Quantifying post-release survival of skate bycatch in the HIMI Patagonian Toothfish longline fishery

Skates (Rajidae) are commonly taken as incidental bycatch in demersal longline fishing operations throughout deep waters of the Kerguelen Plateau. Due to their life history characteristics of slow growth and late maturation, their populations are particularly vulnerable to fishing mortality which can lead to overall and localised population declines. At Heard Island and McDonald Islands (HIMI), Kerguelen Sandpaper skates Bathyraja irrasa make up a high proportion of the biomass of bycatch in the Patagonian toothfish (Dissostichus eleginoides) fishery operating within Australian EEZ waters. Currently, only retained skates are counted towards fishery removals, but the overall fishing-induced mortality may be higher. This project aims to inform post-release survival rates using pop-up satellite tags and investigate capture-related stress through blood biomarkers. The incorporation of post-release survival estimates into the skate bycatch assessment allows for a more realistic estimate of sustainable yield.