Featured Elasmobranch – Okhotsk Skate

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Featured Elasmobranch – Okhotsk Skate

Photo Copyright: Alexei Orlov

Okhotsk Skate

Bathyraja violacea (Suvorov, 1935)

Order Rajiformes

Identification:  Disc wider than its length, and tail length; rostral angle about 100°, interorbital space broad, concave, and smooth.  Dorsal surface with prickles present on disc border and mid-dorsal line of body; larger spines present on median caudal line amidst smaller prickles.  Horizontal skin folds extend on either side of the tail, enlarging to their caudal ends.  Fifth gill openings moonlike or C-shaped, much smaller than first four-gill openings. Dorsal surface coloration a lilac-violet hue with darker marbled violet, but fades to a grayish brown after preserved; ventral surface and tail are mostly white, sometimes with dark blotches.

Size: This species attains a maximum size of 107 cm total length; males mature at 54 to 73 cm total length and females at 61 to 76 cm length. Size at birth is uncertain.

Distribution: North Pacific Ocean, Bering Sea, off the Commander and Kuril Islands to Hokkaido (Japan) and Sea of Okhotsk. It has been historically documented in the Alaskan waters of the eastern Bering Sea slope; however it has not been observed in recent surveys.

Habitat: Inhabits sandy, sandy-gravel, and muddy-pebbly substrates of the continental shelf and slope waters.  The majority of the population occurs above 600 meters, but has a depth range of 43 to 1,110 meters. These skates appear to prefer a bottom temperature range of -0.9 to 4.2ºC, with most skate occurring between 3 and 3.5ºC.

Biology: Oviparous, with a possible year round reproductive cycle; egg capsules moderate size, oblong with smooth low ridges, broad lateral keel, horns tapering, and byssal threads attached at base of posterior horns and along mid-keel; eggs case indistinguishable from Bathyraja interrupta. They have been estimated to live for up to nine years, with males maturing at 4 to 6 years and females at 5 to 6 years. These skates feed mostly on crustaceans including snow crabs and amphipods, but have also been shown to consume annelid worms, cephalopods, and small bony fishes.

General Interest: Biomass estimates from trawl surveys suggest that this is the sixth most abundant skate in Russian waters, but very few data are available to determine population trends over time.  It does not appear to be as common in the Eastern Bering Sea as it is in the Western Bering Sea, where it is very common. Fisheries operate throughout its range, and it is caught as bycatch in bottom trawl fisheries and in the Greenland Halibut gillnet fishery. The IUCN has classified the Okhotsk skate as Data Deficient.

Kristin Walovich

Pacific Shark Research Center

Moss Landing Marine Laboratories