FIELD GUIDE TO Sharks, Skates, and Ratfish of Alaska Duane E. Stevenson James W. Orr Gerald R. Hoff John D. McEachran $25 Published by Alaska Sea Grant College Program University of Alaska Fairbanks Alaska Elmer E. Rasmuson Library Cataloging in Publication Data Stevenson, Duane E. Field guide to sharks, skates, and ratfish of Alaska / Duane E. Stevenson … [et al.]. – Fairbanks, Alaska : Alaska Sea Grant College Program, University of Alaska Fairbanks, 2007. p. : ill. ; cm. (Alaska Sea Grant College Program, University of Alaska Fairbanks) Includes bibliographic references and index. 1. Chondrichthyes—Alaska—Handbooks, manuals, etc. 2. Sharks—Alaska—Handbooks, manuals, etc. 3. Skates (Fishes)—Alaska—Handbooks, manuals, etc. 4. Chimaeridae—Alaska—Handbooks, manuals, etc. I. Title. II. Stevenson, Duane E. III. Series: Alaska Sea Grant College Program, University of Alaska Fairbanks. QL638.6.S74 2007 ISBN 1-56612-113-2 Credits This book is published by the Alaska Sea Grant College Program, supported by the U.S. Department of Commerce, NOAA National Sea Grant Office, grant NA06OAR4170013, project A/161-01; and by the University of Alaska Fairbanks with state funds. The University of Alaska is an affirmative action/equal opportunity employer and educational institution. Sea Grant is a unique partnership with public and private sectors combining research, education, and technology transfer for public service. This national network of universities meets changing environmental and economic needs of people in our coastal, ocean, and Great Lakes regions. Book design and layout by Jen Gunderson, project coordination and graphics research by Kurt Byers, and production management and copyediting by Sue Keller, of Alaska Sea Grant. Cover art © Ray Troll. Cover design by Phil Raymond, Archetype Graphics, Fairbanks, Alaska. University of Alaska Fairbanks P.O. Box 755040 Fairbanks, Alaska 99775-5040 Toll free (888) 789-0090 (907) 474-6707 • fax (907) 474-6285 www.alaskaseagrant.org Alaska Contents iv Preface v About the Authors vi About the Cover vii Acknowledgments 1 Introduction 4 Using This Guide 6 General Anatomy of Sharks 7 General Anatomy of Skates 8 General Anatomy of Egg Cases 9 Key to the Sharks, Skates, and Ratfish of Alaska 14 Key to Egg Cases of Alaska Chondrichthyans 18 Ratfish Description 20 Shark Descriptions 38 Skate Descriptions 68 Photos of Alaska Sharks 69 Illustrations of Teeth of Alaska Sharks 70 Photos of Alaska Skates 71 Glossary 74 Selected References 76 Photo Sources 77 Index to Common and Scientific Names Inside back cover Map of North Pacific region iii iv Preface The primary purpose of this guide is to encourage and Most of the specimens, photos, and distribution data used in simplify the identification of chondrichthyans—sharks, the production of this guide were obtained during bottom skates, and ratfish—found in Alaska waters. It is intended trawl surveys conducted by the Resource Assessment and for professional fishery biologists as well as nonprofessional Conservation Engineering (RACE) Division of the National audiences. The guide has an identification key, designed Marine Fisheries Service, Alaska Fisheries Science Center primarily for the identification of specimens in hand. In (NMFS AFSC). These surveys provide a wealth of data for addition, color photographs, maps, and diagrams, as well as scientists and fisheries managers throughout the region, and text features such as diagnoses and similar species synopses, represent an invaluable aid to the effective stewardship of are included to aid users interested in rapid identification of Alaska’s marine resources. specimens that cannot be examined closely. We hope this guide will be useful to a broad audience, This guide also includes a key to the egg cases of including professional fishery biologists and fishery observers, chondrichthyans found in Alaska. Because this life stage commercial and recreational fishers, divers, and all others is poorly known for some species, it may not always be interested in learning more about Alaska’s chondrichthyan possible to identify an egg case to the species level. We fish resources. We also hope that this guide will encourage hope that including this preliminary key will stimulate conservation by providing the basis for better management further investigation into the interspecific differences in this and future research, as well as a tool to promote public important and interesting life-history stage. awareness and understanding of these vulnerable and poorly known fishes. Species are arranged in the guide in the order that they appear in the key to adult fishes, with the ratfish first, followed Duane E. Stevenson by sharks and finally skates. In most cases, this means that the James W. Orr most similar species are grouped together. Gerald R. Hoff John D. McEachran About the Authors Duane Stevenson and James Orr are research fisheries Seattle. His research focuses on the biology and ecology of biologists at the National Marine Fisheries Service (NMFS), noncommercial deepwater fish species in the North Pacific. Alaska Fisheries Science Center’s Resource Assessment He has done extensive work on the ecology and reproduction and Conservation Engineering (RACE) Division in Seattle, of skates in Alaska with an emphasis on conservation of their Washington. Their research interests include the taxonomy marine habitats. and systematics of many groups of fishes. In addition to published research, they have worked extensively within John McEachran is a professor in the Department of Wildlife both the AFSC groundfish program and the North Pacific and Fisheries Sciences at Texas A&M University in College Groundfish Observer Program to provide training and Station, Texas. His research concerns the systematics and produce field guides to several groups of Alaska fishes and biogeography of skates and rays, and species diversity and invertebrates. biogeography of fishes of the central western Atlantic. He has also made several contributions to the series FAO Species Gerald Hoff is also a research fisheries biologist at the Identification Guide for Fishery Purposes. NMFS Alaska Fisheries Science Center’s RACE Division in v vi About the Cover Ray Troll is an artist and naturalist based in Ketchikan, Alaska. underappreciated fish. Troll even has a New Zealand species Troll is widely known for his accurate and often “offbeat” of ratfish named after him: Hydrolagus trolli. Troll’s accolades renderings of sea life. His fish-centric art can be seen on include the Alaska Governor’s Award for Individual Artist, T-shirts, in numerous books, and in nationwide museum and an award from the Academy of Natural Sciences for displays. He is a lifelong “sharkophile” and promoter of achievement in natural history arts. See www.trollart.com. 1. Thresher Shark, Alopias vulpinis, to 6.4 m (20 ft). 2 2. Basking Shark, Cetorhinus maximus, to 10 m (35 ft). 1 6 3. Okhotsk Skate, Bathyraja violacea, to 73 cm (2.5 ft). 7 4. Spiny Dogfish, Squalus acanthias, to 2 m (6.5 ft). 4 5. Sleeper Shark, Somniosus pacificus to 4.4 m (14.5 ft). 6. “Leopard Skate,” Bathyraja sp., to 139 cm (4.5 ft). 3 7. Whiteblotched Skate, Bathyraja maculata, to 147 cm (5 ft). 5 8. Big Skate, Raja binoculata, to 204 cm (7 ft). 8 20 9. Commander Skate, Bathyraja lindbergi, to 102 cm (3.5 ft). 9 10. Butterfly Skate, Bathyraja mariposa, to 76 cm (2.5 ft). 11. Salmon Shark, Lamna ditropis, to 3.1 m (10 ft). 10 12. Mud Skate, Bathyraja taranetzi, to 77 cm (2.5 ft). 12 13. Great White Shark, Carcharodon carcharias, to 6.4 m (21 ft). 11 14. Bluntnose Sixgill Shark, Hexanchus griseus, to 4.8 m (16 ft). 19 14 15. Spotted Ratfish, Hydrolagus colliei, to 100 cm (3 ft). 13 16. Brown Cat Shark, Apristurus brunneus, to 71 cm (2.5 ft). 17. Longnose Skate, Raja rhina, to 142 cm (4.5 ft). 18 17 15 18. Deepsea Skate, Bathyraja abyssicola, to 157 cm (5 ft). 16 19. Bering Skate, Bathyraja interrupta, to 86 cm (3 ft). 20. Blue Shark, Prionace glauca, to 3.8 m or more (12.5 ft). Acknowledgments The work on which this guide is based is derived primarily on groundfish trawl surveys conducted by the Alaska from the unpublished research of J.D. McEachran, and was Fisheries Science Center. Others were provided by Nancy enhanced by the field observations of D.W. Kessler and R. Kohler (NMFS Northeast Fisheries Science Center), the North Baxter. It also draws on the published works of Hart (1973), Pacific Groundfish Observer Program, Alexei Orlov (Russian Eschmeyer et al. (1983), and Mecklenburg et al. (2002). The Federal Research Institute of Fisheries and Oceanography authors have received assistance from numerous scientists [VNIRO]), and others. The photo sources are listed on page 76. in the NMFS AFSC Resource Assessment and Conservation Anatomical diagrams and tooth illustrations were prepared by Engineering (RACE) Division, Resource Ecology and Fisheries Duane Stevenson, with many of the tooth illustrations relying Management (REFM) Division, and North Pacific Groundfish on the observations of Bigelow and Schroeder (1948). Stippled Observer Program (NPGOP); as well as the captains and crew line drawings of the sharks were prepared by Tim Gunther of a number of chartered fishing vessels, particularly the F/V (www.gunthergraphics.biz). Theodore Pietsch (University of Aldebaran, F/V Arcturus, F/V Dominator, F/V Gladiator, F/V Washington), David Ebert (Pacific Shark Research Center), Ken Morning Star, F/V Northwest Explorer, F/V Sea Storm, and F/V Goldman (Alaska Department of Fish and Game), and Bob Vesteraalen; and several North Pacific groundfish observers. Lauth (NMFS, Alaska Fisheries Science Center) reviewed earlier The majority of photographs were taken by NMFS personnel versions of this manuscript. vii Introduction Sharks, skates, and ratfish constitute important components chondrichthyans by the presence of a gill cover overlying of Alaska’s marine ecosystems. Most of these fishes are the gill openings.