Experimental evidence simultaneously confirms and contests assumptions implicit to otolith microchemistry research

Otolith microchemistry has become an integral fisheries tool, yet the utility of this tool hinges on the assumptions that (i) elements are temporally stable once deposited in the otolith and (ii) the influence of maternal effects are temporally limited. Here we test these assumptions by quantifying through time the chemical signatures from two families of brown trout (Salmo trutta), differing in maternal life history (i.e., mothers were either anadromous or nonanadromous). Concentrations of zinc, strontium, and barium were temporally stable in the core signatures between different aged siblings, but significant differences in the elemental concentrations of magnesium and manganese were detected. The Sr concentration (indicative of maternal influence) on the growing surface of otoliths converged briefly between families at 3–5 weeks post-emergence, but never stabilized during the course of the experiment. Taken together, these results both confirm and call into question assumptions implicit to otolith microchemistry research. To the extent that the patterns observed here are representative across species, caution is warranted when using otolith microchemistry to address certain types of ecological questions in nature.