Oscillatory zinc distribution in Arctic char ( Salvelinus alpinus) otoliths: : The result of biology or environment?

Scanning proton microprobe (SPM) analysis and imaging was used to map the distribution of zinc in otoliths of anadromous and non-anadromous Arctic char ( Salvelinus alpinus) from the Canadian Arctic. Zinc distribution patterns were oscillatory with concentrations ranging from 35 to 240 ppm. Superimposition of the zinc distribution on optical images of the otoliths permitted correlation of zinc uptake with annular structure in the otoliths and with strontium patterns from the same otolith. Well defined oscillations of zinc concentrations were observed in the otoliths, particularly in the first few years in all samples. In anadromous fish, these overlapped with the onset of the strontium oscillations that were indicative of anadromy and then declined; in non-anadromous fish the oscillations generally continued to later years. Oscillatory zoning of zinc may indicate: (1) variations in the concentration of zinc in water; (2) variations in nutrient availability in the environment; (3) temperature variations in the habitat occupied; or (4) a combination of zinc concentration, nutrient availability or temperature changes. As such, the systematic distribution of zinc in otoliths has the potential to provide temporally constrained information on fish habitat and/or fish biology.