuril Islands to the Commander Islands and Cape Navarin to the eastern Bering Sea and Aleutian Islands. It is also occasionally seen in the Gulf of Alaska, and has recently been confirmed from off Southeast Alaska.

Habitat: Contrary to the soft bottom substrate that many skate species occupy the whiteblotched skate appears to inhabitat rocky and hard bottom substrates. It occurs from 73 to 1,193 m deep, but is most common between 200-600 m.

Biology: The reproductive mode, as with all skates, is oviparous. Females and males both mature between 90-100 cm total length. The egg cases are large, densely covered with longitudinal bands of sliky fibers, with the texture beneather these fibers being rough and striated, with minute prickles. What little is known about their diet indicates that they consume teleost fishes, cepahlopods and crustaceans.

General interest: Occasionally taken as by-catch, these skates may be more vulnerable to long-line fisheries as they tend to prefer rocky or hard bottoms rather than soft bottom substrates commonly associated with most skate species. Detailed studies on the life history, e.g. age, growth, and reproduction, are currently under investigation by researchers at the Pacific Shark Research Center.

By David A. Ebert
Pacific Shark Research Center
Moss Landing Marine Laboratories
8272 Moss Landing Road
Moss Landing, CA 95039
debert@mlml.calstate.edu