Unveiling new data on fish parasite diversity in reservoirs of the Brazilian semi-arid

Parasite biodiversity is underestimated or unknown in many regions, yet information on parasites is critical to understanding ecosystem structure and how this will change into the future. Understanding the diversity and role of parasites is especially important in regions exposed to anthropogenic pressures, such as aquatic ecosystems, as their interactions with other stressors can either exacerbate or mediate negative impacts. Water scarcity in the Brazilian semi-arid has led to a proliferation of reservoirs for human use. These artificial waterbodies host a diversity of taxa, including a large number of fish species; however, fish parasite diversity remains undocumented. This study investigated the parasitological diversity of fishes from reservoirs in the Paraíba and Mamanguape River basins in the Caatinga domain, Brazil - one of the most populated semi-arid regions worldwide. Eight reservoirs were studied, with fish sampled across the two phases of the hydrological cycle (dry and rainy seasons) using gillnets, cast nets, and trawl nets. Endo- and ecto-parasites were identified and enumerated, and parasitological indices (prevalence, intensity, and abundance) were calculated. In total, 1,170 individuals of 21 fish species were examined. Of these individuals, 42% were parasitized with at least one of 54 parasite taxa. We recorded 32 new geographical occurrences of parasites and 23 new fish-parasite interactions, expanding our understanding of ichthyoparasite diversity in the Brazilian semi-arid. Moving forward, it is important to develop knowledge around how anthropogenic changes (e.g., biological invasions, climate, and land use change) influence host-parasite structure and dynamics and ecosystem functioning in these ecosystems.