The chemical composition of fish scales has been reported to reflect the composition of the waters in which fish have been resident, therefore having the potential for the assessment of temporal trends in watershed water quality. Here we studied the historical (1983-2007) metal contamination in the Ulla river (NW Iberian Peninsula) watershed - impacted by a Cu mine that was in operation from 1973 until 1988 - by means of the analysis of major and trace elements in salmon scales. Results indicate the presence of a significant contamination for several metals (especially Cu, Au, Ag, Sb, Zn) during the 1980's. Concentrations of Cu in salmon scales during the influence of the mine (1983-1990) were 20 ± 5 μg/g, exceeding the values for the recent years (1995-2007): 1.8 ± 0.4 μg/g. Concentrations for Au in these two periods were 31 ± 12 and 2.1 ± 1.2 ng/g; for Ag: 21 ± 4 and 4 ± 2 ng/g; for Sb: 48 ± 21 and 15 ± 4 ng/g; and for Zn: 133 ± 16 and 93 ± 10 μg/g. The estimated concentrations of dissolved copper during the operation of the mine indicate a scenario of toxic effects due to sensory impairments in the salmon, and a reduction in scales calcification. The results presented here demonstrate that the analysis of trace elements in archived fish scales is a suitable tool for the reconstruction of the past contamination in aquatic systems, and it can be also used as a non-lethal approach for biomonitoring purposes.
Keywords: Contamination; Fish scales; Metals; Mine; Salmon.
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