66

Whiteblotched Skate Bathyraja maculata

DoRsal

Nuchal

Dorsal diagram showing thorns on disc.

venTRal

egg case

Diagnosis The only Alaska species of Bathyraja with a distinct line on the ventral surface separating the uniformly dark tail from the light body. Also distinguished by the following combination of characters: scapular, orbital, and mid-dorsal thorns absent; nuchal thorns present and strong; ventral surface of disc light to dusky, without denticles.

Denticles Strong, evenly covering dorsal surface; ventral surface smooth.

Coloration Dorsal surface gray with white blotches; ventral surface blotchy gray, with dark border; underside of tail dark, separated from lighter ventral surface of body by distinct line.

Reproduction Oviparous. Egg case small, covered with stringy fibers and rows of slender conical spines ending in one or more tips; keel thin, narrow; byssal threads attached at mid-case and on posterior horns. Egg case

maximum size is 91 mm long by 57 mm wide.

Maximum Size 147 cm.

Range Bering Sea, Aleutian Islands; western Bering Sea to Japan.

Depth 73-1,193 m.

Remarks The whiteblotched skate is common in the Aleutian Islands and on the Bering Sea continental slope. Although it appears to be rare in the Gulf of Alaska, it has recently been recorded as far east as Clarence Strait (J. Bizzarro, Pacific Shark Research Center, Moss Landing Marine Laboratories, pers. comm., 25 July 2006).

Similar Species The whiteblotched skate may be vaguely similar in dorsal coloration to the Aleutian skate, with light blotches on a generally gray background. However, the

whiteblotched skate has only nuchal thorns on the disc, while the Aleutian skate has nuchal, mid-dorsal, and scapular thorns.

In Alaska waters, the whiteblotched skate is found in the Gulf of Alaska, Aleutian Islands, and Bering Sea.

Whiteblotched skate Bathyraja maculata 67

68

Basking Shark

Photos of Alaska Sharks

Spiny Dogfish

Blue SharkThresher Shark

Bluntnose Sixgill Shark

Salmon Shark

Pacific Sleeper Shark

Great White Shark= 1 m

Brown Cat Shark

= 25 cm

69

Brown Cat Shark Thresher Shark Blue Shark Salmon Shark Great White Shark

Illustrations of Teeth of Alaska Sharks

Spiny Dogfish Pacific Sleeper Shark Bluntnose Sixgill Shark Basking Shark

70Photos of Alaska Skates (Dorsal View)

Big Skate

Longnose Skate

Alaska Skate

Aleutian Skate

Whitebrow Skate

Whiteblotched Skate

Roughtail Skate

Roughshoulder Skate

Okhotsk Skate

Mud Skate

“Leopard Skate”

Deepsea Skate

Butterfly Skate

Bering Skate

Commander Skate

= 0.5 m

71

Alar hooks Series of hook-shaped thorns on the dorsal surface near the lateral margins of the disc in male skates.

Benthic At the bottom of a body of water.

Bifid Divided into two equal lobes or parts by a median cleft.

Byssal threads Stringy fibers attached to the lateral edges and horns of egg cases of skates, sharks, and chimaeras.

Case length Smallest distance from the anterior margin of the egg case to the posterior margin, not including the horns.

Case width Greatest distance between the two sides of the egg case, including the keels.

Chondrichthyan A member of the class Chondrichthyes, which includes holocephalans and elasmobranchs.

Clasper A reproductive structure located along the posterior margin of the pelvic fins in male sharks and skates; also on the head in chimaeras.

Cloaca The combined opening of the digestive and urogenital system.

Denticle The hooked, toothlike scales found on sharks and skates.

Dichotomous key A key for the identification of organisms based on a series of choices between alternative characters.

Dimorphic Occurring in two distinct forms.

Disc The body of a skate anterior to the cloaca, composed primarily of the head, visceral cavity, and expanded pectoral fins.

Egg case The leathery protective covering that envelops the developing embryo of chimaeras, skates, and some species of sharks; also known as an egg capsule or mermaid’s purse.

Elasmobranch One of the two major lineages of chondrichthyans, including all living sharks and rays.

Heterocercal A caudal fin in which the upper lobe is larger and more elongate than the lower lobe.

Holocephalan One of the two major lineages of chondrichthyans, represented in the recent fauna only by chimaeras.

Homocercal A caudal fin in which the upper and lower lobe are similar in size and shape.

Horns Elongated extensions of egg cases, usually on all four corners, that taper or curl near the ends.

Glossary

Interdorsal thorns The one or two thorns on the dorsal surface of the tail between the two dorsal fins in skates.

Keel Flattened extensions on the lateral edges of skate egg cases that may extend onto the horns.

Malar hooks Series of hook-shaped thorns on the dorsal surface near the snout in males of some species of skates.

Mid-dorsal thorns A series of thorns on the dorsal surface of a skate along the midline posterior to the scapular thorns and anterior to the pelvis.

Morphological Having to do with general body form and structure.

Nuchal thorns A series of thorns on the dorsal surface of a skate along the midline posterior to the orbits and anterior to the scapular thorns.

Ocellus A round blotch or spot surrounded by a ring of pigment.

Oophagous A form of viviparity in which embryos receive their nutrition from the consumption of additional nonviable ova produced by the female.

Opercle A cartilaginous flap covering the gills and associated structures in chimaeras.

Orbital thorns Thorns along the medial rim of the orbit on the dorsal surface of a skate, highly variable in size.

Ova Eggs.

Oviparous A mode of reproduction in which the female deposits thick leathery egg cases, containing one to several embryos, directly onto the seafloor.

Pelagic Open waters of the sea.

Placental A form of viviparity in which the embryo is nourished directly from the female through a placental tissue.

Precaudal length In skates, the distance from the tip of the snout to the posterior margin of the cloaca.

Pseudosiphon A short groove found near the distal tip of the clasper in some skates.

RACE database (also RACEbase) A resource survey database maintained by the NMFS Alaska Fisheries Science Center’s Resource Assessment and Conservation Engineering (RACE) Division in Seattle, Washington.

Reticulations Lines forming a network.

Serrate Notched or toothed on the edge.

Spine A stiff, sharp fin ray found on the leading edge of the dorsal fins in the spiny dogfish; also see thorn.

Scapular thorns Thorns on the dorsal surface of a skate on either side of the midline posterior to the head.

72Glossary

Tail length In skates, the distance from the posterior margin of the cloaca to the tip of the tail (also known as caudal length).

Tail thorns In skates, a series of thorns on the dorsal midline of the tail posterior to the pelvis and anterior to the dorsal fins.

Thorn An enlarged, conspicuous denticle on the dorsal surface of a skate; also commonly referred to as a spine.

Total length The distance from the anterior-most tip of the snout to the posterior-most tip of the tail.

Total midline thorns The sum of all thorns in the midline series, including nuchal, mid-dorsal, tail, and interdorsal thorns.

Viviparous A mode of reproduction in which the young are born as free-swimming miniature adults after an extended period of development inside the female.

Yolk-sac viviparity A form of viviparity in which the developing embryos are completely dependent on the nutrition provided by a yolk sac inside the female.

73Glossary

74

Bigelow, H.B., and W.C. Schroeder. 1948. Sharks. In: Fishes of the western North Atlantic. Memoirs of the Sears Foundation for Marine Research 1(1):59-546.

Carrier, J.C., J.A. Musick, and M.R. Heithaus (eds.). 2004. Biology of sharks and their relatives. CRC Press, Boca Raton. 596 pp.

Castro, J.I. 1983. The sharks of North American waters. Texas A&M University Press, College Station. 180 pp.

Compagno, L.J.V. 1984. FAO species catalogue. Vol. 4. Sharks of the world: An annotated and illustrated catalogue of shark species known to date. Parts 1 and 2. FAO, Rome. 655 pp.

Compagno, L.J.V. 1999. Checklist of living elasmobranchs. In:W.C. Hamlett (ed.), Sharks, skates, and rays: The biology of elasmobranch fishes. Johns Hopkins University Press, Baltimore, pp. 471-498.

Ebert, D.A. 2003. Sharks, rays, and chimaeras of California. University of California Press, Berkeley. 284 pp.

Eschmeyer, W.N., E.S. Herald, and H. Hammann. 1983. A field guide to Pacific coast fishes of North America from the Gulf of Alaska to Baja California. Houghton Mifflin Co., Boston. 336 pp.

Hamlett, W.C. (ed.). 1999. Sharks, skates, and rays: The biology of elasmobranch fishes. Johns Hopkins University Press, Baltimore, 515 pp.

Hamlett, W.C. (ed.). 2005. Reproductive biology and phylogeny of Chondrichthyes: Sharks, batoids and chimaeras. Science Publishers, Inc., Enfield, New Hampshire. 562 pp.

Hart, J.L. 1973. Pacific fishes of Canada. Fish. Res. Board Can. Bull. 180. 740 pp.

Ishihara, H., and R. Ishiyama. 1985. Two new North Pacific skates (Rajidae) and a revised key to Bathyraja in the area. Jpn. J. Ichthyol. 32:143-179.

Larkins, H.A. 1964. Some epipelagic fishes of the North Pacific Ocean, Bering Sea, and Gulf of Alaska. Trans. Am. Fish. Soc. 93:286-290.

Love, M.S., C.W. Mecklenburg, T.A. Mecklenburg, and L.K. Thorsteinson. 2005. Resource inventory of marine and estuarine fishes of the West Coast and Alaska: A checklist of North Pacific and Arctic Ocean species from Baja California to the Alaska-Yukon border. U.S. Geological Survey, Seattle. 276 pp.

Mecklenburg, C.W., T.A. Mecklenburg, and L.K. Thorsteinson. 2002. Fishes of Alaska. American Fisheries Society, Bethesda. 1037 pp.

Musick, J.A., and R. Bonfil (eds.). 2004. Elasmobranch fisheries management techniques. APEC Fisheries Working Group, Singapore. 370 pp.

Selected References

Sheiko, B.A., and V.V. Fedorov. 2000. Class Cephalaspidomorphi: Lampreys. Class Chondrichthyes: Cartilaginous fishes. Class Holocephali: Chimaeras. Class Osteichthyes: Bony fishes. Chapter 1. In: Catalog of vertebrates of Kamchatka and adjacent waters. Kamchatsky Pechatny Dvor, Petropavlovsk-Kamchatsky, Russia, pp. 7-69.

Stevenson, D.E., and J.W. Orr. 2005. New records of two deepwater skate species from the eastern Bering Sea. Northwestern Naturalist 86(2):71-81.

Stevenson, D.E., J.W. Orr, G.R. Hoff, and J.D. McEachran. 2004. Bathyraja mariposa: A new species of skate (Rajidae: Arhynchobatinae) from the Aleutian Islands. Copeia 2004(2):305-314.

Wilimovsky, N.J. 1954. List of the fishes of Alaska. Stanford Ichthyol. Bull. 4:279-294.

Wilson, D.E., and G.W. Hughes. 1978. The first record of the brown cat shark, Apristurus brunneus (Gilbert, 1891) from Alaskan waters. Syesis 11:283.

Zorzi, G.D., and M.E. Anderson. 1988. Records of the deep-water skates Raja (Amblyraja) badia Garman, 1899, and Bathyraja abyssicola (Gilbert, 1896) in the eastern North Pacific, with a new key to California skates. California Department of Fish and Game 74:87-105.

75Selected References

76

Alopias vulpinus . . . . . . . . . . . . . . . . . .H. Wes Pratt (NMFS Northeast Fisheries Science Center)Amblyraja badia . . . . . . . . . . . . . . . . .G. Hoff (NMFS Alaska Fisheries Science Center)Apristurus brunneus . . . . . . . . . . . . .D. Stevenson (AFSC), UW 29664 (adult)Alopias vulpinus . . . . . . . . . . . . . . . . . .H. Wes Pratt (NMFS Northeast Fisheries Science Center)Amblyraja badia . . . . . . . . . . . . . . . . .G. Hoff (NMFS Alaska Fisheries Science Center)Apristurus brunneus . . . . . . . . . . . . . .D. Stevenson (AFSC), UW 29664 (adult); D. Stevenson (egg case)Bathyraja abyssicola . . . . . . . . . . . .D. Stevenson (adults); G. Hoff (egg case)Bathyraja aleutica . . . . . . . . . . . . . . .G. Hoff Bathyraja interrupta . . . . . . . . . . . .D. Stevenson (dorsal); G. Hoff (ventral, egg case) Bathyraja lindbergi . . . . . . . . . . . . . .G. Hoff Bathyraja maculata . . . . . . . . . . . . .D. Stevenson (dorsal); G. Hoff (ventral, egg case) Bathyraja mariposa . . . . . . . . . . . . .G. Hoff (UW 47197)Bathyraja minispinosa . . . . . . . . . .G. Hoff (dorsal, egg case); D. Stevenson (ventral)Bathyraja parmifera . . . . . . . . . . . . .G. HoffBathyraja sp. cf. parmifera . . . . . . .J. Orr (AFSC)Bathyraja taranetzi . . . . . . . . . . . . .D. Stevenson (dorsal), UW 113189; J. Orr (ventral), UW 113189; G. Hoff (egg case)Bathyraja trachura . . . . . . . . . . . . . .G. HoffBathyraja violacea . . . . . . . . . . . . . .J. Orr (UW 113488, adults); A. Orlov (VNIRO; egg case)Carcharodon carcharias . . . . . . . . . .Greg Skomal (Massachusetts Marine Fisheries)Cetorhinus maximus . . . . . . . . . . . . .marinethemes.com/Saul GonorHexanchus griseus . . . . . . . . . . . . . . .Dan Kamikawa (NOAA Fisheries)Hydrolagus colliei . . . . . . . . . . . . . . .North Pacific Groundfish Observer Program archives (adults); D. Stevenson (egg case)Lamna ditropis . . . . . . . . . . . . . . . . . .Ken Goldman (ADFG)Prionace glauca . . . . . . . . . . . . . . . . .H. Wes Pratt (NEFSC)Raja binoculata . . . . . . . . . . . . . . . . .D. Stevenson (dorsal); K. Maslenikov (ventral; NMFS AFSC); G. Hoff (egg case)Raja rhina . . . . . . . . . . . . . . . . . . . . . . . .K. Maslenikov (adults); G. Hoff (egg case)Somniosus pacificus . . . . . . . . . . . . .S. Kotwicki (AFSC)Squalus acanthias . . . . . . . . . . . . . . .R. Lauth (AFSC)

Photo Sources

77

Alaska skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44Aleutian skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Alopias vulpinus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Amblyraja badia . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Apristurus brunneus . . . . . . . . . . . . . . . . . . . . . . . . . 28Basking shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Bathyraja abyssicola . . . . . . . . . . . . . . . . . . . . . . . . . 58Bathyraja aleutica . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Bathyraja interrupta . . . . . . . . . . . . . . . . . . . . . . . . .48Bathyraja lindbergi . . . . . . . . . . . . . . . . . . . . . . . . . .60Bathyraja maculata . . . . . . . . . . . . . . . . . . . . . . . . .66Bathyraja mariposa . . . . . . . . . . . . . . . . . . . . . . . . . 56Bathyraja minispinosa . . . . . . . . . . . . . . . . . . . . . . .64Bathyraja parmifera . . . . . . . . . . . . . . . . . . . . . . . . .44Bathyraja sp. cf. parmifera . . . . . . . . . . . . . . . . . . .46Bathyraja taranetzi . . . . . . . . . . . . . . . . . . . . . . . . . . 54Bathyraja trachura . . . . . . . . . . . . . . . . . . . . . . . . . . 62Bathyraja violacea . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Bering skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48Big skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Black skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Blue shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Bluntnose sixgill shark . . . . . . . . . . . . . . . . . . . . . . 24Brown cat shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Butterfly skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Carcharodon carcharias . . . . . . . . . . . . . . . . . . . . . 36Cetorhinus maximus . . . . . . . . . . . . . . . . . . . . . . . . . 26Chimaera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Commander skate . . . . . . . . . . . . . . . . . . . . . . . . . .60Deepsea skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Great white shark . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Hexanchus griseus . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Hydrolagus colliei . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Lamna ditropis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34“Leopard skate” . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46Longnose skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Mud shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Mud skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Okhotsk skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Pacific sleeper shark . . . . . . . . . . . . . . . . . . . . . . . . 22Prionace glauca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Raja binoculata . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Raja rhina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Roughshoulder skate . . . . . . . . . . . . . . . . . . . . . . . 38Roughtail skate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Salmon shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Sandpaper skate . . . . . . . . . . . . . . . . . . . . . . . . . . . .48Somniosus pacificus . . . . . . . . . . . . . . . . . . . . . . . . . 22Spiny dogfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Spotted ratfish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Squalus acanthias . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Thresher shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Whiteblotched skate . . . . . . . . . . . . . . . . . . . . . . . .66Whitebrow skate. . . . . . . . . . . . . . . . . . . . . . . . . . . .64

Index to Common and Scientifi c Names

• Biological Field Techniques for Chionoecetes Crabs

• Biological Field Techniques for Lithodid Crabs

• Common Edible Seaweeds in the Gulf of Alaska

• Field Guide to Bird Nests and Eggs of Alaska’s Coastal Tundra

• Guide to Marine Mammals and Turtles of the U.S. Atlantic and Gulf of Mexico

• Guide to Marine Mammals of Alaska

• Guide to Northeast Pacific Flatfishes

• Guide to Northeast Pacific Rockfishes

• Marine Mammals of the Eastern North Pacific (waterproof fold-out brochure)

• North Pacific Albatrosses (laminated identification card)

• Ocean Treasure: Commercial Fishing in Alaska

• The Bering Sea and Aleutian Islands: Region of Wonders

• Many science conference proceedings on marine fisheries biology and management

Field guides and other fine books on Alaska marine resources are available from Alaska Sea Grant:

For full descriptions, prices, and ordering information for alaska sea grant publications and videos, visit our bookstore at

www.alaskaseagrant.org or call toll-free for a free catalog, (888) 789-0090.

Biological Field Techniques for

Lithodid Crabs William E. Donaldson ◆ Susan C. Byersdorfer

Published by Alaska Sea Grant College Program