Diet of the introduced pikeperch Sander lucioperca (L.) (Osteichthyes, Percidae) in a recent colonised reservoir in south-western Iberian Peninsula

摘要

The present study examines the diet of pikeperch (Sander lucioperca) in Iberian freshwaters. Food habits of Sander lucioperca were studied based on stomach content analyses of 376 specimens (12.22-52.52 cm total length) collected in 2009 on a south-western Iberian reservoir. A total of 265 stomachs (79.52%) contained food, and fifteen taxonomic levels of prey were identified. The most important prey was fish according to the Relative Importance Index (IRI). Trophic level analysis revealed that 5. lucioperca is a top predator throughout its life history. There were no differences between sexes (p = 0.573, ANOSIM) and seasons (p = 0.266) in the diet composition, but minor dietary shifts with ontogeny were found. The Levins' standardized index indicated wider niche breadth for small pikeperch, whereas larger pikeperch specimens showed a narrow niche breadth with a specialization in congeners. The graphical analysis (Amundsen method) of the diet confirmed that pikeperch feed mainly on congeners in Alcantara reservoir; however some native species were also consumed.