116 



Fishery Bulletin 102(1) 



scarce from abundant salmonids. These techniques may 

 be useful in identifying other pinniped prey that lack spe- 

 cies-specific structures and would allow managers to better 

 assess the impact of pinniped predation on threatened or 

 endangered species. 



Acknowledgments 



This study was proposed and initiated in collaboration 

 with Joe Scordino. Scat collection and harbor seal counts 

 were conducted by Lawrence Lehman, Kirt Hughes, Mer- 

 rill Gosho, Sharon Melin, and Robert DeLong. The U.S. 

 Coast Guard Umpqua River Station provided boat storage 

 and a location for keeping a chest freezer during the 1997 

 field season. We would like to thank the Oregon Institute 

 of Marine Biology, Charleston, OR, where the samples col- 

 lected during 1997 were processed. We greatly appreciate 

 the collaboration with Conservation Biology Molecular 

 Genetics Laboratory, which resulted in the identification 

 of our salmon remains based on genetic methods. We would 

 also like to thank Susan Reimer who kindly helped us with 

 difficult identifications, as well as Lawrence Lehman and 

 Jason Griffith for their verification of bone and otolith 

 identifications. We thank Patience Browne, Patrick Gearin, 

 John Jansen, Mark Dhruv, and three anonymous review- 

 ers for providing helpful comments on earlier drafts of this 

 manuscript. 



Literature cited 



Bigg, M. A.. G. Ellis, P. Cottrell, and L. Milette. 



1990. Predation by harbour seals and sea lions on adult 

 salmon in Comox Harbour and Cowichan Bay, British 

 Columbia. Can. Tech. Rep. Fish. Aquat. Sci. 1769, 31 p. 

 Bowen, W. D. 



2000. Reconstruction of pinnipeds diets: accounting for 

 complete digestion of otoliths and cephalopod beaks. Can. 

 J. Fish. Aquat. Sci. 57:898-905. 

 Brown, R. F. 



1980. Abundance, movements and feeding habits of the 

 harbor seal, Phoea vitulina, at Netarts Bay, Oregon. M.S. 

 thesis, 69 p. Oregon State Univ., Corvallis, OR. 

 Brown, R. F., S. D. Riemer, and S. Jefferies. 



1995. Food of pinnipeds collected during the Columbia River 

 Area Commercial Salmon Gillnet Observation Program, 

 1991-1994. ODFW (Oregon Dep. Fish Wildlife), Wildlife 

 Diverstiy Program Tech. Rep. 95-6-01, 16 p. 

 Brown, R. F, and S. Kohlmann. 



1998. Trends in abundance and current status of the 

 Pacific harbor seal {Phoea vitulina richardsi) in Oregon: 

 1977-1998. ODFW, Wildlife Diverstiy Program Tech. 

 Rep. 98-6-01, 16 p. 

 Browne, P., J. L. Laake, and R. L. DeLong. 



2002. Improving pinniped diet analyses through identifica- 

 tion of multiple skeletal structures in fecal samples. Fish. 

 Bull. 100:423-433. 

 Butler. U. L. 



1990. Distinguishing natural from cultural salmonid dep- 

 osits in Pacific Northwest North America. Ph.D. diss., 

 218 p. Univ. of Washington, Seattle, WA. 



Cottrell, P. E., A. W. Trites, and E. H. Miller. 



1996. Assessing the use of hard parts in faeces to identify 

 harbour seal prey: results of captive-feeding trials. Can. 

 J. Zool. 74:875-880. 



da Silva, J., and J. Neilson. 



1985. Limitations of using otoliths recovered in scats to 



estimate prey consumption in seals. Can. J. Fish. Aquat. 



Sci. 42:1439-1442. 

 Dellinger, T, and F. Trillmich. 



1988. Estimating diet composition from scat analysis in 

 otariid seals (Otariidae): is it reliable? Can. J. Zool. 66: 

 1865-1870. 



Eschmeyer. W. N, E. S. Herald, and H. Hammann. 



1983. A field guide to Pacific Coast fishes of North America, 

 336 p. Houghton Mifflin Co., Boston, MA. 

 Harvey, J. T. 



1987. Population dynamics, annual food consumption, move- 

 ments and dive behaviors of harbor seals, Phoca vitulina 

 richardsi, in Oregon. Ph.D. diss., 177 p. Oregon State 

 Univ., Corvallis, OR. 



1989. Assessment of errors associated with harbor seal 

 (Phoca vitulina) faecal sampling. J. Zool., Lond. 219: 

 101-111. 



Hawes, S. 



1983. An evaluation of California sea lion scat samples as 

 indicators of prey importance. M.S. thesis, 50 p. San 

 Francisco State Univ. San Francisco, CA. 

 Jobling, M. 



1987. Marine mammal faeces samples as indicators of prey 

 importance — a source of error in bioenergetics studies. 

 Sarsia 72:255-260. 

 Johnson, O, M. Ruckelshaus, W Grant. F. Waknitz, A. Garrett. 

 G. Bryant, K. Neely, and J. Hard. 



1999. Status review of coastal cutthroat trout from Washing- 

 ton, Oregon, and California. NOAA Tech. Memo. NMFS- 

 NWFSC-37, 292 p. 

 King, J. 



1983. Seals of the world, 240 p. Comstock Publishing 

 Assoc, Cornell Univ. Press, New York, NY. 

 Laake, J. L., P. Browne. R. L. DeLong, and H. R. Huber. 



2002. Pinniped diet composition: a comparison of estimation 

 models. Fish. Bull. 100:434-447. 

 Murie, D., and D. Lavigne. 



1985. A technique for the recovery of otoliths from stomach 

 contents of piscivorous pinnipeds. J. Wildl. Manag. 49: 

 910-912. 



1986. Interpretation of otoliths in stomach content analy- 

 ses of phocid seals: Quantifying fish consumption. Can. J. 

 Zool. 64:1152-1157. 



NMFS (National Marine Fisheries Service). 



1997. Investigation of scientific information on the impacts 

 of California sea lions and Pacific harbor seals on salmo- 

 nids and on the coastal ecosystem of Washington, Oregon, 

 and California. NOAA Tech. Memo. NMFS-NWFSC-28, 

 172 p. 



Olesiuk, P. E, M. A. Bigg, G. M. Ellis. S. J. Crockford, and 

 R. J. Wigen. 



1990. An assessment of the feeding habits of harbour seals 

 (Phoca vitulina i in the Strait of Georgia. British Columbia, 

 based on scat analysis. Can. Tech. Rep. Fish. Aquat. Sci. 

 1730. 135 p. 



Orr, A. J., and J. T. Harvey. 



2001. Quantifying errors associated with using fecal sam- 

 ples to determine the diet of the California sea lion {Zalo- 

 phu* califbrnianus). Can. J. Zool. 79:1080-1087. 



