Environmentally Induced Variation in Elemental Composition of Red Drum (Sciaenops Ocellatus) Otoliths

Diet, temperature, and salinity were manipulated to determine their influence on magnesium, potassium, strontium, sodium, and calcium concentrations in sagittal otoliths of red drum, Sciaenops ocellatus, using an atomic absorption spectrophotometer and wavelength-dispersive electron microprobe. The experiments were designed to determine whether environmental history could be reconstructed from otolith microchemistry, and to assess the potential for confounding factors. No dietary effect was detected on whole otolith elemental composition at a salinity of 30‰, although an effect at very low salinities is expected. Levels of calcium, strontium, and potassium in whole otoliths were correlated with temperature, and sodium was correlated with salinity. Despite highly significant correlations (P ≤ 0.01), there was a high degree of variation in concentrations of each element within individual otoliths, even though they were produced under constant conditions. This suggests that precise reconstruction of environmental history for young red drum is impractical using otolith elemental composition.