Public science data suggest that fish is the most important factor in reducing small pond biodiversity in Czechia

A bstract This project tested a public-science approach to the assessment of freshwater habitat quality via simple invertebrate sampling. We combined a mobile phone application and simple instruction to children to sample 50 ponds in Central Czechia, and we analyzed the data using a standard ecological statistics approach. Despite the limitation in scope and taxonomic precision, our data revealed the same patterns as academic studies of the same topic. Specifically, we conclude that the main cause of invertebrate community decline is fish overstocking, while diverse invertebrate communities require aquatic macrophytes. Pollution detectable by children has an effect on invertebrate community structure, but a different effect than fish has, and not as statistically robust. Importantly, almost all large ponds were found overstocked with fish; therefore, they support not more diversity than small ponds, but less, and serve as ecological traps. Our findings suggest that pond conservation should focus primarily on the restoration of aquatic vegetation, and that the most effective approach will be the removal of excessive fish.