Featured Elasmobranch – Commander Skate

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Featured Elasmobranch – Commander Skate

Featured Elasmobranch  – Commander Skate

Bathyraja lindbergi (Ishiyama and Ishihara 1977)

Order: Rajiformes
Family: Arhynchobatidae

Photo copyright: David Ebert/ PSRC copyright

 

Identification: Flexible, short, broad snout, large, equal sized dorsal fins separated by short space. Lacking scapular and orbital thorns, nuchal and middorsal thorns present. Uninterrupted row of middorsal spines from before scapular arch to first dorsal. Denticles on dorsal surface few and unevenly distributed; ventral surface smooth. Tail length is greater than precaudal length.  Claspers are long and cylindrical with a round tip, extending to middle of tail.  Coloration on dorsal surface is grayish-brown to black, ventral side whitish brown. Tail is dark grayish brown, areas around pectoral and pelvic margins darker, areas around mouth, nostrils and cloaca whitish. B. lindbergi is similar to Bathyraja matsubarai; the two species require further taxonomic evaluation.

 

Size:  Males mature at approximately 78 cm total length and females mature around 85 cm TL. Little growth is observed after maturation. Maximum observed size is 97 cm TL for both males and females. Size at birth is about 17 cm TL.

 

Distribution:  Found in the North Pacific from the western Bering Sea, the Commander islands, Sea of Okhotsk near Hokkaido, to the eastern Bering Sea, occasionally in the Gulf of Alaska to SE Alaska.

 

 Habitat: Usually found on the outer shelf or upper continental slope at depths of 126-1193m.

 

Biology: Similar to other deepwater skates, the Commander skate likely has species-limiting life history characteristics, such as slow growth and late maturation. Maximum age is estimated at 33 years for females and 31 years for males, and age at maturity is estimated at about 21 to 22 years. The reproductive mode, as in other skates, is oviparity. Egg cases are relatively small (76-79 mm in length), striated, and covered with tiny prickles. Both ovaries are functional and contain oocytes. The diet of B. lindbergi consists primarily of crustaceans, such as shrimps, tanner crabs, and cephalopods. More research is needed regarding horizontal and vertical distributions, and other life history characteristics.

 

 General Interest: The Commander skate is sometimes taken as bycatch by longline fisheries and commercial trawls; however, since their distribution generally falls well below depths operated by these fisheries (<200m), they are likely offered refuge at greater depths. Commander skates are believed to be the second most abundant deepsea skate on the eastern Bering slope, and there is little evidence at this time to suggest this species is being impacted, although there is a lack of species-specific catch data for the species in the western Pacific. The IUCN Red list has classified the Commander skate as being least concern. However, the species and population trend should continue to be monitored, and the status should be reassessed if fisheries operations change.

 

Catarina Pien

Graduate student

Pacific Shark Research Center

Moss Landing Marine Laboratories