DNA taxonomy and barcoding use nucleotide sequence data to achieve comprehensive species descriptions that facilitate reliable species diagnostics and rapid assessment of biodiversity, both of which are of great importance for parasitologists. Such molecular approaches have been applied to the monogenean genus Gyrodactylus, in particular to G. salaris, the cause of serious gyrodactylosis on Atlantic salmon. Here, we discuss, using the example of G. salaris and related species, why DNA barcodes, although powerful for biodiversity assessment, are insufficient to appropriately characterize parasite species--from a parasitological point of view--in the absence of additional data on and infection biology and morphology.