Helminth parasites of twaite shad, <I>Alosa fallax</I> (Actinopterygii: Clupeiformes: Clupeidae), from the southern Baltic Sea

The twaite shad, Alosa fallax (Lacepede, 1803), is a migratory marine species that ascends rivers to spawn. The species occurs in the North-East Atlantic from Scandinavia to the coasts of Morocco; it is also found in the Mediterranean and Black Seas and sporadically appears in the Northand Baltic Seas. In addition, there are lacustrine populations of this fish in Italy and southern Ireland. The systematics of the twaite shad is uncertain. Mentioned in the literature sub-species of A. fallax shall be often considered as ambiguous synonyms (Quignard and Douchement 1991, Froese and Pauly 2008). Very little is known about the occurrence of parasites in the twaite shad or on their impact on the species. Parasites of A. fallax from the southern Baltic had been studied only occasionally (Nybelin 1922, Hartwich 1975, PileckaRapacz 2003). The present paper reports on the occurrence of parasites in twaite shad in southern Baltic.