The impact of introduced Ponto-Caspian mysids (Paramysis lacustris) on the trophic position of perch (Perca fluviatilis) in European mesotrophic lakes.
Paramysis lacustriswas introduced into Lithuanian lakes in the middle of the 20th century. It was assumed that P. lacustriswill enhance efficiency of primary production utilization and channelling of primary production towards higher trophic levels, i.e. commercially important fish species. However, at the time of P. lacustrisintroduction, there were no reliable data about its trophic position in lakes. Thus, P. lacustriswas considered to have no or little impact on native ecosystems. Until now, there is a gap in the knowledge of the trophic role and potential impacts of P. lacustrison local food webs in lakes. Here we investigated the impact of P. lacustrison the food chain length of its potential predator Perca fluviatilis in temperate lakes. In this study, gut contents and stable isotope analyses were performed to assess the diet and trophic position of P. lacustrisand P. fluviatilis in lakes with and without invasive mysids. The results obtained revealed that P. lacustrisconsumes a significant amount of animal prey and occupies the third trophic level in lake littoral zones. Furthermore, our results showed that P. lacustrismight enhance the food chain length for at least some zooplanktivorous fishes. Overall, the assumption that P. lacustrisinvasion has no whole-ecosystem consequences, as it was thought before its introduction, is not correct.