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Marine Ecology Progress Series

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MEPS 418:213-222 (2010)  -  DOI:

Complexity of domoic acid-related sea lion strandings in Monterey Bay, California: foraging patterns, climate events, and toxic blooms

Sibel Bargu1,*, Mary Silver2, Tracey Goldstein3, Kathryn Roberts2, Frances Gulland4

1Department of Oceanography and Coastal Sciences, School of the Coast and Environment, 1235 Energy, Coast & Environment Building, Louisiana State University, Baton Rouge, Louisiana 70803, USA
2 Department of Ocean Sciences, Earth and Marine Sciences Building, A-312, University of California, Santa Cruz, California 95064, USA
3Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, California 95616, USA
4The Marine Mammal Center, 2000 Bunker Road, Sausalito, California 94965, USA

ABSTRACT: The neurotoxin domoic acid (DA) produced by the diatoms Pseudo-nitzschia has been responsible for deaths of marine mammals and birds in Monterey Bay, California, USA. In this study we examined links between DA-related strandings of the seasonally migratory California sea lion Zalophus californianus and regional occurrences of DA-producing diatoms using a decade-long time series. Results suggest a more complex pattern of stranding than anticipated, one not related simply to regional abundance of the toxin producers. Stranding patterns of sea lions exhibiting signs of acute DA toxicosis may be best explained by multiple causative factors including timing of toxic blooms with respect to the sea lion breeding cycle, adequacy of sea lion prey during the breeding season, as well as the geographic range of this pinniped outside of the breeding season. Three DA-related stranding events occurred in Monterey Bay in 1998, 2000 and 2007, when toxic DA blooms were present in the Bay and the California coast was experiencing El Niño/Southern Oscillation conditions. Foraging centers near the breeding site likely provided inadequate food for individuals, leading to northerly movement of these highly mobile predators to other geographic sites resulting in exposure to toxic DA-producing blooms. High toxic Pseudo-nitzschia and DA concentrations did not, however, result in DA-related stranding events in 2002, 2003 and 2004, when weaker than normal upwelling events were present in the Bay. Relative productivity of central versus southern California with respect to the breeding season thus appears to strongly influence the frequency of DA-related strandings in Monterey Bay, California.

KEY WORDS: California sea lion · Harmful algal blooms · Animal stranding · Foraging behavior · Domoic acid · Pseudo-nitzschia · ENSO · Monterey Bay

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Cite this article as: Bargu S, Silver M, Goldstein T, Roberts K, Gulland F (2010) Complexity of domoic acid-related sea lion strandings in Monterey Bay, California: foraging patterns, climate events, and toxic blooms. Mar Ecol Prog Ser 418:213-222.

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