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Sirvi Autor "Ruokonen, Timo J." järgi

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    Diet and trophic niche of the invasive signal crayfish in the first invaded Italian stream ecosystem
    (Nature, 2021) Ercoli, Fabio; Ghia, Daniela; Gruppuso, Laura; Fea, Gianluca; Bo, Tiziano; Ruokonen, Timo J.
    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 ecosystems
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    Introduced alien signal crayfish (Pacifastacus leniusculus) in Finland - uncontrollable expansion despite numerous crayfisheries strategies
    (EDP Sciences, 2018) Ruokonen, Timo J.; Sjövik, Rosanna; Erkamo, Esa; Tulonen, Jouni; Ercoli, Fabio; Kokko, Harri; Jussila, Japo; Centre for Limnology. Institute of Agricultural and Environmental Sciences
    In Finland, massive signal crayfish introductions started towards the end of 1980s, with an estimated total of 2.2 million signal crayfish been stocked before year 2016. During that period, Finnish fisheries authorities have implemented three national management strategies setting guidelines for the crayfish introductions. The main aims of the strategies have been conservation of native noble crayfish stocks and a controlled spreading of the alien signal crayfish within a designated region. In this study, we report the current distribution of signal crayfish in Finland in comparison to the guidelines set in these three national strategies. The present distribution area of the signal crayfish covers most of the Southern Finland. The signal crayfish has been introduced with a stocking permits to over 480 water bodies. In addition, there have been numerous stockings without permits, which are often next to the region designated for signal crayfish. Based on the results, we conclude that crayfisheries strategies adopted in Finland have only had limited effect on the spread of signal crayfish. We presume that main causes for the uncontrolled spreading of the signal crayfish in Finland have been lack of strict official supervision and general lack of awareness about the risks associated with the alien species spreading.
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    Trophic role of marbled crayfish in a lentic freshwater ecosystem
    (Regional Euro-Asian Biological Invasions Centre, 2019) Lipták, Boris; Veselý, Lukáš; Ercoli, Fabio; Bláha, Martin; Buřič, Miloš; Ruokonen, Timo J.; Kouba, Antonín; Institute of Agricultural and Environmental Sciences. Chair of Hydrobiology and Fishery
    Species’ introductions may cause severe adverse effects on freshwater ecosystems and their biota. The marbled crayfish, Procambarus virginalis Lyko, 2017, is an invasive parthenogenetically reproducing crayfish with rapid reproduction, maturation and tolerance to a wide range of environmental conditions, which was introduced to many sites across Europe during the last decade. Due to its recent speciation and limited number of field studies, the knowledge of trophic interactions of the marbled crayfish in freshwater food webs is scarce. An invaded area located in Central Europe was studied to identify the marbled crayfish food web interactions using analysis of carbon 13 C and nitrogen 15N isotopes. This study brings the first insight into the trophic ecology of marbled crayfish in lentic freshwater ecosystems. Algae and detritus were identified as the most important food sources for the marbled crayfish, while zoobenthos and macrophytes were less important. Moreover, the marbled crayfish was found to be an important food source for top fish predators, but marginal for omnivorous fish. Being able to utilize energy from the bottom of the trophic food web, the marbled crayfish may have important roles in the ecosystem, transferring energy to higher trophic levels. It processes allochthonous and autochthonous matter in the ecosystem, thus being a competitor to other organisms with similar food preferences and impacting zoobenthos, algae and macrophytes through predation or direct consumption. To sum up, the marbled crayfish has a strong ability to utilize food sources from different trophic levels, and, thanks to its life history, can be a highly adaptable invader.