Re‐Establishment of the Native Oyster, Ostrea Conchaphila, in Netarts Bay, Oregon, USA
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AN ABSTRACT OF THE THESIS OF Pamela Emily Archer for the degree of Master of Science in Marine Resource Management presented on August 6, 2008. Title: Re‐establishment of the Native Oyster, Ostrea conchaphila, in Netarts Bay, Oregon, USA. Abstract approved: Jessica A. Miller Olympia oysters, Ostrea conchaphila, were once common along the west coast of North America. A popular delicacy, native oyster populations began to decline in the late 1800’s due to over‐harvest, degraded water quality, and habitat loss. Interest in re‐establishing the native oyster in a small Oregon estuary, Netarts Bay, culminated in a partnership among The Nature Conservancy, the National Oceanic and Atmospheric Administration, the Oregon Watershed Enhancement Board, and Oregon State University. This study was designed to assess the re‐ establishment progress of the Olympia oyster restoration in Netarts Bay along with subsequent impacts of the restoration on eelgrass (Zostera marina), an important estuarine species. Two brood years (2005 & 2006) of cultch, consisting of O. conchaphila set on clean Crassostrea gigas shell substrate, were outplanted within an extensive, relatively uniform eelgrass bed. Cultch was placed in two experimental locations to determine the effect of cultch cover on native oyster survival, growth, and eelgrass abundance. The percent cover of cultch varied among treatments: “control” (no cultch), “low” (4% cultch cover), “medium” (11% cultch), and “high” (19% cultch). Research objectives were: (1) determination of O. conchaphila density, growth, and reproduction; and (2) quantification of the response of Z. marina abundance and reproduction to cultch cover. Results from 2007 demonstrated that Olympia oysters were capable of growth, reproduction, and recruitment within their former habitat. Cultch cover within treatments did not change throughout the summer and there was minimal shell export out of the experimental location. Oyster size increased from March‐September, 2007: the mean size of the 2005 brood year increased by 10.5 mm, while the 2006 brood year increased by 16.2 mm. Sperm and larvae were found in individuals from both brood years, indicating that oysters were reproductively active. Declines in eelgrass mean percent leaf cover and shoot density were observed with increasing cultch cover. The mean eelgrass percent leaf cover was 15‐22% lower and shoot density was 27‐36% lower in high treatment (19% cultch) plots than in control plots. There were no discernable patterns in the eelgrass response variables of flowering shoot count, blade length, or blade width. The medium treatment (11% cultch), in which oyster densities were statistically similar to the high treatment (19% cultch), did not have statistically significant impacts on eelgrass percent cover or shoot density. We recommend continued testing of the medium treatment (11% cultch), as well as other cultch densities, such as a 50% cultch treatment. Additional monitoring will be needed to determine what, if any, long‐term impacts occur to the eelgrass bed. We also recommend long‐term monitoring of both oysters and eelgrass beds to detect any additional changes at the re‐establishment site. ©Copyright by Pamela Emily Archer August 6, 2008 All Rights Reserved Re‐establishment of the Native Oyster, Ostrea conchaphila, in Netarts Bay, Oregon, USA. by Pamela Emily Archer A THESIS Submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented August 6, 2008 Commencement June 2009 Master of Science thesis of Pamela Emily Archer presented on August 6, 2008. APPROVED: Major Professor, representing Marine Resource Management Dean of the College of Oceanic and Atmospheric Sciences Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Pamela Emily Archer, Author ACKNOWLEDGEMENTS First, I would like to thank Dr. Jessica Miller and Dick Vander Schaaf for allowing me to partake in the initial restoration of Oregon’s native oyster. Their support and guidance inspired me to expand my knowledge and test my boundaries. I would like to thank Dr. Anthony D’Andrea and the College of Oceanic and Atmospheric Sciences for their in‐kind support of my research. Dr. Ralph Garono provided me with my first graduate research experience, and I am indebted to him for that. I would like to thank Dr. Michael Harte and the Marine Resource Management Program at Oregon State University for their assistance and encouragement. I am very appreciative of Dr. D’Andrea and Dr. Robert Wheatcroft for including me into their lab group. Dr. Hal Batcheldor and Dr. Mark Needham each provided welcome recommendations and advice. The National Oceanic and Atmospheric Administration’s West Coast Native Oyster Working Group is a unique organization of inspired intellectuals who provided me with feedback and encouragement. I was also assisted by the faculty and staff at Coastal Oregon Marine Experimental Station and the Hatfield Marine Science Center. I would like to thank the multiple volunteers who helped complete field work during this project: Robbie & Daniel Wisdom, Stefanie Gera, Abby Nickels, Rebecca Tully, Brent Matteson, Marisa Litz, Summer Peterman, A. Miller Henderson, and many others. The oyster group at Netarts Bay also provided assistance and guidance: Mark Wittwer, John Johnson, Sue Cudd and the Whiskey Creek Shellfish Hatchery, Alan Barton, David Stick, and Dr. Chris Langdon. I would like to thank Rhea Sanders and Brent Matteson for providing reviews of this work, and my sister, Stephanie Ann Archer, who assisted with my library research. Many other friends, family members, and colleagues provided me with encouragement and advice, and I would not have been able to complete this work without their valued, unconditional support. CONTRIBUTION OF AUTHORS Dr. Jessica Miller Dr. Miller assisted in the development of the re‐establishment project and the experimental design. Dr. Miller provided academic and research support, helped with field work and overall project logistics. As my major professor, Dr. Miller provided insight and feedback about the project and the development of my research questions. She provided helpful guidance with data analysis, writing, and revising. Dr. Anthony D’Andrea Dr. D’Andrea assisted with data analysis, writing, and revising, and helped provide an ecological framework to the writing. Mr. Dick Vander Schaaf Mr. Vander Schaaf developed the Olympia oyster re‐establishment plan for Netarts Bay, Oregon. He coordinated the grants, funding, outreach, project logistics, set up the re‐ establishment site, and coordinated the oyster outplantings. Mr. Vander Schaaf also assisted with revisions. Mr. David Stick Mr. Stick assisted with oyster DNA extraction and performed the PCR analyses. He also co‐authored the sections on DNA analyses and provided feedback on oyster growth patterns. TABLE OF CONTENTS Page Chapter 1: General Introduction ...................................................................................................... 1 The decline of Ostrea conchaphila and current re‐establishment efforts .................................. 1 Project background ...................................................................................................................... 3 Ecology of Ostrea conchaphila ..................................................................................................... 4 Oyster nutrition ....................................................................................................................... 4 Life history & reproduction of O. conchaphila......................................................................... 5 Reef structures ......................................................................................................................... 5 Ecology of Zostera marina ........................................................................................................... 7 Distribution .............................................................................................................................. 7 Eelgrass and essential fish habitat ........................................................................................... 8 Restoration methods ................................................................................................................... 9 Chapter 2: Ostrea conchaphila re‐establishment .......................................................................... 10 Introduction ............................................................................................................................... 10 Methods ..................................................................................................................................... 13 Site description ...................................................................................................................... 13 Oyster size & growth.............................................................................................................. 16 Oyster reproduction .............................................................................................................. 17 Oyster density ........................................................................................................................ 18 Site characterization .............................................................................................................