This data set has biological measurements and stomach content analysis for fourteen specimens of Centrolophus niger which were frozen whole at sea during the Icelandic part of the International Ecosystem Summer Survey in Nordic Seas (IESSNS) in July 2017 and July 2021. In 2017, three specimens were collected to confirm species identification by a specialist at home institute. In 2021, all caught specimens were collected for detailed biological study. The C. niger were by-catch in a scientific pelagic ecosystem survey which includes trawling, cod-end mesh size 50 mm, in the surface layer, trawl headline visible in surface and foot rope at approximately 35 m depth. For detailed information about the surveys see the cruise reports attached to the campaigns. The data is provided by the Marine and Freshwater Research Institute (MFRI) in Iceland.