Suitability of fish scales as archive of temporal variations in ambient mercury levels in estuaries

To examine the suitability of fish scales as a historical archive of environmental mercury (Hg) contamination, we analyzed a collection of scales taken from striped bass (Morone saxatilis) captured in the St. Lawrence Estuary between 1944 and 1962. The total mass of Hg in individual scales increases linearly with the weight of the scale, suggesting that Hg is well preserved in the scale tissue. Age, length, and sex of specimens captured during the same year did not significantly influence the concentration of Hg in the scales. The average Hg concentrations in scales of specimens captured in 1956 (53.2 +/- 9.1 ng g super(-1)) and 1962 (58.6 +/- 7.7 ng g super(-1)) are nearly twice as high as in scales from 1951 (30.2 +/- 3.0 ng g super(-1)). These results follow the trend revealed in sediment cores from the St. Lawrence Estuary. A high level of Hg in scales from 1945 (68.7 +/- 18.4 ng g super(-1)) could have been caused by an episode of Hg contamination around 1945 not recorded in the sediment or by a diet-related change in Hg exposure.