The response of Marsh Frog (\kur{Pelophylax ridibundus}) to the presence of alien predators

This study focuses on the antipredator strategies of amphibian larvae in relation to some of their predators. Namely, the relationship between the larvae of the marsh frog (Pelophylax ridibundus) and the invasive species of the fish, the topmouth gudgeon (Pseudorasbora parva). Latter part of the experiment involves investigation into the relationship between another non-native species, the three-spined stickleback (Gasterosteus aculeatus). Both are non-native species of small fishes. The topmouth gudgeon was introduced unintentionally in the 1980s from Hungary. It is listed on the Black List of the Czech Republic and it is on the list of invasive non-native species of the EU Regulation (1143/2014), (Kuřátko, 1998; Poláková et al., 2016). The three-spined stickleback was brought into our territory from America. It was probably released into local ponds by Czech aquarists at the beginning of the 20th century. It is a species that is not listed on the Black List of the Czech Republic, but its negative impact on fish fry has been previously documented (Poláková et al., 2016). Both species have been known for a negative impact on the biological diversity of our fauna, but the influence of these predators on our amphibians has not so far been documented. The experimental part investigates the damage of tadpoles caused by these non-native fishes and the defensive strategy of the tadpoles. The tadpoles were provided with a hiding place as one of the possible escape strategies against the predator