Diet and trophic niche of the invasive signal crayfish in the first invaded Italian stream ecosystem
Ruokonen, Timo J.
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The occurrence of the signal crayfsh Pacifastacus leniusculus in the Valla Stream was the frst established population of this invasive species recorded in an Italian stream ecosystem. We evaluated the seasonality of diet and trophic niche of invasive signal crayfsh in order to estimate the ecological role and efects on native communities of the stream ecosystem. We studied the diferences in food source use between sexes, life stages and seasons using carbon and nitrogen stable isotope analyses. To supplement stable isotope analyses, we evaluated food source usage using traditional stomach content analysis. We tested the hypothesis that juveniles have a diferent diet, showing diferent trophic niches, compared to adults. Results indicated that signal crayfsh adult and juvenile diets mainly rely on macroinvertebrates and periphyton in summer, shifting to mostly periphyton in autumn. Although the two age classes occupied an equivalent trophic niche, juveniles showed slightly diferent carbon isotope values, suggesting a somewhat ontogenetic shift consistent among seasons. No signifcant diferences were found in adult and juvenile diets between summer and autumn seasons. Our fndings suggest that signal crayfsh juveniles and adults exhibited seasonal feeding habits, probably due to ecological behaviour rather than food resource availability, and that both are likely to impose similar efects on macroinvertebrate communities in this and similar stream ecosystemsTis study was supported by the Estonian Research Council, Mobilitas Pluss research project (MOBJD29 to Fabio Ercoli), the Estonian Ministry of Education and Research (institutional research funding projects IUT 21-2 to Tiina Nõges), the Estonian University of Life Sciences (research project P190254PKKH to Fabio Ercoli) and the European Union H2020 WIDESPREAD (TREICLAKE 951963). Tanks to Dr. Mark J. McCarthy for revising the English of the manuscript.