HR: 11:24h
AN: OS22B-05    [Abstracts]
TI: Effects of Climate Change on Sardine Productivity in the California Current System
AU: * Baumgartner, T R
EM: tbaumgar@cicese.mx
AF: División de Oceanología, CICESE, Km 107 Carretera Tijuana-Ensenada, Ensenada, BCN 22860, Mexico
AU: Auad, G
EM: guillo@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD 0224, La Jolla, CA 92093, United States
AU: Miller, A J
EM: ajmiller@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD 0224, La Jolla, CA 92093, United States
AB: The Pacific sardine (Sardinops sagax caeruleus) is one of several coastal pelagic, planktivorous species of fish that provide important trophic links within the ecosystems of the major eastern and western boundary currents. Significant and persistent change in sardine productivity has occurred in the California Current over interdecadal periods in response to reorganization of basin-wide, ocean-atmosphere circulation. Less extreme, but still significant changes in sardine productivity are associated with interannual to decadal-scale climate variability. A precipitous decline of the sardine population began in the mid-1940s with a shift in climate leading to cooling of the California Current system. While the decline, and ultimately the collapse of the population, was exacerbated by intensive fishing, the sardine also suffered a severe reduction in productivity with the southward contraction of favorable thermal habitat that led to restriction of the population to the waters off Southern California and Baja California. This southward displacement resulted in geographic separation of the population from the region off central and northern California that is characterized by significantly higher concentrations of zooplankton that supported the previous levels of success in spawning and larval development. The climate shift in 1976-77 led to the recovery of the population and extension of its range of distribution northwards into the waters off British Columbia. The relation of reproductive success of the sardine population to interannual and decadal climate change was examined for the period 1982-2005 using a suite of seasonal indices representing climate processes and habitat conditions (including zooplankton food levels) occurring through the different stages in the sardine life cycle. We used both stepwise regression and EOF analyses to determine the association between levels of recruitment success and seasonal indices of the Pacific Decadal Oscillation, Ekman pumping (measured at 35°N, 122.5°W), coastal upwelling (at 36°N, 122°W) and zooplankton biomass (represented by values from the center of sardine spawning). The seasonal indices of the PDO are positively correlated with reproductive success, while an inverse relationship between the PDO indices and coastal upwelling is consistent with reduced equatorward flow during coastal warming that favors sardine reproduction. Results also show an unambiguous inverse relationship between Ekman pumping and sardine recruitment success indicating the negative influence of increased offshore transport on the survival of eggs and larvae. There is a surprising lack of association between recruitment success and zooplankton biomass, interpreted to mean that food was not limiting for sardine reproduction during the period analyzed (in the warm regime after 1977). Based on the results of this study, we anticipate that global warming will favor the maintenance of the sardine population over its present range from the Gulf of California into the waters of British Columbia throughout the current century.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4513 Decadal ocean variability (1616, 1635, 3305, 4215)
DE: 4830 Higher trophic levels
DE: 4858 Population dynamics and ecology
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly