Revised estimates of seabed areas within the 500 m isobath of the South Orkney Islands (Subarea 48.2) and consequences for standing stock biomass estimates of nine species of finfish

A revised bathymetric map of the South Orkney Islands (Subarea 48.2) was generated using several integrated bathymetric databases and newly available acoustic seafloor data. The region extends from 60.2ºS-62.2ºS latitude and 42.5º-47.5º longitude. From the integrated data sets, areas of seabed within the 500 m isobath were computed for 50 m depth intervals. Areas were calculated based on interpolated surface area of seabed incorporating seafloor slope. These results were compared to the previously reported estimates of Everson (1997) for the 50-150, 150-250, and 250 to 500 m depth intervals. The updated estimates are about 1,424 (20%) nautical miles larger in area within the 50-500 m isobaths than Everson’s estimates, though changes in area are specific to the depth interval. There is a corresponding change in estimated biomass within strata when these areas are incorporated into swept area trawl survey models, though not for total estimated biomass. Of the nine species examined, the point estimate of total biomass increased from 5%-30% for eight species and decreased 20% for one.