Distribution, reproduction and feeding of the Greenland shark Somniosus (Somniosus) microcephalus, with notes on two other sleeper sharks, Somniosus (Somniosus) pacificus and Somniosus (Somniosus) antarcticus

Abstract

Distribution, reproduction and feeding of the Greenland shark Somniosus (Somniosus) microcephalus, with notes on two other sleeper sharks, Somniosus (Somniosus) pacificus and Somniosus (Somniosus) antarcticusThe size and depth distribution, stomach contents and reproductive status of Somniosus (Somniosus) microcephalus, Somniosus (Somniosus) pacificus and Somniosus (Somniosus) antarcticus were examined from specimens collected from the North and South Atlantic, North and South Pacific, and the Southern Ocean. Specimens ranged in size from 42 to 480 cm total length, L T , and were taken from depths of 35-1280 m. Stomach contents included coelenterates, gastropods, cephalopods, echinoderms, crustaceans, elasmobranchs, teleosts, penguins, marine mammals and human waste. Female S. (S.) microcephalus mature at c. 450 cm and S. (S.) antarcticus at c. 435 cm L T ; a female S. (S.) pacificus of 430 cm was mature. Male S. (S.) microcephalus mature at c. 300 cm, but male S. (S.) antarcticus may not mature until c. 400 cm L T . The size at birth in these three species of Somniosus is c. 40 cm L T . # 2007 CSIRO Marine and Atmospheric Research # 2007 CSIRO Marine and Atmospheric ResearchThe three species in the subgenus Somniosus can attain a total length (L T ) of 5-7 m (Compagno, 1984;Cherel & Duhamel, 2004;Compagno et al., 2005). Due to their large size, deep-sea habitat and lack of commercial importance, their biology is poorly known (Castro, 1983;Compagno, 1984;Ebert et al., 1987). This study collected new information on the depth and size distribution, stomach contents and reproductive status of Somniosus (Somniosus) microcephalus, S. (S.) pacificus and S. (S.) antarcticus. MATERIALS AND METHODSA total of 49 S. (S.) microcephalus (64Á8-480Á0 cm L T ) were examined. These included 32 females and 13 males from the western coast of Greenland, one male from Iceland, one male from Boston, U.S.A., and two females from the Canary Islands. Of 34 Somniosus (S.) pacificus (41Á8-430Á0 cm L T ) examined, 14 females and six males were from the eastern Aleutian Islands, Bering Sea and Gulf of Alaska, one male and four females from Japan (Suruga Bay, Sagami Bay and Hiraiso, Ibaraki) and eight females and one male from California, U.S.A. A total of 24 Somniosus (S.) antarcticus (100Á0-438Á0 cm L T ) were examined. These included 14 females and five males from the Tasman Sea and Macquarie Island, three females from South Africa and two males from Namibia.Specimens were caught with demersal trawls, longlines, droplines and gillnets; fishing gear is described in Yano (1995), Yano & Dahlheim (1994) and Yano & Tanaka (1984).Ln-converted L T and mass equations for S. (S.) microcephalus, S. (S.) pacificus and S. (S.) antarcticus were calculated by the least squares method. Curves for these three species (by sex) were fitted to the data using the formula:mass in kg, L T is in cm, and a and b are fitted constants. Stomachs from 39 S. (S.) microcephalus collected from western Greenland waters, 21 S. (S.) pacificus from the Bering Sea, Gulf of ...

In cold blood: evidence of Pacific sleeper shark (Somniosus pacificus) predation on Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska

“…The estimated TL at sexual maturity is 3.7 m for females and 4.0 m for males (on the basis of the length of the few sexually mature individuals ever caught: Ebert et al, 1987;Courtney and Sigler, 2007;Yano et al, 2007). To date, only 5 mature females have been reported from bycatch 2 .…”

“…Pacific sleeper sharks have been documented to reach adult lengths up to 4.4 m TL (Compagno, 1984;Mecklenburg et al, 2002;Yano et al, 2007), but estimates from historic and contemporary photographic and video recordings indicate that they may reach lengths in excess of 7 m TL (Hart, 1973;Compagno, 1984). The estimated TL at sexual maturity is 3.7 m for females and 4.0 m for males (on the basis of the length of the few sexually mature individuals ever caught: Ebert et al, 1987;Courtney and Sigler, 2007;Yano et al, 2007).…”

“…Pacific sleeper sharks have been documented in shallow coastal waters and even in estuarine waters in the arctic regions of the North Pacific and at oceanic depths (>2700 m) in temperate latitudes (Compagno, 1984;Ebert et al, 1987;Sigler et al, 2006;Yano et al, 2007). Although the very large (up to 7 m in total length [TL]) Greenland shark (Somniosus microcephalus) may have the northernmost range documented for species of this genus, the range of the Pacific sleeper shark extends into the Bering Sea and past the Arctic Circle (Bright, 1959;Orlov, 1999;Orlov andMoiseev, 1998, 1999;Benz et al, 2004;Hulbert et al, 2006;Courtney and Sigler, 2007).…”

A tribute to Kazunari Yano (1956–2006)

“…Kazunari was even able to collect data and write papers on those rare and infrequent species that many ichthyologists can only dream about encountering, such as frilled shark Chlamydoselachus anguineus (Tanaka et al, 1990), goblin shark Mitsukurina owstoni (Yano et al, 2007) and megamouth shark Megachasma pelagios (Yano et al, 1997(Yano et al, , 1998(Yano et al, , 1999. Kazunari also described three new species of shark: Japanese velvet dogfish Scymnodon ichiharai (Yano & Tanaka, 1984b), Japanese rough shark Oxynotus japonicus (Yano & Murofushi, 1985) and splendid lantern shark Etmopterus splendidus (Yano, 1988).…”

“…(Yano & Tanaka, 1984b), sleeper sharks Somniosus spp. (Tanaka et al, 1982;Yano et al, 2004Yano et al, , 2007 and viper dogfish Trigonognathus kabeyai (Yano et al, 2003).…”