Raw data obtained from stable isotope analysis of δ13C and δ15N in beaks of the squids Gonatus fabricii (Lichtenstein, 1818) and Todarodes sagittatus (Lamarck, 1798) (Cephalopoda: Oegopsida), and primary analyses of these data. Squids sampled in the Baffin Bay, Davis Strait and Nordic Seas (1882-2010) and Iceland, Faroe Islands and Ireland (1844-2023), respectively. The beaks either come from the squids caught as bycatch, or from natural history museums, from stomach contents of predators.

Gonatus fabricii (Gonatidae)Time series; Year; n squids; Area; SourceLate XIXth C.; 1882; 1; Baffin Bay; BycatchLate XIXth C.; 1891; 1; ---; ---;1990s; 1900; 9; Nordic Seas; Northern fulmar's stomach contents1930s; 1930; 2; Davis Strait; Sleeper shark's stomach contents1930s; 1936; 5; Baffin Bay; Bycatch1970s; 1975; 5; ---; Bycatch1970s; 1977; 2; ---; Bycatch1970s; 1979; 2; ---; Bycatch2000s; 2004; 10; ---; Bycatch2010s; 2010; 10; Nordic Seas; Sperm whale's stomach contentsTodarodes sagittatus1840s; 1844; 4; Faroe Islands; Long-finned pilot whale's stomach contents1880s; 1881; 10; Iceland; Long-finned pilot whale's stomach contents1890s; 1897; 10; Faroe Islands; Long-finned pilot whale's stomach contentsContemporary 2016; 1; Ireland; BycatchContemporary; 2017; 1; Ireland; BycatchContemporary; 2018; 1; Ireland; BycatchContemporary; 2023; 4; Ireland; Bycatch