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 prediction of biomass consumption (mg), crayfish mortality and survival, and observed and predicted sublethal damage (missing appendages of large crayfish). Our results show that both, small and large topmouth gudgeon individuals were able to consume juvenile crayfish across all size classes. Prey size strongly influenced consumption patterns. Small crayfish were more likely to be fully eaten, whereas medium and large crayfish contributed more to the biomass consumption. In mixed-prey scenarios, larger juveniles were targeted more frequently than smaller ones. Predator size had only a minor effect on overall predation, with small fish consuming slightly more relative to their body mass. Injuries to large crayfish were usually limited to a single appendage, with rare severe multi-limb damage. Fish size did not significantly affect injury frequency. Our results suggest that topmouth gudgeon may affect non-target species, such as crayfish, and indicate that other components of freshwater biota may also be impacted in invaded water bodies. Future activities for topmouth gudgeon regulation should account for population overlaps with endangered or important freshwater species and, if possibly prioritize those localities for regulation.