MEPS 473:261-273 (2013)  -  DOI: https://doi.org/10.3354/meps10063

ABSTRACT: We present a novel approach to examine the relationship between pelagic juvenile fish and their environment in an open coastal system using a geospatial technique to relate water and otolith chemistries. We compared the chemistries of water and pelagic juvenile rockfish otoliths Sebastes jordani collected from a coastal upwelling system off central California during May and June 2009. To determine the presence and composition of an upwelling chemical signature, the elements Ba, Sr, and Mg expressed as ratios relative to Ca were quantified in the water and outer otolith margin using inductively coupled plasma mass spectrometry. Recently upwelled water, as indicated by a strong inverse relationship with water temperature, had an elevated Ba:Ca concentration. Using all 3 element ratios, cluster analysis and multivariate analysis of variance were used to identify 3 distinct chemical signatures for otolith and water samples. When mapped, these signatures displayed marked geospatial variability that we attributed to mesoscale upwelling dynamics. Canonical discriminant function analysis results indicated that the relative contribution of each element to the 3 signatures was similar between water and otoliths. Interestingly, otoliths containing upwelling signatures (high Ba:Ca) did not match spatially with upwelling signatures in the water. A directional-dependence analysis (spatial cross-covariance) revealed the highest covariance between water and otolith chemistries at a distance between 50 and 100 km apart, suggesting southern movement or transport of fish.

KEY WORDS: Upwelling · Central California · Barium · Multivariate statistics · Geospatial statistics · ICP-MS