MEPS 289:285-306 (2005)  -  doi:10.3354/meps289285

Marine mammal occurrence and ocean climate off central California, 1986 to 1994 and 1997 to 1999

C. A. Keiper1,*, D. G. Ainley2, S. G. Allen3, J. T. Harvey4

1Oikonos, PO Box 979, Paradise Valley, Bolinas, California 94924, USA
2H. T. Harvey & Associates, 3150 Almaden Expressway, Suite 145, San Jose, California 95118, USA
3Point Reyes National Seashore National Park Service, Point Reyes, California 94956, USA
4Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California 95039, USA

ABSTRACT: The California Current System (CCS), a highly variable eastern boundary system, supports a rich marine mammal fauna. Variation in local coastal upwelling, coupled with larger scale processes (El Niño/La Niña) affects the productivity and distribution of marine species at all trophic levels. Herein, we present an analysis of the occurrence patterns of marine mammals in the central CCS and relate these patterns to changing ocean climate and prey availability. Data on marine mammal distributions, ocean conditions, and prey availability were collected in waters overlying the continental shelf and slope from Bodega to Monterey Bays, from 1986 to 1994 and 1997 to 1999. Occurrence patterns were investigated using geographical information system (GIS), percent similarity index (PSI), multiple logistic regression, and principal component analyses. Spatial patterns of the most frequently sighted species (California sea lion Zalophus californianus, northern fur seal Callorhinus ursinus, Pacific white-sided dolphin Lagenorhyncus obliquidens, Dall’s porpoise Phocoenoides dalli, harbor porpoise Phocoena phocoena,and humpback whale Megaptera novaeangliae) were related to bathymetry and changing ocean climate, and were likely to have been mediated by changes in prey availability. Temporal changes were related to migration and significant differences in ocean structure resulting from both local and large-scale processes.

KEY WORDS: California Current System · Bathymetry · Cetaceans · Coastal upwelling · El Niño · La Niña · Marine mammals · Ocean habitats · Pinnipeds

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