Diet of the otter Lutra lutra in an almost pristine Portuguese river: seasonality and analysis of fish prey through scale and vertebrae keys and length relationships

摘要: The seasonal diet and size of fish prey the otter Lutra lutra were studied in an almost pristine river North Portugal (Paiva river) through analysis spraints collected during 1 year. To identify Iberian freshwater species (Salmo trutta, Micropterus salmoides, Lepomis gibbosus, Luciobarbus bocagei, Cyprinus carpio, Carassius auratus, Pseudochondrostoma polylepis, Achondrostoma arcasii, Iberocypris alburnoides) consumed by keys based on scales vertebrae first developed tested. Both allowed identification all species, although three Cyprinidae could not be discriminated (P. A. I. alburnoides). Regression equations calculated to estimate dimensions preyed fish. Highly significant linear relationships obtained for standard length versus measurements, except C. carpio. Fish was predominant category autumn winter, but also amphibians, reptiles, mammals, birds, particularly spring summer. In general, high proportions small (3–12 cm indiscriminate Cyprinidae, 3–9 6–12 S. trutta).