81 32 32 Technical Report Series Number 93-1 THE ATLANTIC OYSTER DRILL, UROSALPINX CINEREA (SAY), IN NORTHERN COASTAL GEORGIA Randal L. Walker 31 31 Georgia Marine Science Center University System of Georgia Skidaway Island, Georgia 81 The Atlantic Oyster Drill, Urosalpinx cinerea (Say), in northern coastal Georgia Technical Report 93-1 Randal L. Walker Shellfish Research Laboratory Marine Extension Service University of Georgia P. 0. Box 13687 Savannah, Georgia 314lb-0687 The Technical Report Series of the Georgia Marine Science Center is issued by the Georgia Sea Grant College Program and the Marine Extension Service of the University of Georgia on Skidaway Island (P. 0. Box 13687, Savannah, Georgia 31416). It was established to provide dissemination of technical information and progress reports resulting from marine studies and investigations mainly by staff and faculty of the University System of Georgia . In addition, it is intended for the presentation of techniques and methods, reduced data, and general information of interest to industry, local, regional, and state governments and the public. Information contain~d in these reports is in the public domain. If this pre-publication copy is ~ited, it should be cited as an unpublished manuscript. This work was supported by the NOAA Office of Sea Grant, Department of Commerce under grant number NA84-DD-00072. ACKNOWLEDGEMENTS I wish to thank Drs. P. Heffernan, J. KraeJ.ter and Mr. W. Arnold for reviewing and Mr. G. Davidson for editing the ma.~uscript . Special thanks to Mrs. D. Thompson for typing the manuscript and ~1s. C. Ingram for the graphics herein. This work was supported by the Georgia ~ea Grant Program under grant numbers NABOAA-D-00091 and NA84AA-D-00072. i ABSTRACT A survey of the Sapelo Sound to Wassaw Sound area of coastal Georgia was conducted to determine the distribution and abun.iance of the Atlantic oyster drill, Urosalpinx cinerea (Say). Oyster drills 'vere found to be abundant intertidally and widespread throughout the highe·· saline areas of this northern third of coastal Georgia. Drills occur at a larger size (x = 26.6 mm) in coastal Georgia than that reported for populations in more northern U.S. coastal areas, with the exception of those from the seaside of Virginia. All size classes (x- 15, 25, 35, 37, and 42 mm in shell height) of drills tested were capable of preying upon all sizes (mean sizes of 26 mm to 65 mm in shell length) of oysters, Crassostrea virginica (Gmelin) . Oyster drills pose a serious threat to present oyster harvesting or oyster farming in the coastal waters of Georgia . Keywords: drills, Urosalpinx, abundance, distribution, predation, oysters, Crassostrea, Thais, Eupleura ii LIST OF TABLES Table Page 1. The mean shell height of oyster drills, Urosalpinx cinerea, and mean shell length of oysters, Crassostrea virginica, placed into trays to determine prey size selection by -Jarious size classes of drills. 3 2. The mean number± SE of various sizes of OfSters, Crassostrea virginica, consumed by various sizes of drills, Urosalpinx cinerea. 5 3. The range and mean densities of the Atlantic oyster drill, Urosalpinx cinerea, reported from different geographical areas . 9 4. Comparison of shell heights of Urosalpinx .~ inerea from various geographical locations. 10 Appendix Al. Maps of coastal Georgia showing station lo~ations of the Atlantic oyster drill, Urosalpinx cinerea. 15 A2. The map numbers, location, total number of drills collected, range in drill size, mean shell height, and mean density of oyster drills , Urosalpinx cinerea, for the northern coastal waters of Georgia. 23 A3 . The map numbers, location, total numbers of drills collected, range in drill size, mean shell height, and meau density of oyster drills, Urosalpinx cinerea, for the Christmas Cree 1 ~ area of Georgia. 31 iii LIST OF FIGURES Al. Oyster drill, Urosalpinx cinerea, collection stations for Was saw Sound, Georgia. p . 16 A2. Oyster drill, Urosalpinx cinerea, collection stations for Ossabaw Sound, Georgia. p.l7 A3 . Oyster drill, Urosalpinx cinerea, collection stations for Ossabaw Sound, Georgia, continued. p , l8 A4. Oyster drill, Urosalpinx cinerea, collection stations for St. Catherines Sound, Georgia . p.19 AS. Oyster drill, Urosalpinx cinerea , collection stations for Sapelo Sound, Georgia. p . 20 A6. Oyster drill, Urosalpinx cinerea , collection stations for Christmas Creek, Little Cumberland and Cumberland Islands, Georgia. p.21 iv TABLE OF CONTENTS Acknowledgements i Abstract ii List of Tables iii List of Figures iv Table of Contents v Introduction 1 Methodology 2 Results 4 Discussion 6 References 11 Appendix I 15 Appendix II 23 Appendix III 31 v INTRODUCTION The Atlantic oyster drill, Urosalpinx cinerea (Say), is considered a serious oyster, Crassostrea virginica (Gmelin), predator, especially in northern U.S. coastal waters (Federighi, 1931; Galtsolf et al., 1937; Carriker, 1953; Galtsolf, 1964; Manzi, 1970; Huguenin, 1977), whereas oyster drills in coastal Georgia have not been considered a problem. Early reports indicated drills occur only sparingly in Georgia (Galtsolf et al., 1937; Carriker, 1955) . Although oyster drills were reported collected from Ossabaw, St. Catherines, Sapelo, and St. Simons Sound (Hoese, 1969), no data were provided pertaining to abundance or distribution of drills within those sounds. Drills were reported to be absent intertidally along the Duplin River on Sapelo Island (Bahr, 1974) and were reported not to occur in the creek systems about Sapelo Island, Georgia (Hoese and Jurant, 1969). These early reports tend to indicate that oyster drill5 were absent or rare about Sapelo Island. In Wassaw Sound, the northernmost sound of coastal Georgia, oyster drills were reported abundant and widespr~ad throughout the higher saline areas of the sound (Walker, 1981). It is the purpose of this report to determine the abundance and distribution of oyster drills for the northern (Wassaw, Ossabaw, St. Catherines to Sapelo Sound) coastal waters of G<~orgia and to ascertain if current drill populations represent a threat to the development of oyster farming or harvesting. 1 METHODOLOGY The data reported herein was collected by the author from 1977 to 1989 under several projects. Most of the drill data for Wassaw Sound was reported in Walker (1981), while that for the Harris Neck area was reported in Walker (1988). Drills were collected from the southern end of Wassaw Island (a National Wildlife Refuge) while sampling northern quahog, .Hercenaria mercenaria (L.), populations to determine if there were sufficient clam stocks to warrant commercial fishing (unpublished data). Ossabaw and St. Catherines Islands were sampled for oyster drill population3 to provide distributional data for the area between Wassaw Island and Harris Neck at the northwestern end of Sapelo Sound. Drills were collected by taking six 0 . 1 m~ or six 0.02 m2 samples at different oyster beds. All oyster drill densities are reported as numbers per 2 0.1 m • A grid was placed on the oyster bed and oysters and shells within the grid were broken apart and inspected for the presence of oyster drills. Drills were collected, identified to species, co~nted, and measured to the nearest 0.5 mm with Vernier calipers. Measurements were recorded as shell height (i.e., from shell apex to the end of the >iphonal canal). To determine the potential predation effects that various size classes of drills have upon various size classes of oyst:3rs, the following experiment was set up on July 24, 1985. Three replicate trays of oyster drills (N = 20) of each mean size (15, 25, 35, 37, and 42 mm in shell height) were placed into trays containing 10 oysters of each of the foll•Hing mean shell lengths (i.e , , longest possible measurement): 26 mm, 35 mm, 45 mm, 55 mm, and 65 mm (Table 1). Each tray had a total of 50 oysters (10 of each size class) and 20 2 Table 1. The mean shell height of oyster drills, Urosalpinx cinerea, and mean shell length of oysters, Crassostrea virginica, placed into trays to determine prey size selection by various size classes of drills. Tray Mean No. Drill Mean Size ± SE of Oysters per Size Class in rnrn Size in rnrn ± SE 26 35 45 55 65 1 14.9±0.66 27.1±1.3 35.6±0.8 45 . 0±0 . 8 55 . 0±1. 0 65.3±1.2 2 15.0±0.72 27.5±0.7 35.5±0.9 44. 9±1. 0 54. 9±1.1 65.3±1.9 3 15.0±0.75 25 . 5±1.7 35.5±1.0 44.8±0.9 55.3±1.2 65.0±2.4 4 24.9±0.66 27.8±0.8 35.1±1.4 44.9±0.8 55 . 2±0.9 65.6±1.3 5 25.0±0.61 27.5±0.4 35.3±0.7 44.9±0 . 8 55.0±0 . 9 64.9±0.9 6 25.0±0 . 64 25.1±1.0 35.5±0.9 45.2±0.9 55.1±1.3 65. 0±1. 6 7 34.0±0.59 26.0±1.2 34.2±1.2 44.3±0.8 55.3±0.8 65.7±1.9 8 35.0±0.60 25.8±2.0 35.3±0.9 45. 0±1. 2 55.3±0.9 64. 8±1. 5 9 35.0±0.57 24. 7±1. 9 35. 3±1.4 45. 2±1. 0 54.9±0.8 65.2±1.6 10 36.8±0.45 25.7±0.9 35.6±1.0 44.9±0.8 55.0±0.9 65.3±1.5 11 37.0±0.58 27.5±0.5 35. 6±1. 0 44.5±0.8 55. 0±1. 0 64.9±1.5 12 37.1±0.55 24.3±2.0 35.