Spatio-temporal variability of Nephrops norvegicus density distribution on the Aran grounds and its implications for ecosystem-based fishery management

Under the EU biodiversity strategy, changes in fishery management are expected to move fishing activity in Europe towards an ecosystem-based approach by 2030 and to achieve this goal it is essential to identify the spatial distribution of the most valuable commercial fisheries. Using geo-referenced census data of Nephrops norvegicus burrows from underwater TV surveys, the spatio-temporal distribution patterns on the Aran grounds (west of Ireland) from 2002 to 2018 was investigated in relation to habitat and fishing exploitation. A geostatistical approach revealed a patchy distribution, varying in size and intensity over the years. The mud content of the seabed was not influential in explaining spatial variability of burrow distribution. Spatio-temporal analysis showed an overall depletion of burrow abundance over the central area of the study contrasting with its margins and leading to an increase in vessel search activity towards the periphery. This study of the Aran ground stock revealed a decreasing trend in N. norvegicus density from 2002 to 2018, despite increasing landings. It also highlighted spatially variable adverse effects of fishing pressure across different areas. These findings may inform habitat conservation planning in line with EU regulations on fishing impacts.