Predicting the effects of reintroducing a native predator (European eel, Anguilla anguilla ) into a freshwater community dominated by alien species using a multidisciplinary approach

摘要

Multiple introductions of alien species can lead to the formation of new and diversecommunities with diverse interactions, particularly in isolated freshwater ecosystems.In Lake Arréo (currently known as Caicedo-Yuso), located in Basque Country,Northern Spain, the introduction of several North American species (largemouthbass Micropterus salmoides, pumpkinseed Lepomis gibbosus and the red swampcrayfish Procambarus clarkii) and the common carp Cyprinus carpio has resultedin a unique community composed mainly of alien species. Previous efforts toeradicate them by intensive fishing/trapping have failed. Reintroduction of nativepredators could represent a complementary method, with an added biodiversityvalue. The reintroduction of the European eel Anguilla anguilla could lead to anincreased predation on crayfish as shown by previous studies, but also affects theabundance of juvenile fish. To investigate the current situation of Lake Arreo,stable isotope analyses were conducted using 15 muscle tissue samples per each fishand crayfish species, while stomach contents of the same species were analysed.Additionally, samples from the common reed Phragmites australis, the trophicallylowest food source available for fish and crayfish species, were collected and usedas baseline for the isotope analysis. To investigate the usefulness of stable isotopesto predict the effects of species reintroductions on present species communities,available stable isotope and diet data from A. anguilla in a German freshwater lakewith a similar species composition were retrieved and included in the Arreocommunity analysis. While results from both, dietary and stable isotope analyses,indicate high interactions among alien species with P. clarkii having a centralposition, the modelled reintroduction of A. anguilla shows to possibly affectrecruits of alien fish species as well as an increased feeding of M. salmoides onreintroduced eels.