CEPHALOPOD REMAINS FROM STOMACHS OF SPERM WHALES THAT MASS-STRANDED ON THE OREGON COAST A Thesis Presented to the Faculty of Califomia State University, Stanislaus through Moss Landing Marine Laboratories In Partial Fulfillment of the Requirements for the Degree of Master of Science in Mmine Science By Theresa Friend January 2004 DEDICATION To my partner and source of strength and love, without whose constant support and patience this project would not have happened. Thank you for believing in me. iii ACKNOWLEDGMENTS In an undertaking such as this there are so many people to thank. First, I sincerely thank my committee members, Dr. James Harvey, Dr. Pamela Roe, Dr. Gregor Cailliet and Dr. Stacy Kim for their guidance, support, helpfi.1l comments and encouragement. Jim, thank you for the second chance when my first project fell through. I especially thank Dr. Roe for her countless trips to the graduate office to ensure that all of the proper paperwork was in place and for the many phone calls of encouragement when I was sure that this project would not happen. A very special thanks goes to Bill Walker for his immense generosity in helping to identify and verify cephalopod beaks and in training me to identify beaks. It was a tremendous experience. My deepest appreciation goes out to my mom, dad and brother for their constant support and love. Much love and thanks also go out to my extended family (Autumn, Jane, Tam, Kat, and Tom) without whose encouragement and many, many hours of beak measurements, data entry and library searches this project would not have happened. Thank you to Joan Parker and the entire library staff for their assistance in obtaining reference materials. Thank you to Josh Adams and Mike Weise for assistance with questions regarding beak identification and data analysis. iv Many thanks go to Jeff Rutter for his invaluable assistance with the statistics, graphs and pivot tables. Finally, to my partner and best friend, Lisa Scheff, I owe you the world. Your constant support, encouragement, patience and work on this project kept me motivated and on track. You rarely complained about the never-ending piles of squid beaks, papers, books, calipers, microscopes and computer equipment that covered our second bedroom and kitchen table. I can't even begin to thank you for the hours of beak identification and editing you undertook for me. This project was made possible by funding from the David and Lucile Packard Foundation, the Ray Cannon Scholarship, and the Graduate Equity Fellowship from CSU-Stanislaus. v TABLE OF CONTENTS PAGE Dedication ll1 Acknowledgments .................................................................................................... IV List of Tables ........................................................................................................... VII List of Figures ......................................................................................................... IX Abstract ................................................................................................................... x Introduction .............................................................................................................. 1 Current Study ........................................................................................................... 8 Methods.................................................................................................................... 10 Results ...................................................................................................................... 14 Discussion ................................................... ............................................................. 22 Literature Cited ....................................................................................................... 39 Tables ....................................................................................................................... 48 Figures ...................................................................................................................... 61 vi LIST OF TABLES TABLE PAGE 1 Sex, age and number of lower beaks in the stomach contents ......... 49 of 32 sperm whales (ages from Rice et al., 1986) stranded off the Oregon coast. 2 Regression equations used in estimating body lengths and ............. 50 masses of cephalopod prey species in the diet of sperm whales stranded off the Oregon coast. 3 Number and frequency of cephalopodoccurrence of prey recovered 51 from 32 stomachs of 41 sperm whales that stranded off the Oregon coast. 4 Two-dimensional indices of relative importance (IRI) calculated .... 52 by multiplying averaged %N by %FO of cephalopod prey items recovered from 32 stomachs of 41 sperm whales stranded off the Oregon coast. 5 Percentage contribution by mass including minimum, maximum, ... 53 and mean mass of cephalopod prey recovered from 32 stomachs of sperm whales stranded off the Oregon coast. 6 Two-dimensional indices of relative importance (IRI) for each ...... 54 sex and age group of sperm whales, calculated by multiplying averaged %N by %FO of cephalopod prey items recovered from the stomach contents of 32 sperm whales stranded off the Oregon coast. 7 Minimum, maximum and mean dorsal mantle lengths (DML) ....... 56 of cephalopod prey recovered from 32 stomachs of sperm whales stranded off the Oregon coast. 8 Small, medium, med-large and large size classes of cephalopods .... 57 recovered from the stomach contents of 32 sperm whales stranded off the Oregon coast. vii 9 Statistical results for One-Way ANOVA comparison of mean ....... 58 lengths for twelve prey species of cephalopod prey. 10 Cephalopod species recovered from the stomach contents .............. 59 of sperm whales from the Northeastern Pacific Ocean. viii LIST OF FIGURES FIGURE PAGE 1 Location of mass stranding of sperm whales, June 16, 1979, that.. .. 62 stranded off the Oregan coast near the Siuslaw River mouth. 2 Cumulative species curves for 32 spetm whales stranded off the ..... 63 Oregon coast. 3 Total number of beaks for each cephalopod prey item averaged ...... 64 within each whale to detetmine a percentage representation of the prey item for the whole group of whales. 4 Length distributions for 6 cephalopod species recovered from ........ 65 stomach contents of 32 sperm whales stranded off the Oregon coast. 5 Length distributions for 4 cephalopod species recovered from ........ 66 stomach contents of 32 sperm whales stranded off the Oregon coast. 6 Length distributions for Moroteuthis robusta recovered from .......... 67 stomach contents of 32 sperm whales stranded off the Oregon coast. 7 Length distributions for Taningia danae recovered from ................. 68 stomach contents of 32 sperm whales stranded off the Oregon coast. 8 Comparison of the %N represented by the major cephalopod prey .. 69 items consumed by male and female sperm whales. 9 Distribution in the water column of the major cephalopod species .. 70 eaten by the 32 sperm whales that stranded off the Oregon coast. ix ABSTRACT On 16 June 1979, a school of 41 sperm whales stranded on a shallow sloping beach near the mouth of the Siuslaw River in Florence, Oregon. A sample of the stomach contents from 32 of the whales was collected, identified, enumerated, and measured. In the 32 stomachs, 20,247 cephalopod lower beaks were recovered. These beaks represented 24 species from 14 different families. The most numerous species represented were Histioteuthis lwylei (24.4%), Galiteuthis phyllura (13.1 %), Taonius borealis (12.1 %), Moroteuthis robust a (11.1 %), and Gonatopsis/Berryteuthis type (10.9% ). Estimations of contribution by mass to the sperm whales' diets indicated that the dominant species were M. robust a (42.98 % V) followed by Gonatopsis/Benyteuthis type (20.0 1 % V) and H. lwylei (12.26% V). Statistical analysis determined that there was no difference in the overall lengths of the dominant species eaten by male and female sperm whales, however, there was a significant difference in the importance of different species between the diets of male sperm whales (ages 15 to 21), and female sperm whales (ages 11 to 21) and between females of different age groups (ages 11 to 21 and 22 to 58). Based on species composition the sperm whales in this study were feeding in the lower mesopelagic to bathypelagic zones off the Oregon coast. X INTRODUCTION The sperm whale (Physeter macrocephalus Linnaeus, 1758) is an odontocele cetacean (toothed whale) in the family Physeteridae. The family Physeteridae is comprised of two genera: Physeter (sperm whale) and Kogia (pygmy sperm whale; Berzin, 1972). Although there is no doubt that sperm whales are monotypic (Thomas, 1911; Berzin, 1972) there has been some confusion as to the correct species name. Currently, the more widely used name for sperm whales has been P. macrocephalus (Rice, 1998). The body of the sperm whale is streamlined and massive in comparison with other members of the order Cetacea (Berzin, 1972). The species is easily distinguished from other whales by its gigantic and distinctive head. The head is box-like and can constitute from one quarter to one third of the length of the body (Berzin, 1972; Leatherwood & Reeves, 1983; Gordon, 1998). The lower jaw of the sperm whale has up to 30 pairs of conical teeth, whereas the upper jaw has up to 18 pairs of teeth that are rudimentary stumps and no longer functional (Berzin, 1972; Kawakami, 1980; Gordon, 1998). The bottom teeth are firmly attached within sockets in the mandible,