Study area and sample collection

The stomach contents of 159 TOA individuals were analyzed from catches made by the Ukrainian commercial vessel Calipso in Subarea 48.1 (northern tip of the Antarctic Peninsula, Fig 1). Fishing operations were carried out in February 2020 (n = 89 stomachs) and February 2021 (n = 70 stomachs) using spanish bottom longlines at depths between 924–1560 meters in 2019/20 and between 1075–1371 meters in 2020/21 (S1 Table). The squid Dosidicus gigas (cut into rectangular pieces) was used as bait, and therefore were not considered in the subsequent stomach content analysis. Each TOA individual was weighted (in grams, g), sexed and sized (total length in cm) onboard. Extracted stomachs were stored frozen at -20°C and sent for analysis to the Bioresources Laboratory of the Chilean Antarctic Institute (INACH) in Punta Arenas, Chile.

Boxes show CCAMLR research blocks 48.1_1 (red) and 48.1_2 (yellow), explored by the Ukrainian research program during fishing seasons 2019/20 and 2020/21. Map created in ArcMap 10.8.2 (https://www.esri.com/), using the online Ocean Basemap (https://www.arcgis.com/;itemid=5ae9e138a17842688b0b79283a4353f6). Subarea 48.1 and research blocks shapefiles downloaded from the CCAMLR geographical data available on github (https://github.com/ccamlr/data/tree/main/geographical_data).