The concentrations of trace elements followed the order of; Zn≥Cu>As>Cd>Pb>Hg. Elevated concentrations of copper (up to 1010 µg/g) were detected in Ligia from Santa Rosalía (SRo), a locality where industrial mining of copper has historically occurred. Industrial and municipal sewage discharges appear to have contributed to the high concentrations of zinc (326 µg/g) and lead (144 µg/g) found in organisms from Guaymas location. The high mercury concentration in organisms from Mazatlán (M) (2.01 µg/g) was associated with a thermoelectric plant. Natural sources of metals were also detected; coastal upwelling appears to be associated with high cadmium concentrations in Ligia from Punta Baja (PB) (256 µg/g) in the Pacific coast, whereas hydrothermal vents may have contributed to high concentrations of arsenic at Ensenada (E) (61 µg/g).