A 500 year climate catch: Pelagic fish scales and paleoproductivity in the Santa Barbara Basin from the Medieval Climate Anomaly to the Little Ice Age (AD 1000-1500)

Based upon observations from the 20th century, populations of lower trophic level, short-lived fish species are thought to be controlled by large scale ocean-atmosphere circulation shifts. Here, we provide a new 500 year reconstruction of northern anchovy and Pacific sardine fish scale deposition rates (SDRs) and relative abundance from Santa Barbara Basin (SBB), through the transition from the Medieval Climate Anomaly into the Little Ice Age (AD 1000-1500). Three intervals of high anchovy biomass (high SDRs) were coincident with increased upwelling diatom abundance in SBB and cool/negative Pacific Decadal Oscillation (PDO) events at 1130-1160, 1280-1310 and 1410-1450. Intervals of absent or low SDR of both sardine and anchovy in SBB sediments occurred in association with increased wave activity (benthic diatoms), California Current diatoms, and the relative dominance of sardine over anchovy. Thus although ocean-atmosphere circulation shifts such as the PDO appear to play a role in shifting the dominance of anchovy over sardine, the biomass of sardines as indicated by SDRs has a more complicated response to environmental change.