Spatial distribution and features of biology of Pacific sleeper shark Somniosus pacificus in the North Pacific

Abstract

The results of the investigations of spatial and vertical distribution of Pacific sleeper shark Somnio sus pacificus in the North Pacific Ocean conducted for many years are presented. In addition, the size distri bution and features of biology of the species are studied. The largest abundance of the species is registered in the Bering Sea, western Gulf of Alaska, eastern Aleutian Islands, and Pacific waters of northern Kuril Islands and southeastern Kamchatka. The species is the most abundant near the bottom at the depth from 200 to 700 m and in the pelagic waters at a depth of 100-200 m. The average depths of the catches of Pacific sleeper shark substantially change over the year reaching minimum values in June and maximum values in December. Ver tical daily migrations (to the water column at night and to the bottom during the day) are registered. The catches are represented by fish 26-352 cm in length, and sharks 100-200 cm in length prevail. The males are noticeably smaller than the females. In general, condition of the fishes decreases and feeding intensity increases with growth. Food composition substantially changes with the increase of body length: consump tion of squids decreases and consumption of crustaceans, fishes, and fishery wastes increases. The food com position is slightly different in the females and males.

Pacific sleeper shark Somniosus pacificus trophic ecology in the eastern North Pacific Ocean inferred from nitrogen and carbon stable‐isotope ratios and diet

“…The significant increase in the δ 15 N values of S. pacificus muscle tissue with S. pacificus length found in this study (Table II and Fig. 2) is consistent with previous studies of S. pacificus stomach contents which found evidence of an ontogenetic shift in diet in both the eastern and the western North Pacific Ocean (Orlov, 1999; Orlov & Moiseev, 1999 a , b ; Sigler et al , 2006; Yano et al , 2007). In comparison, similar ontogenetic shifts in prey have also been reported for the Antarctic sleeper shark Somniosus antarcticus Whitley 1939 and for the S. microcephalus (Cherel & Duhamel, 2004; Yano et al , 2007).…”

“…A relatively larger s.e . for δ 15 N consumer of S. pacificus seems reasonable because S. pacificus is a large opportunistic upper trophic level predator with a diet that varies not only ontogenetically and by geographic region, but also by season and capture depth, probably in response to prey availability (Bright, 1959; Gotshall & Jow, 1965; Ebert et al , 1987; Orlov, 1999; Orlov & Moiseev, 1999 a , b ; Yang & Page, 1999; Smith & Baco, 2003; Wang & Yang, 2004; Sigler et al , 2006; Yano et al , 2007).…”

“…61) in May, made up of both squid (teuthoidea) (% N c. 56 ) and giant Pacific Ocean octopus Octopus dofleini (per cent mass; % M c. 25) (Sigler et al , 2006). In comparison, important prey items for S. pacificus in the high latitude western North Pacific include red squid Berryteuthis magister (% N c. 93), giant grenadier Albatrossia pectoralis (Gilbert 1892) (% M c. 18), fish offal (% M c. 16), Kamchatka flounder Atheresthes evermanni Jordan & Starks 1904 (% M c. 15) and O. keta (% M c. 14) (Orlov, 1999; Orlov & Moiseev, 1999 a , b ). In the western North Pacific Ocean, the importance of prey taxa in S. pacificus stomach contents changes with capture depth mostly in relation to the vertical distribution of prey (Orlov & Moiseev, 1999 b ).…”

“…Somniosus pacificus may attain large size [ c. 7 m total length ( L T )], but specimens >430 cm L T have only been reported from estimated lengths (Compagno, 1984; Ebert et al , 1987; Orlov, 1999; Wang & Yang, 2004; Yano et al , 2004, 2007). The diet of S. pacificus varies ontogenetically as well as by season, geographic region and capture depth, probably in response to prey availability (Bright, 1959; Gotshall & Jow, 1965; Ebert et al , 1987; Orlov, 1999; Orlov & Moiseev, 1999 a , b ; Yang & Page, 1999; Smith & Baco, 2003; Wang & Yang, 2004; Taggart et al , 2005; Sigler et al , 2006; Yano et al , 2007). As a result, the trophic ecology of S. pacificus in the eastern North Pacific Ocean is uncertain (Hulbert et al , 2006; Sigler et al , 2006; McMeans et al , 2007).…”

Annotated checklist of the sharks, batoids and chimaeras (Chondrichthyes: Elasmobranchii, Holocephali) from waters of Russia and adjacent areas

“…Remarks: No information is available on type specimens (Eschmeyer, 2014 (Gubanov et al, 1986;Fedorov and Parin, 1998;Amaoka et al, 1989;Sheiko and Fedorov, 2000;Balanov, 2000;Benz et al, 2003;Love et al, 2005;Chereshnev et al, 2005;Rooper and Wilkins, 2008;Shinohara et al, 2009Shinohara et al, , 2014Orlov and Baitalyuk, 2014); Arctic coast of Alaska in the eastern part of Chukchi Sea (Benz et al, 2003;Stevenson et al, 2007;Mecklenburg et al, 2011); probably East Siberian and Beaufort seas Chereshnev and Kirillov, 2007); juvenile specimens from Arctic waters of Greenland (Hussey et al 2014). Marine species.…”