Natal trace-elemental signatures in the otoliths of an open-coast fish

We show that chemical differences found along the open coast are sufficiently strong to leave a readable natal signature in fish otoliths. Laser ablation inductively coupled plasma mass spectrometric (LA-ICPMS) analysis of individual larval otoliths taken from near-term females of the primitively viviparous rockfish Sebastes atrovirens indicates detectable levels of several trace elements. Although these larvae show considerable between-brood differences in elemental concentrations for females taken at the same site, there was significant between-site discrimination of natal signatures for regions only tens of kilometers apart in the waters off of Santa Barbara, California. For several (but not all) elements, differences between regions were consistent between 2 yr. We also explore three different possible proxies (edges of otoliths of adult fishes, resin-based elemental accumulators, and samples of seawater) that might be used to predict geographic differences in natal signatures. Although these proxies all showed significant regional differences in the concentration of some elements, only manganese showed some congruency in the spatial patterns seen in the larval otoliths. Consequently, currently available proxy measures cannot accurately predict the elemental composition of otolith cores.