Sardine biomass is poorly correlated with the Pacific Decadal Oscillation off California

Abstract

Pacific sardines (Sardinops sagax) fluctuate widely in abundance over interannual to multidecadal time scales. For Pacific sardines, there have been repeated attempts to link fluctuations in biomass to indices of climatic variability, such as the Pacific Decadal Oscillation (PDO). Correlations between the PDO with periods of 40-76 years, and sardine biomass with periods of 40-70 years, have been inferred using 90-year time series (e.g. 1920-2010). The inferred correlations cannot be tested because the long-period fluctuations are outside the observation window that can be analysed statistically, i.e. the period (40-76 years) is greater than half the length of the series (45 years). To date, there has been no attempt to test the relationship between lowfrequency fluctuations of sardine biomass and the PDO using longer paleoclimatic time series proxies for sardine biomass and the PDO. Here we use a 370-year record of paleoclimatic proxies to show that fluctuations in sardine biomass off California are not related to the PDO, despite the appearance of correlation in the 90-year record from 1920 to the present day. © 2012. American Geophysical Union.