Deep-sea skates, among the most abundant bycatch in Southern Ocean demersal fisheries, face heightened susceptibility to fishing pressure due to their life history characteristics. In longline fisheries targeting Patagonian toothfish, skates caught in good condition are released; however, their post-release survival remains unknown but is expected to be low, given the extreme capture depths (>1000m). Post-release survival rates are essential to determine an acceptable population persistence for a sustainable fishery. During a 2023 Kerguelen Plateau fishing voyage, 24 pop-up satellite tags were deployed on Bathyraja irrasa for 30-day investigations into post-release survival and free-ranging activity patterns. Post-release survival was assessed using a Hidden Markov Model (HMM) applied to tag mobility data, revealing a 29% survival rate. Vertical migrations within depth time series data further supported this finding. Finally, most likely paths between release and pop-up were estimated using another HMM based on presence absence likelihood rasters applied to depth time-series and bathymetry, supposing skates stayed relatively close to the sea floor. Most surviving skates likely stayed close to their release location, although one travelled over 120km. The identified low survival rate prompts a review of skate bycatch management strategies in Southern Ocean demersal fisheries with high release rates.