Data and code for Tarandek et al. 2026: Topmouth gudgeon as a potential threat to crayfish in ponds

This repository contains the data and code used for the study: Topmouth gudgeon as a potential threat to crayfish in ponds. The provided materials allow full reproduction of analysis and figures presented in the study. Our objective was to investigate the effects of topmouth gudgeon (Pseudorasbora parva) predation on marbled crayfish across different size classes of fish and crayfish. We conducted two experiments: (i) single-size treatment – where crayfish of one size class (small, medium or large) were used per trial, and (ii) mixed-size treatment – where all crayfish size classes (small, medium and large) were present within each trial. In both experiments, two predator size classes (small and large) were used. Each experiment consisted of 10 trials per size of predator and prey along with negative controls. Each trial was conducted over a 48-hour period. The analyses focus on crayfish consumption (mortality) and sublethal damage (missing appendages) using binomial generalized linear mixed models. Our results demonstrate that both small and large topmouth gudgeon consumed juvenile marbled crayfish across all tested size classes. Predation probability was strongly influenced by prey size, with small crayfish being consumed significantly more frequently than medium and large individuals in both experiments. Predator size did not significantly affect the probability of crayfish consumption or the frequency of non-lethal injuries. Among surviving large crayfish, appendage damage was common but was usually limited to the loss of a single appendage. Our findings identify a previously undocumented trophic interaction between two widespread invasive freshwater species. Although the experiments were conducted under controlled laboratory conditions, the results demonstrate that topmouth gudgeon can act as predators of juvenile crayfish and suggest that similarly sized freshwater organisms may also be vulnerable to predation. Additional field and mesocosm studies are needed to determine how frequently these interactions occur under natural conditions and whether they influence recruitment or population dynamics.