Summary of monitoring and research effort and preliminary results from the 2019 Scotia Sea krill monitoring survey with FV Cabo de Hornos

We here summarise the sampling effort and some preliminary findings from the 2019 Scotia Sea krill monitoring survey with the F/V Cabo de Hornos. The vessel was chartered by the Association of Responsible Harvesting Companies (ARK) and manned with personnel from the Institute of Marine Research to carry out a significant part of the 2019 Scotia Sea large scale krill monitoring. All sections of the large scale survey area were visited, and about 80 % of the coverage planned for the vessel was completed, the remaining had to be skipped due to time constraints. Altogether 3928 nautical miles were travelled on transects, and in addition to the acoustic data collection which is presented in a separate manuscript, 68 trawl stations for biological sampling with associated CTD casts were carried out. Marine mammals and birds were monitored continuously during daylight hours, as long as weather permitted. In addition, deployment of four acoustic moorings and 9 replicate measurements on board of krill acoustic sound speed and density contrasts were carried out. Euphausia superba dominated in the trawl samples on the shelf north of the south Shetland islands, in the Bransfield Strait, the shelf north of the South Orkneys and south of South Georgia. Salps, mainly Salpa thompsoni dominated north of the South Shetland shelf, and in the vast oceanic waters between the north and south Scotia ridge. Also amphipods, in particular Themisto gaudichaudii and other krill species dominated in some stations. E. superba length distribution were dominated by two modes, one of very large animals averaging around 55 mm dominating in the South Shetland area, and a second mode between 40 and 50 mm dominant further east, in particular around South Georgia. Small animals were only rarely sampled and almost uniquely on the shelf to the east of the Antarctic Peninsula. Fin whales were the dominating whale species in abundance, followed by humpback whales.