MEPS 241:287-304 (2002)  -  doi:10.3354/meps241287

Long-term direct and indirect effects of the 'Exxon Valdez' oil spill on pigeon guillemots in Prince William Sound, Alaska

Gregory H. Golet1,*, Pamela E. Seiser2, A. David McGuire3, Daniel D. Roby4, Julian B. Fischer1, Katherine J. Kuletz1, David B. Irons1, Thomas A. Dean5, Stephen C. Jewett6, Scott H. Newman7

1US Fish and Wildlife Service, 1011 East Tudor Road, Anchorage, Alaska 99503, USA
2Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska 99775, USA
3USGS, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska, Fairbanks, Alaska 99775, USA
4USGS, Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University, Corvallis, Oregon 97331, USA
5Coastal Resources Associates, 5674 El Camino Real, Suite M, Carlsbad, California 92008, USA
6University of Alaska, School of Fisheries and Ocean Sciences, Fairbanks, Alaska 99775, USA
7Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, California 95616, USA
*Present address: The Nature Conservancy, Sacramento River Project, Chico, California 95928-5614, USA. E-mail:

ABSTRACT: We conducted a study to determine mechanisms constraining population recovery of pigeon guillemots Cepphus columba following the 1989 ŒExxon Valdez¹ oil spill. We asked whether recovery was limited by continuing exposure to residual oil, reduced prey availability, or other causes. Our approach was to compare demographic, physiological, and behavioral parameters between an oiled site pre- and post-spill, and between the oiled site and an unoiled site post-spill. Adult mass, body condition, and nestling survival were significantly lower at the oiled site post-spill compared to pre-spill. After the spill, guillemots increased in number at the unoiled site and chicks fledged at significantly heavier weights than at the oiled site, where populations remained depressed. Elevated hepatic cytochrome P4501A (CYP1A), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) enzyme activities detected in adult guillemots a decade after the spill at the oiled site suggest that continued exposure to residual oil may have limited population recovery, although reduced availability of sand lance, a preferred forage fish, may have also played a role. Previous studies conducted at the oiled site demonstrated that guillemot chick growth and reproductive success were positively related to the percentage of high-lipid forage fishes, such as sand lance, in the chick diet. Aspects of sand lance life history and the pattern of 'Exxon Valdez' oil deposition strongly suggest that sand lance were impacted by the spill, although we lack direct evidence of this, and reductions in this species' abundance may have also resulted from natural causes. Our study suggests that the recovery of a top-level generalist predator may be constrained by both direct effects (continued exposure to residual oil) and indirect effects (reduced availability of a key prey species) following a large-scale perturbation. Furthermore, it demonstrates that recovery following oil spills may take considerably longer for certain species than the few years that have been proposed as typical for marine birds.

KEY WORDS: 'Exxon Valdez' · Oil spills · Marine birds · Cepphus columba · Pigeon guillemot · Prince William Sound · Blood parameters · Reproductive performance

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