Changes in California sea lion diet during a period of substantial climate variability
The California Current Ecosystem (CCE) is a productive eastern boundary upwelling system that supports a wide variety of forage stocks. Decadal and interannual variability in the environment influence forage species, which in turn affects predators. The recent diet of California sea lions (Zalophus californianus; CSL) from Central California was determined using identification of hard parts from scat samples (n = 785) collected on Año Nuevo Island (37.1083°N 122.3378°W) in 2010 and 2012–2016. Comparisons were made with previously reported data from the late 1990’s and with prey availability as measured by fishery-independent surveys. A significant shift in diet was seen between the two decades where diet from the 1990’s was dominated by Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax). By 2010, diet was more diverse, characterized by rockfishes, Pacific hake, and market squid. There were also strong interannual differences in diet during the most recent decade, a time of substantial climate variability in the North Pacific Ocean. In general, prey were consumed in relation to what was available in the environment.
This project was supported with funds from United States Office of Naval Research, Research Opportunity for Program Officers Grant # 12122730. All biological samples were collected in accordance with National Marine Fisheries Service Permits #871851 and #17952. We would like to thank P. Morris at University of California, Santa Cruz, for all her hard work collecting scat samples from Año Nuevo Island, J. Hassrick for his initial project coordination, and M. Hester, R. Carle, and J. Beck at Oikonos for boat support and initial sample collection/processing. Our gratitude goes out to K. Hernandez and interns at Moss Landing Marine Laboratories/San Jose State University and Long Marine Lab/UCSC for their endless hours washing scat samples. We thank D. Crocker at Sonoma State University, B. McDonald at MLML/SJSU, and D. Costa and P. Robinson at LMR/UCSC for lab space needed to process our samples. Finally, we thank all reviewers for their thoughtful comments.
Funding for this study was provided by the United States Office of Naval Research, Research Opportunity for Program Officers Grant # 12122730.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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