Otolith geochemistry is a mainstay of fisheries research, providing individual and population-scale life history information. Oxygen isotopes incorporated into the otoliths from the surrounding water act as proxies for water temperature and can be used alone or in conjunction with trace element data to infer ontogenetic movement. Oxygen isotope data are typically obtained through micromilling otoliths which limits the resolution of the resulting data. Secondary Ion Mass Spectrometry (SIMS) uses ion beams of as little as 5um to obtain a high temporal resolution and allows oxygen isotopes to be studied in much finer detail than previously possible. The pros and cons of SIMS will be discussed and preliminary results from SIMS analysis of two co-occurring species of fishes from the Pilbara will be presented.