Eurasian otter Lutra lutra diet mirrors the decline of native fish assemblages in a semi-arid catchment (River Segura, SE Spain)

Abstract In semi-arid environments, the effects of irregularly distributed rainfall, flow regulation and water inter-basin transfer enhance spread non-native fish to detriment native communities. River Segura, since 1980s number species has progressively increased, also because building facility connecting rivers Segura Tajo. With aim highlighting how man-driven changes in diversity communities affect diet top-predators, we compared Eurasian otter Lutra lutra span 20 years, i.e. 1997–98 vs. 2016–19. As habitat quality affects condition Andalusian barbel Luciobarbus sclateri , most widespread fish, size preyed barbels point out whether human activities may have lowered their profitability otters. Fish introduced red swamp crayfish Procambarus clarkii formed bulk both study periods. 2016–19 contribution increased significantly, for which included ten species. Otter feeding habits faithfully mirrored variation composition community confirmed importance as alternative-to-fish prey Iberian Peninsula. The average length was significantly lower second period, consistently with a decline