AGE, GROWTH, AND REPRODUCTION OF THE ALEUTIAN SKATE, BATHYRAJA ALEUTICA, FROM ALASKAN WATERS _________________ A Thesis Presented to the Faculty of Moss Landing Marine Laboratories and the Division of Science and Environmental Policy California State University Monterey Bay _________________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Marine Science _________________ by Diane Lee Haas August 2011 © 2011 Diane Lee Haas ALL RIGHTS RESERVED ABSTRACT Age, Growth, and Reproduction of the Aleutian Skate, Bathyraja aleutica, from Alaskan Waters by Diane Lee Haas Master of Science in Marine Science California State University Monterey Bay, 2011 The Aleutian skate (Bathyraja aleutica) is a large deep-water species that commonly occurs in bycatch of Alaskan trawl and longline fisheries. Although prominent in the skate biomass of the eastern Bering Sea (EBS) and Gulf of Alaska (GOA) ecosystems, minimal biological information exists. To increase our understanding of this potentially vulnerable species, and address the possibility for two separate populations in Alaskan waters, the age, growth, and reproduction of B. aleutica was studied. Vertebrae and caudal thorns were examined for age determination, and multiple growth models were evaluated to determine growth characteristics. Skates from the EBS attained maximum ages of 17 years for females and 16 years for males, and the two-parameter -1 von Bertalanffy growth functions generated estimates of k = 0.13 yr and L∞ = 162.1 cm for females, with similar results for males. Skates from the GOA reached 19 years in females and 18 years in males. Growth parameters of female skates from the GOA were -1 estimated as k = 0.11 yr and L∞ = 160.0 cm, whereas males grew faster, with estimates -1 of k = 0.15 yr and L∞ = 138.2 cm. In evaluating reproduction, maturity stages were determined using external morphology and histological analyses. Size at maturity was similar among sexes and regions, however, age at maturity was ~3.5 years greater for skates from the GOA (13.7 yrs) than the EBS (10.4 yrs). Ovarian fecundity reached 60 ova from skates from the EBS skates, and 36 ova for skates from the GOA skates. Both fecundity and ovum diameter increased weakly with size, but not age. The presence of males with mature spermatocysts and gravid females signified reproductive capability during all months sampled. These data indicate B. aleutica is a moderately slow-growing and late-maturing species. Although skates had relatively similar life history characteristics, skates from the GOA had greater longevity, later age at maturity, and lower potential fecundity than skates from the EBS, and may indicate increased vulnerability to fishing pressures. ACKNOWLEDGEMENTS Funding for this project was provided by the North Pacific Research Board (NPRB) under project #510 and by the National Oceanographic and Atmospheric Administration/ National Marine Fisheries Service (NOAA/NMFS) to the National Shark Research Consortium and Pacific Shark Research Center (PSRC). This study also was supported by funds from the David and Lucille Packard Foundation, San José State University, Earl and Ethel Meyers Oceanographic Trust, American Fisheries Society, American Elasmobranch Society, and Western Groundfish Conference. Animal care approval was obtained from the Institutional Animal Care and Use Committee (IACUC #801) at San José State University. Many people provided advice and assistance with skate collections – this study would not have been possible without collaborative efforts such as these. With the National Marine Fisheries Service-Alaska Fisheries Science Center (NMFS-AFSC), I thank Jerry Berger, Eric Brown, Sarah Gaichas, Christopher Gburski, Jerry Hoff, Dan Kimura, Ned Laman, Bob Lauth, Beth Matta, Jay Orr, Frank Shaw, Jim Stark, and Duane Stevenson for letting us participate on survey cruises throughout the eastern North Pacific. I thank Rob Swanson (NMFS-AFSC) for providing valuable support with sampling efforts in Kodiak, and for taking me out catch my first Pacific halibut. With the Alaska Department of Fish and Game (ADF&G), I thank Mike Byerly, Ken Goldman, Tory O’Connell, Lynne Mattes, and Kally Spalinger for their advice on port sampling and allowing us to participate in ADF&G surveys. I was lucky to have participated on two research cruises in the Gulf of Alaska; I thank the crew and scientists of the F/V v Gladiator and R/V Pandalus for their generosity and assistance while processing tons of fish over many beautiful summer days. In particular, I thank Katherine Pearson- Maslenikov (University of Washington) and Cindy Tribuzio (NMFS-AFSC) for helping process skates and for sharing in my joy of spiny lumpsuckers. I also must thank the many NMFS observers who collecting samples throughout the Bering Sea. I thank James Sulikowski (University of New England) and Cheryl Crowder (Louisiana State University) for assisting with histology samples. Thank you to Josh Bauman and Ashley McPeek who volunteered their time (and a little blood – sorry Josh) to help clean vertebrae. Amber Szoboszlai graciously provided translations of Russian journal articles. Thank you to my colleagues at the Department of Fish and Game for their support, especially Sean Hoobler, Scot Lucas, Dave Osorio and Chuck Valle. An amazing community at Moss Landing Marine Labs has provided much help and encouragement. I thank Kenneth Coale, Donna Kline, Drew Seals, Lynn McMasters, Jeffery Arlt, John Witkowski, Rhett Frantz, Jocelyn Douglas, and Joan Parker and the library staff for years (many, many years) of support. I also thank James Cochran and Bubba for always having a smile and making me feel safe during late nights at the lab. Thank you to members of PSRC, who have been involved in countless ways, including sample collections, dissections, conferences, practice talks, long van rides, sea safety training, the list goes on. Wade Smith, Heather Robinson, Chanté Davis, Lewis Barnett, Shaara Ainsley, Jasmine Maurer, Ashley Neway, Simon Brown, Mariah Boyle, and Joe Bizzarro (who also created my map) were particularly instrumental to this study. vi I learned a lot from Wade, especially while going through skate slime on Kodiak. Shaara and I will always share the stresses and joys of the NPRB report together. I will cherish the memories that have been made with many friends at MLML. I loved sharing in costume parties, open houses, carpools, field trips and more. I would especially like to thank Shaara Ainsley, Mariah Boyle, Lewis Barnett, Cassandra Brooks, Simon Brown, Chanté Davis, Cori Gibble, Kristen Green, Ashley Greenley, Phil Hoos, Daphne Molin, Ashley Neway, Erin Loury, Jasmine Maurer, Ben Perlman, Rosemary Romero, Jayna Schaaf-DaSilva, Jöelle Sweeney, Jon Walsh, Megan Wehrenberg, Megan Winton, and Colleen Young. Kim Quaranta, in particular, will always have a special place in my heart. I am so thankful to my committee members. Gregor Cailliet‘s passion for ichthyology is infectious, and I am proud to be his 115th graduate student. Dave Ebert cultivated my interest in elasmobranchs and systematics. I thank him for sending me to Alaska, and for his multiple roles that resulted in my first publications. Thank you to Jim Harvey for his wealth of statistical knowledge and editorial skills that helped me improve as a scientist. I would not have learned as much as I did without the enthusiasm, knowledge, patience, and kindness of my committee. Finally, I thank my family for their encouragement though my long journey. I thank my mom, dad, Donna, Jim and Mary Haas, and Grandma and Grandpa Hardy for believing in me. I thank my husband and best friend Robert Haas for enduring the many ups and downs of my graduate life; for his love, understanding and generosity; and for taking care of our “kids” and me. Here’s to the next chapter in our lives. vii TABLE OF CONTENTS LIST OF TABLES.........................................................................................................ix LIST OF FIGURES ........................................................................................................x CHAPTER ONE: AGE AND GROWTH.......................................................................1 INTRODUCTION...................................................................................................2 METHODS .............................................................................................................6 RESULTS............................................................................................................. 15 DISCUSSION ....................................................................................................... 19 LITERATURE CITED.......................................................................................... 32 TABLES ............................................................................................................... 44 FIGURES.............................................................................................................. 48 CHAPTER TWO: MATURITY AND REPRODUCTION........................................... 61 INTRODUCTION................................................................................................. 62 METHODS ........................................................................................................... 64 RESULTS............................................................................................................. 68 DISCUSSION ......................................................................................................