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

Abstract

Background. The twaite shad, Alosa fallax (Lacépède, 1803), is a migratory marine species which lives in North Atlantic and sporadically appears in the Baltic Sea. Parasites of the twaite shad are poorly known, especially those infecting the fish occurring in the Baltic. Materials and methods. Within 2003–2005, 100 individuals of A. fallax, caught in the southern Baltic, were examined for the presence of parasites following commonly used procedures. Results. The parasites found represented Digenea: Diplostomum spp. and Nematoda: Contracaecum osculatum (Rudolphi, 1802), Hysterothylacium aduncum aduncum (Rudolphi, 1802), and Desmidocercella numidica (Seurat, 1920). The overall prevalence was 74.0%, while mean intensity averaged 10.5. The most frequent parasites were Diplostomum spp. (62.0 %, 10.5) and C. osculatum (39.0%, 2.2). This study constitutes the first record of Diplostomum spp., C. osculatum, and D. numidica in twaite shad. Conclusion. The parasite fauna of the twaite shad from the southern Baltic Sea is poorly diversified, but the intensity and prevalence of infections are relatively high.

Keywords

• twaite shad
• Alosa fallax
• parasites
• Baltic Sea