Parvalbumins are acidic calcium-binding proteins found in large quantities in the white muscle fibers of cold-blooded vertebrates. Fish display two to seven parvalbumin isotypes that are species specific and thus constitute a valuable tool in the study of phylogenetic relationships, and as a specific biomarker for fish identification. Parvalbumins were isolated from a selected sample of marine teleosts and elasmobranchs. Purified isotypes were characterized via HPLC (gel filtration, and ion exchange), and electrophoresis (IEF, and SDS-PAGE). An indirect immunoassay was developed for the parvalbumin isotypes using monoclonal antibodies directed against the highly conserved calcium-binding site. Parvalbumins from selected fish species are compared and contrasted by standard biochemical and immunological methods.