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The elemental composition of fish otoliths may represent a permanent record of the environmental conditions an individual has experienced as trace elements, incorporated into the growing surface of the otolith, reflect the physical and chemical characteristics of the ambient water. We tested the utility of trace element signatures in otoliths as natural tags of the river of origin of juvenile American shad (Alosa supidissima) collected from the Connecticut, Hudson and Delaware Rivers in August and October 1994. Four elements (K, Mn, Sr, and Ba) showed significant variability among sites within rivers in August, although only Mg showed a significant site effect by October. Four elements (Mg, Mn, Sr, and Ba) differed significantly among rivers in both months. Linear discriminant functions based on the trace element signatures classified fish to their natal river with -90% accuracy in both August and October collections. The discriminant function generated from the August data was able to classify fish collected in October successfully with better than 80% accuracy. On the basis of our findings, the river of origin of adult fish could be accurately determined by quantifying the trace element composition of the juvenile portion of their otoliths.

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Arsenic(lll), As", monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) and arsenobetaine (AsB) were separated by high-performance liquid chromatography (HPLC) and determined on-line by inductively coupled plasma mass spectrometry (ICP-MS). Two forms of HPLC were used: ion pairing and ion exchange, with absolute detection limits for arsenic ranging between 50 and 300 pg. These detection limits were independent of the arsenic species when peak area was used for quantification. Anion pairing was found generally to be more sensitive to changes in the matrix of the sample injected. Anion exchange was more tolerant because of the higher buffering capacity of the mobile phase. Cation pairing was found suitable for the determination of DMAA and AsB in a biological sample containing high concentrations of salts.

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