Data describing a predatory fish invasion on a riverine food web

Catfishes are opportunistic feeders that are among the world's worst invasive species. Flathead catfish *Pylodictus olivaris* -- a large predatory catfish -- were first detected in the Susquehanna River, Pennsylvania, USA in 2002. Since then, they established a viable and rapidly growing population that is expanding its range throughout the river system. Although the predatory effects of invasive catfishes on native fish communities have been documented, the effects of invasion on riverine food webs is poorly understood. The goal of this study was to quantify the effects of invasive flathead catfish on the trophic position and isotopic niche space of components of the Susquehanna River food web by comparing invaded and non-invaded sites within the system. This data release is comprised of three .csv files containing data resulting from this study. The .csv file "sia.dat" contains stable isotope data collected from multiple components of the Susquehanna River food web, including primary producers, crayfish, minnows, channel catfish, flathead catfish, and smallmouth bass. Sampling took place during the summers of 2022 and 2023 across predetermined locations along the Susquehanna River, Pennsylvania. The stable isotope ratios in this dataset provide insights into trophic relationships and potential impacts of invasive flathead catfish on the river’s food web structure and energy flow. Data includes stable isotope values of carbon and nitrogen, offering valuable baseline information for ecological analysis and monitoring of invasive species impact. The .csv file "SIA_community_sampling_data_2023.csv" contains community sampling data for a stable isotope analysis of fish collected from the Susquehanna River, Pennsylvania, over the 2022 and 2023 sampling seasons. Each entry includes the date of collection, sampling location, species identification, measurements of length and weight for individual samples, and other notes about the sample if applicable. PFAS Barcode indicates a sample id for a separate project. This dataset does not include flathead catfish. The .csv file "FHC_site_info.csv" contains geographical coordinates for each sampling location associated with the study of flathead catfish (Pylodictis olivaris) in the Susquehanna River. This file includes precise latitude and longitude measurements, allowing for accurate mapping and spatial analysis of the sampling sites. The dataset serves as a foundational reference for understanding the distribution of flathead catfish within the river system and facilitates further ecological assessments and research related to their impact on local food webs.