Lee and Sampson: Dietary variations for three rockfish species off the Pacific Northwest 
521 
chronic phenomenon caused by long-term and large- 
scale climate change. 
Although we have attributed the diet variability 
observed in this study to oceanographic changes, with 
supporting evidence from other studies, it should be 
noted that, because of the limited sampling coverage, we 
could not address the question of how much variability 
would be due to inherent interannual variability in the 
diets of these species. Also the prey partitioning and 
diet variability of these species could be a phenomenon 
localized only in the study area. Further monitoring of 
these rockfish species, as well as other fish species in 
the region, coupled with parallel investigations of the 
macrozooplankton community would provide a better 
understanding the relationship between the different 
trophic levels and the potential consequences of diet 
changes to the physiology and population biology of 
these fish species. 
Acknowledgments 
We are grateful to the many people that were involved 
in this project. The sampling aboard FV Pacific would 
not have been possible without consent of its owner, Mr. 
J. Seavers, and help from Captain R. Johnson and his 
crew. We also appreciate the scientists and fishing crews 
who participated in the NMFS 1998 westcoast triennial 
groundfish survey. P. Livingston, M.-S. Yang (Alaska 
Fisheries Science Center, NMFS) provided laboratory 
training in stomach-content identification. R. Brodeur 
provided unpublished data for individual stomachs 
from his previous work. R. Brodeur, P. Livingston, M-S. 
Yang, A. Moles, and four anonymous reviewers provided 
insightful and constructive reviews of the draft manu- 
script. The project was partially funded by a Mamie 
Markham Award from Oregon State University and was 
prepared under award NA77FE0490 from the National 
Oceanic and Atmospheric Administration, U.S. Depart- 
ment of Commerce. 
Literature cited 
Adams, P. B. 
1987. The diet of widow rockfish Sebastes entomelas 
in northern California. NOAA Tech. Rep. NMFS 
48:37-41. 
Arai, M. N., D. W. Welch, A. L. Dunsmuir, M. C. Jacobs, and 
A. R. Ladouceur. 
2003. Digestion of pelagic Ctenophora and Cnidaria by 
fish. Can. J. Fish. Aquat. Sci. 60:825-829. 
Bailey, K. M., R. C. Francis, and P. R. Stevens. 
1982. The life history and fishery of Pacific whiting, 
Merluccius productus. Calif. Coop. Ocean. Fish. Invest. 
Rep. 23:81-98. 
Brodeur, R. D. 
1986. Northward displacement of the euphausiid Nyctipli- 
anes simplex Hansen to Oregon and Washington waters 
following the El Nino event of 1982-83. J. Crustac. 
Biol. 6:686-692. 
Brodeur, R. D., and W. G. Pearcy. 
1984. Food habits and dietary overlap of some shelf rock- 
fishes (genus Sebastes) from the northeastern Pacific 
Ocean. Fish. Bull. 82:269-293. 
Cortes, E. 
1997. A critical review of methods of studying fish feed- 
ing based on analysis of stomach contents: application 
to elasmobranch fishes. Can. J. Fish. Aquat. Sci. 
54:726-738. 
Dill, L. M. 
1983. Adaptive flexibility in the foraging behavior of 
fishes. Can. J. Fish. Aquat. Sci. 40:398-408. 
Gerking, S. D. 
1994. Feeding ecology of fish. Academic Press, San 
Diego, CA. 
Huyer A., R. L. Smith, and J. Fleischbein. 
2002. The coastal ocean off Oregon and Northern Cali- 
fornia during the 1997-98 El Nino. Prog. Oceanogr. 
54:311-341. 
Hyslop, E. J. 
1980. Stomach contents analysis: a review of methods 
and their application. J. Fish Biol. 17:412-429. 
Keister, J. E., T. B. Johnson, C. A. Morgan, and W. T. Peterson. 
2005. Biological indicators of the timing and direction 
of warm-water advection during the 1997/1998 El Nino 
off the central Oregon coast, USA. Mar. Ecol. Prog. 
Ser. 295:43-48. 
Keister, J. E., and W. T. Peterson. 
2003. Zonal and seasonal variations in zooplankton 
community structure off the central Oregon coast, 
1998-2000. Prog. Oceanogr. 57:341-361. 
Lavaniegos, B. E., and M. D. Ohman. 
2003. Long-term changes in pelagic tunicates of the 
California Current. Deep-Sea Res. II 50:2349-2594. 
Livingston, P. A. 
1985. An ecosystem model evaluation: the importance of 
fish food habits data. Mar. Fish. Rev. 47:9-12. 
Livingston P. A., and J. Jurado-Molina. 
2000. A multispecies virtual population analysis of the 
eastern Bering Sea. ICES J. Mar. Sci. 57(2):294- 
299. 
Lorz, H. V., W. G. Pearcy, and M. Fraidenburg. 
1983. Notes on the feeding habits of the yellowtail rock- 
fish, Sebastes flavidus, off Washington and in Queen 
Charlotte Sound. Calif. Fish Game 69:33-38. 
Love, M. S., M. Yoklavich, and L. Thorsteinson. 
2002. The rockfishes of the Northeast Pacific. Univ. 
California Press, Berkeley, CA. 
Mackas, D. L., and M. Galbraith. 
2002. Zooplankton community composition along the 
inner portion of Line P during the 1997-98 El Nino 
event. Prog. Oceanogr. 54:423-437. 
Mackas, D. L., W. T. Peterson, and J. E. Zamon. 
2004. Comparisons of interannual biomass anomalies of 
zooplankton communities along continental margins of 
British Columbia and Oregon. Deep-Sea Res., part II 
Top. Stud. Oceanogr. 51:875-896. 
Mackas, D. L., R. E. Thomson, and M. Galbraith. 
2001. Changes in the zooplankton community of the 
British Columbia continental margin, 1985-1999, and 
their covariation with oceanographic conditions. Can. 
J. Fish. Aquat. Sci. 58:685-702. 
McPhaden, M. J. 
1999. Genesis and evolution of the 1997-98 El Nino. Sci- 
ence 283:950-954. 
