Deep-sea skates are among the primary bycatch species in Southern Ocean demersal fisheries, yet their behavioural ecology and three-dimensional space use remain poorly understood due to their inaccessible habitat. This knowledge gap is particularly important because post-release survival in deep-set fisheries can be relatively low, making improved understanding of activity patterns critical for mitigating fisheries-induced mortality. We investigate the free-ranging activity patterns of Kerguelen sandpaper skates (Bathyraja irrasa) using pop-up satellite archival tags (PSATs; n=6) and conventional capture-mark-recapture data (n=291). One PSAT, recovered by chance 5000 km from its pop-up location, provided high-frequency archival data. Conventional tag recaptures suggested that most skates remained within a 36 km radius regardless of time at liberty (2 days to 17 years), though some dispersed up to 175 km. Horizontal movement, modelled with Hidden Markov models under the assumption of close benthic association, indicated an average swim speed of 2.5 km/day (SD = 2.3). Five of six individuals undertook extensive vertical shifts (up to 300 m daily) following bathymetric contours 800–1600 m deep. The recovered archival record revealed repeated alternations between active swimming and rest phases typically lasting 1–2 min, substantially shorter than those reported for other deep-sea skate species. These movement patterns highlight the need for future research to identify high-density aggregation areas to improve bycatch avoidance and inform targeted spatial closures.
Deep-sea sharks play a major role on seamount ecosystems. Yet, knowledge of their diversity and distribution in the Gorringe Bank is scarce. In this study, we use video footage collected using a Remotely Operated Vehicle (ROV) and a tethered camera to investigate the biodiversity of deep-sea sharks in the Gettysburg seamount. Twenty-two individuals from five taxa were observed between 306 and 1714 m deep. The most observed taxa were Galeus sp. inc. with 10 individuals identified during the survey. The knifetooth dogfish Scymnodon ringens and the Portuguese dogfish Centroscymnus coelolepis were also observed and are herein reported for the first time in the Gorringe Bank. Given the conservation status of these species, namely C. coelolepis which was assessed by the IUCN as Endangered in European waters and included in the OSPAR list of threatened and/or declining species, these findings call for enhanced protection measures for this area. The establishment of an offshore MPA in the Madeira-Tore complex appears as the most promising measure to protect and recover the populations of these species in the Gorringe Bank, an important habitat for threatened deep-sea sharks in the Northeast Atlantic Ocean.
This paper presents the results of the analysis of data collected during the first expedition on the “North Pole” Ice-Resistant Self-Propelled Platform (ISP) in the Arctic Ocean in 2022 – 2024. A favorable combination of the drift area and the time permitted to perform hydrographic measurements during the winter season along successive transects crossing the North Eurasian continental slope between Spitsbergen and Franz Josef Land. We were able to trace the spatiotemporal variability of temperature and salinity in the intermediate waters of the Atlantic origin (AW) between the seasonal peaks of warming and cooling, the temporal boundaries of which were established based on historical records from the autonomous moored stations in the 2000s–2010s. Comparison of the hydrographic data with the contact measurements of the ice thickness at the ice testing site adjacent to the ISP allowed us to quantify the impact of the heat flux from the ocean to the ice melt in winter. Based on the established characteristics of the spatiotemporal variability of the AW temperature and long-term satellite time series of the ice area and its extent, we formulated the necessary conditions for the efficient thermal impact of the AW on the ice cover (atlantification) in the western part of the Nansen Basin.
