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New Study to Explain Cause of Seabird Die-Offs
POINT REYES - Although 2005 was not an El Nino year, oceanographic conditions off the U.S. West Coast last spring were reminiscent of the physical and biological changes that occur during El Nino events.
A Cassin's auklet that flew aboard the R/V McArthur II. Credit: Benjamin L. Saenz of PRBO. |
Unusually weak winds, warmer than normal ocean temperatures, suppressed coastal upwelling, low primary productivity, and the northward migration of warm-water species such as albacore and Humboldt squid - all these occurred last year.
Krill, tiny shrimp-like organisms, at the base of the food chain. The species in the photo are about ½-inch long. Credit: Benjamin L. Saenz of PRBO. |
Of particular note were mass die offs of several species of seabirds and the complete reproductive failure of Cassin's auklets on California's Farallones Islands. The entire colony of Cassin's auklets abandoned their nests last May, most likely because breeding pairs could not find krill, their main food.
A series of research cruises, funded by California Sea Grant and to begin in March, will help researchers identify the physical processes that created El Nino-like conditions that ultimately led to starvation of seabirds and reduced abundances of other animals, including "young of the year" rockfishes and Coho salmon.
Marine biologists from PRBO rinsing nets after capturing krill at the shelf-break near the Farallon Islands. Credit: Sophie Webb of PRBO. |
More specifically, investigators will seek to identify the chain of events that suppressed coastal upwelling, the process by which nutrients are brought to the surface. The seasonal injection of these nutrients supports the growth of small organisms at the base of the food chain, including krill. Surveys suggest that krill abundances in 2005 were about half of what they were in 2004. The scientists want to know how this significant but not catastrophic reduction in available food was amplified to higher trophic levels at such unprecedented scale. Their findings will provide insights into climate variability, climate change and its relevance to ecosystem-based fisheries management. By offering insights into the potential effects of large climatic variability, the scientists hope that fisheries managers will be able to ensure protection of seabirds and other species that may or may not be commercially targeted during times when food is scarce.
NOAA's California Sea Grant College Program is a statewide, multi-university program of marine research, extension services, and education activities administered by the University of California. It is headquartered at Scripps Institution of Oceanography at the University of California, San Diego. The National Sea Grant College Program is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.
Investigators on the project:
William J. Sydeman,
Director, Marine Ecology Division
PRBO Conservation Science
T. 415-868-1221 Ext. 319
Jaime Jahncke,
Senior Scientist, Marine Ecology Division
PRBO Conservation Science
T. 415-868-1221 Ext. 335
John Largier
Bodega Marine Lab
University of California, Davis
T. 707-875-1930
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