River valleys, apart from their natural values, have unique visual features. The perception of landscape is mainly determined by its spatial structure. Contemporary scientific research confirms significant compliance in the terms of ecological and aesthetic evaluations. The paper presents the results of the research carried out by the authors in the Valley of Samica Kierska River in Wielkopolska which is an area protected as a part of Natura 2000 network. There were three main objectives of the research: 1) an analysis of the relations between spatial structure and visual perception of landscape in the Valley of Samica Kierska River, 2) a comparison of the expert evaluation of the visual values with public aesthetic preferences towards landscape, 3) an assessment of the potential effectiveness of the existing conservation methods in Natura 2000 network for the preservation of landscape visual features.
Background. The twaite shad, Alosa fallax (Lacepčde, 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 numidia (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 rekord 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.