18

Spotted Ratfish Hydrolagus colliei

egg case

Diagnosis The only chondrichthyan in Alaska with a single gill opening on each side of the head. Opercle without skeletal support; anterior dorsal fin with a long, sharp spine.

Dentition Teeth fused to form grinding plates.

Coloration Silver to golden brown or green dorsally with many prominent white spots; white ventrally; eyes reflect green.

Body shape Caudal region tapering to a point.

Reproduction Oviparous; accessory clasping organ on head in males. Egg case maximum size is 20 cm long.

Maximum length 100 cm.

Range Gulf of Alaska to Baja California and Gulf of California.

Depth Intertidal to 971 m.

Remarks The spotted ratfish is quite common throughout the Alexander Archipelago and is regularly encountered on NMFS bottom trawl surveys as far north as Lituya Bay. The three isolated records from the northern and western Gulf of Alaska are unverified RACE database records from the mid-1980s.

Similar species The spotted ratfish is the only species of chimaera known from Alaska. One or perhaps two additional undescribed species are known from deep water off California.

In Alaska waters, the spotted ratfish is found in the Gulf of Alaska.

spotted Ratfish Hydrolagus colliei 19

20

Upper tooth

Lower tooth

Spiny DogfishSqualus acanthias

Diagnosis The only Alaska species of shark with a spine on the leading edge of each dorsal fin; anal fin absent.

Dentition Upper and lower teeth with single low cusp.

Coloration Gray to medium brown dorsally, with small white spots; pale gray to white ventrally.

Body shape Elongate, slim, with distinctly heterocercal caudal fin.

Reproduction Viviparous (yolk-sac).

Maximum length 2 m.

Range Worldwide in temperate and subarctic waters.

Depth Generally benthic, intertidal to 1,244 m.

Remarks Although the spiny dogfish has been reported from throughout the Bering Sea and as far north as Kotzebue Sound (Mecklenburg et al. 2002), trawl survey records from the past 15 years indicate that they are very rare in this region.

Similar species The spiny dogfish is the only shark in Alaska with a spine on the leading edge of each dorsal fin. The only other shark in Alaska that lacks an anal fin is the Pacific sleeper shark (see p. 22).

In Alaska waters, the spiny dogfish is found in the Gulf of Alaska and Bering Sea, with one record from Kotzebue Sound.

spiny Dogfish Squalus acanthias 21

22

Pacific Sleeper Shark Somniosus pacificus

Upper tooth

Lower tooth

Diagnosis The only Alaska species of shark with the combination of no anal fin and no dorsal spines.

Dentition Upper teeth long, narrow, and sharp; lower teeth with short low cusps.

Coloration Gray to black dorsally; only slightly lighter ventrally.

Body shape Large, stout, and flabby, with small flaplike, flexible fins.

Reproduction Viviparous (yolk-sac).

Maximum length Documented to 4.4 m, possibly to 7 m or more.

Range North Pacific from Chukchi Sea to Baja California in the eastern Pacific; to Taiwan in the western Pacific.

Depth Benthic, intertidal to 2,000 m.

Remarks The Pacific sleeper shark (sometimes called the mud shark) is encountered throughout the Gulf of Alaska and Aleutian Islands, as well as on the outer shelf and upper slope of the Bering Sea. The Chukchi Sea specimen, reported by Benz et al. (2004), washed up onshore near Point Hope.

Similar species The Pacific sleeper shark is one of only two sharks in Alaska that have no anal fin. The other is the spiny dogfish, which has a strong spine at the leading edge of each dorsal fin. The small, flexible, flaplike fins and posterior position of the first dorsal fin are also characteristic of this species.

In Alaska waters, the Pacific sleeper shark is found in the Bering Sea, Aleutian Islands, and Gulf of Alaska.

Pacific sleeper shark Somniosus pacificus 23

24

Bluntnose Sixgill Shark Hexanchus griseus

Upper tooth

Lower tooth

Diagnosis The only Alaska species of shark with six gill slits on each side of the head; also the only species with a single dorsal fin.

Dentition Lower jaw with 6 comb-shaped teeth.

Coloration Dark gray to brown dorsally; light gray to white ventrally.

Body shape Stout, with broad, rounded head.

Reproduction Viviparous (yolk-sac).

Maximum length 4.8 m.

Range Tropical and temperate North and South Pacific, North and South Atlantic, and Indian Ocean; eastern Aleutian Islands.

Depth Benthic or pelagic, surface to 2,500 m.

Remarks The bluntnose sixgill shark has only been recorded twice in Alaska waters, once south of Unimak Pass (Larkins 1964) and more recently from Southeast Alaska on a 1999 NMFS bottom trawl survey.

Similar species The bluntnose sixgill shark is the only shark in Alaska with six gill slits on each side of the head. The only other sharks in the world with six gill slits are the bigeye sixgill shark (Hexanchus nakamurai), frill shark (Chlamydoselachus anguineus), and sixgill sawshark (Pliotrema warreni), all of which are only found in California waters and farther south.

The bluntnose sixgill shark has been recorded twice in Alaska.

Bluntnose sixgill shark Hexanchus griseus 25

26

Basking Shark Cetorhinus maximus

Upper tooth

Lower tooth

Diagnosis The only Alaska species of shark with gill slits that nearly encircle the head. Also the largest species found in Alaska waters.

Dentition Teeth minute, hooked.

Coloration Brown to gray or black dorsally, often with irregular light patches; lighter ventrally, often with white blotches and spots.

Body shape Large and robust, with elongate snout.

Reproduction Viviparous (oophagous).

Maximum length 10 m or more.

Range Worldwide in temperate seas; northern Gulf of Alaska.

Depth Pelagic, near surface.

Remarks According to Compagno (1984), the range of the basking shark extends to the Kenai Peninsula. The indicated record in the western Gulf of Alaska is from a 1981 NMFS bottom trawl survey.

Similar species The basking shark is the second largest fish in the world (the whale shark is the largest). Its extremely large gill slits and minute hooked teeth distinguish it from all other sharks.

In Alaska waters, the basking shark is found in the Gulf of Alaska.

Basking shark Cetorhinus maximus 27

28

Brown Cat Shark Apristurus brunneus

Upper tooth

Lower toothegg case

Diagnosis The only Alaska species of shark with two dorsal fins and the leading edge of the first dorsal fin posterior to the leading edge of the pelvic fin.

Dentition Teeth with 3-5 cusps, the central cusp largest.

Coloration Uniform dark brown; fin margins darker brown to black.

Body shape Elongate, small; caudal fin long, almost entirely below body midline.

Reproduction Oviparous. Egg case 50 mm.

Maximum size 71 cm.

Range Southeast Alaska to Central or South America.

Depth Benthic, 33-1,306 m.

Remarks The brown cat shark is known from only two Alaska records, both from Southeast Alaska. The northern record was reported by Wilson and Hughes (1978), and the southern record was collected on a 2005 NMFS bottom trawl survey.

Similar Species The brown cat shark is the smallest shark in Alaska. The longnose cat shark (Apristurus kampae) does not occur north of southern Oregon, and can be distinguished from the brown cat shark by its larger gill slits, and white fin edges.

In Alaska waters, the brown cat shark is known from only two records in the Gulf of Alaska.

Brown cat shark Apristurus brunneus 29