Milena Gonçalves-Silva , Elvira D'Bastiani, Thibault Datry, Carla Ferreira Rezende

We investigated predator-prey interactions in the River Tabocas, a non-perennial river (NPR) in Brazil’s semi-arid region, analysing variations between flowing and dry hydrological phases. We analysed predator-prey interactions using fish food items along 1 km of the NPR during flowing (23 sections) and dry (22 isolated pools) phases, identifying 18 predator species and 11 ecological categories of prey. Our results indicate that predators (fish) composition, abundance and environmental variables shift between flowing and dry phases. Despite similar richness, significant differences in fish species composition underscore the importance of temporal fluctuations in predator community dynamics. During the flowing, predator-prey interaction network exhibited a nested pattern. In contrast, the dry phase we observed diverse patterns of predator-prey interaction networks in isolated pools, including nested, modular, specialised, and random structures. Stochastic factors during the dry phase contribute more to the structure of predator-prey network interactions. Predator-prey interactions networks with random structure correspond to isolated pools with fewer predator-prey links and high specialisation rates. Our findings show the importance of identifying priority aquatic refuges to sustain freshwater biodiversity in NPRs. Conservation strategies must account for hydrological variability and stochastic factors to mitigate climate change impacts on the biota of tropical semi-arid NPR.