DIET AND ECOMORPHOLOGY OF THE SANDPAPER SKATE, BATHYRAJA KINCAIDII (GARMAN,1908) FROM THE EASTERN NORTH PACIFIC A thesis submitted to the faculty of Moss Landing Marine Laboratories and California State University, Monterey Bay in partial fulfillment of the requirements for the degree of Master of Science in Marine Science by Christopher Scott Rinewalt May 2007 Copyright 2007 Christopher Scott Rinewalt ALL RIGHTS RESERVED ABSTRACT DIET AND ECOMORPHOLOGY OF THE SANDPAPER SKATE, BATHYRAJA KINCAIDII (GARMAN,1908) FROM THE EASTERN NORTH PACIFIC by Christopher Scott Rinewalt To determine diet, the stomach contents of sandpaper skates, Bathyraja kincaidii (Garman, 1908), were examined from a limited depth and geographic area off central California and from a wider depth and area range along the eastern North Pacific (ENP). The overall diet was dominated by euphausiids and shrimps, but polychaetes, squids, and gammarid amphipods were important secondary prey. Shrimp-like crustaceans, polychaetes, and teleosts were of similar importance in both data sources, but small benthic crustaceans and crabs were comparatively more important in the diet of skates from the ENP whereas cephalopods were more important in central Californian samples. A three-factor MANOVA demonstrated significant differences in the importance of major prey categories by sex, maturity status, and oceanographic season in the central California data. These three main factors explained more variation in diet than interactions between the factors, and season explained the most variance overall. A detailed analysis of the seasonal variation among the prey categories indicated that environmental abundance changes in the most important prey, euphausiids, were coupled with changes in the importance of other prey. Differences in the diet by sex, maturity status, and geographic zone of capture occurred in the ENP. Geographic zone explained the most variance in the diet, though much less than that explained by the central California data. Information on prey availability for these samples was limited, but it appears that latitudinal variation in euphausiids, again the most important prey, may be correlated with changes in the importance of other prey categories. An ecomorphological study of the oral and dental morphology of B. kincaidii was conducted to determine if the intra-specific differences in diet could be linked with associated differences in morphology. Many of the structures associated with feeding grew allometrically, both positively and negatively, and the growth relationships were often different between the sexes. The results of a three-factor MANCOVA revealed that there were frequent significant differences by all of the factors (sex, maturity status, and geographic zone) and their interactions among all of the measured variables. However, variation between the sexes explained approximately one third of all the variance in the measurements in both data sets. The sex*maturity interaction explained the second most amount of variance, indicating that relational differences in the morphology of male and female skates further changed as they matured. The differences among the factor levels in oral and dental morphology were compared with the differences among the same levels determined from the diet study and it was concluded that intra-specific variation in morphology did not correlate well with intra-specific differences in diet. Based on the lack of a relationship, I suggest that intra-specific differences in the morphology of skates, as with other batoids, are related more to mating. The increased mouth width, amount of palatoquadrate protrusion, shorter pre-oral length, and teeth with higher and longer cusps of mature males allows them to better capture and hold females during courtship but such differences do not satisfactorily account for differential exploitation of any prey category. ACKNOWLEDGEMENTS Funding for this research was provided by NOAA/NMFS to the National Shark Research Consortium and Pacific Shark Research Center, and in part by the National Sea Grant College Program of the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration under NOAA Grant no. NA04OAR4170038, project number R/F-199, through the California Sea Grant College Program and in part by the California State Resources Agency. Partial funding was also provided by the American Museum of Natural History Lerner-Gray Grant for Marine Research, the Dr. Earl H. and Ethel M. Myers Oceanographic and Marine Biology Trust and the Packard Foundation. I also wish to express my gratitude to those that helped collect the specimens used in this project. I appreciate the hard work of Don Pearson, John Fields, E.J. Dick, Alex McCall and Churchill Grimes of the NOAA Fisheries SWFSC, Santa Cruz Lab for their coordinated collection of the specimens used in that portion of the diet study. I would also like to thank Keith Bosley, Erica Fruh, Dan Kamikawa, Aimee Keller, Teresa Turk and Victor Simon of the NOAA Fisheries NWFSC for the collection of the WCGS specimens used in both the diet and morphology chapters. Specimens of Bathyraja kincaidii were collected under San Jose State University IACUC permit #801. Regardless of the propriety of doing so, I also humbly acknowledge the Bathyraja kincaidii that were sacrificed for this study. I hope that the use of these specimens furthered human understanding of the world and that it has planted the seed for greater and more important studies in the future. vii In true Moss Landing Marine Labs spirit, there were countless people who assisted me in the various aspects of this project. I would like to thank all the members of the Pacific Shark Research Center and the Ichthyology Lab, including Daniele Ardizzone, Lewis Barnett, Joe Bizzarro, Aaron Carlisle, Chanté Davis, Colleena Perez, Heather Robinson, Wade Smith and Tonatiuh Trejo, who helped with the glamorous job of processing these skates (along with many other elasmobranchs). I offer additional thanks to Aaron and Chanté for their help with my original thesis project. The countless hours lounging in Elkhorn Slough waiting for a Mustelus to jump in my lap were much more enjoyable with those two. Joe and Wade get the ‘Thanks for being who you are’ award. Both of these guys went out of their way on numerous occasions to help not only myself, but anyone at MLML who asked them to. To top it off, they’re infinitely enjoyable to be around. I thank Matt Levey for his patience in the back-and-forth creation of the area maps he provided and Josh Adams for providing the MATLAB program used to generate the randomized cumulative prey curves. Pete Slattery helped me with gammarid amphipod identification and Mike Graham helped with additional statistical questions. I also thank the many faculty and staff of Moss Landing Marine Labs, who were always there whenever I needed their assistance; one cannot complete one’s education without their assistance. I offer my many thanks to the members of my committee. Without their guidance, this work would probably come in at double the length, yet say little more of importance than it does currently. I would like to thank Greg for believing in me (or not knowing better) and accepting me into the MLML Ichthyology Lab, having done little viii more than exchanging a few emails. I’d like to think it was because I’m that talented, but maybe it had something to do with being a fellow Gaucho. I won’t ask. I’d also like to thank him for his patience while I stumbled through one thesis project and then was handed another (this work). Then on top of that, working away on it for months and dumping a nearly complete draft on him all at once and asking for comments (this was common to all my advisors, so I extend my thanks and apologies for this to the other three). I would like to thank Dave for offering me this project (multiple times) and helping me get out of MLML. Dave and Greg did the lion’s share of the editing work of the EBF article, and thus a major portion of my diet chapter. Without those first few drafts, I might not have been able to have the rest of my committee look at it without having to pay some chiropractic bills. I would also like to thank the both of them for securing the funding that allowed me to complete this project without having to flip burgers, and for additional funding to attend two AES conferences. I wish to thank Lara for her work on both of my thesis projects. Firstly, for being just as excited (possibly even more) than I was about my first project, which I could never have hoped to undertake without her guidance. She secured the funding for all the equipment and put a great deal of effort into making it come to fruition (including setting up the tank!), which made it that much more difficult that I was unable to complete the project. I was glad to be able to use what little I knew about ecomorphology to come up with a question I wanted answered in my final project, and have her agree to help and remain on my committee. I would like to thank Jim for agreeing to be on my committee on such short notice and for his quick turnaround on providing comments. He and Lara encouraged me ix to further tighten up my discussions, and I believe it worked well. Jim also broke me of a few poor grammatical habits and gave me ideas for some more work that needs to be done in the field of diet studies. An equally large helping of thanks goes to my family, both the members I had at the start of my Master’s schooling with and the ones I finished with. I would like to thank my parents for their continued emotional and financial support.