This dataset contains the values of natural abundance of stable carbon and nitrogen isotopes in bulk muscle and gut contents, and nitrogen isotopes in muscle amino acids measured in 1801 samples of 10 small pelagic fish species sampled during the PELACUS spring cruises in the northwestern Iberian shelf and in adjacent waters of the southern Bay of Biscay. Length, weight, sex and maturity stage data for each individual analyzed are also provided. Fishes were collected by midwater trawls of ca. 30 m2 pelagic net equipped with a graded-mesh netting (starting with 30 mm and ending with 4 mm). The duration of each trawl was between 25 and 40 min. Different species occurred in the same trawls. Samples of muscle tissue and gut contents were preserved dried (50°C, 48 h) or freeze-dried. No treatments for lipid removal were used prior to carbon analyses. Stable isotope determinations in bulk samples (also carbon and nitrogen contents) were made by isotope-ratio mass spectrometry coupled to an elemental analyzer (Bode et al. 2018). Stable nitrogen isotopes in amino acids were determined by isotope-ratio mass spectrometry couples to a gas chromatograph (Bode et al., 2021).

Data was additionally funded by PELACUS (1998-1999) project.