Development Of A Paleo Forage Fish Index and Comparison Of Multiple C
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Authors
Filardo, Alexander Dominic
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Marine Science
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Abstract
Evidence from both fossil fish scale records and surveys of fish abundance suggest that small pelagic forage fish abundances in the California Current Ecosystem (CCE) have been declining since the late 20th century, however, the low values in the 1900s have never been put into the context of long-term records. This study compiled scale fluxes from sardine, anchovy, hake, and myctophid as well as a novel record of skeletal debris from three kasten sediment cores as well as numerous box core records from the Santa Barbara Basin (SBB) to develop a Paleo Forage Fish Index. The Paleo Forage Fish Index, which is a normalized compilation of the five time series, revealed periods of extended negative anomalies beginning around the 1930s and from the 1960s to the end of the record following a shift in plankton assemblages toward subtropical taxa, which suggests that the 20th century warming trend influences the abundance, distribution, and/or species assemblage of small pelagic forage fish in the CCE. In addition, this study developed a rigorous outlier detection procedure and determined that up to 30% of the sampling intervals contain identified outliers, although the presence of outliers do not have a major effect on the overall nature of the records. Comparison between cores shows significant differences between kasten cores and between composite core records, which emphasizes the need for a multi-core, composite record to average out decadal to interdecadal scale differences between cores. Furthermore, the skeletal debris record was determined to be a compilation of multiple species with vertebrae primarily coming from fish between two and eight centimeters in length.
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Hawaii Pacific University