Comparative study on trace metal accumulation in the liver of two fish species (Torpedinidae): concentration-size relationship.

Metal concentrations (Hg, Cd, Pb, As, Cr, Cu, Zn and Ni) were measured in the liver of two fish, Torpedo nobiliana (electric ray) and Torpedo marmorata (marbled electric ray), from the Mediterranean Sea in order to comparatively investigate their current pollution status. Maximum mean levels of Hg were detected in electric ray (mean: 2.16μgg-1 ww), while marbled electric ray accumulated especially Cd (mean: 0.06μgg-1 ww), Cu (mean: 3.83μgg-1 ww) and As (mean: 32.64μgg-1 ww). The metal concentrations are similar to those reported in literature, except for Cd, As and Ni. Hg concentrations increased with increasing fish body length in both species, whilst no significant concentration-size relationship was found for other metals. To the best of our knowledge this is the first report providing information on trace metal levels and relationship between concentration and size of these cartilaginous fishes. Future studies on the concentrations and effects of environmental contaminants in various torpedinid species are surely needed.