This dataset contains measurements of stable isotope ratios of carbon and nitrogen made in 580 samples of diadromous fauna (459 individual specimens belonging to 14 taxa) and their food items (121 samples of drifting particulate organic matter, leaf litter or biofilm). Samples were taken in 3 rivers of Guadeloupe (French West Indies) between February and May 2017. In each river, 3 stations were sampled: one upstream from a water extraction dam, one downstream from each dam, and one at the mouth of the river. Analytical measurements were performed at University of Liège (Belgium)’s stable isotope facility (Laboratory of Oceanology, Stable Isotope in Environmental Sciences and Trophic Ecology workgroup, https://www.oceanobio.uliege.be/). More info about the studies and sample preparation can be found in the publication referenced below. The dataset consists of two files: one containing the data itself, and one describing all used terms (measurements or metadata, derived from Darwin Core standards, https://dwc.tdwg.org/terms/).