Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Scales of distribution and biomass of Antarctic krill (Euphausia superba) in East Antarctica (#81)

Martin J Cox 1 2 , Gavin Macaulay 2 3 , Madeleine J Brasier 4 , Alicia Burns 5 6 , Olivia J Johnson 4 , Robert King 1 2 , Dale Maschette 1 2 , Jessica Melvin 2 4 , Abigail Smith 1 2 , Christine K. Weldrick 2 , Simon Wotherspoon 1 , So Kawaguchi 1 2
  1. Australian Antarctic Division, Kingston, TAS, Australia
  2. Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas, Australia
  3. Aqualyd Limited, Wakefield, New Zealand
  4. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  5. School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
  6. Taronga Institute of Science and Learning, Taronga Conservation Society Australia, Mosman, NSW, Aus

Regular independent monitoring is an important component of the successful management of pelagic animals of interest to commercial fisheries. For Antarctic krill (Euphausia superba), monitoring is typically carried out by ship-based acoustic-trawl surveys that are used to estimate biomass. In turn, biomass estimates and associated stock assessments may be used to set catch limits for commercial fisheries.   However, ship-based surveys are time consuming, costly, and the remoteness of the East Antarctic leads to logistical challenges, which unfortunately leads to infrequent surveys of krill biomass.  Using the results of a 2021 large-scale krill survey (longitude range 55°E to 80°E; survey area = 775,732 km2), we examine two alternative survey methods that may help provide more frequent monitoring opportunities. Firstly, using the results of a smaller survey (area = 4,902 km2) conducted during the large-scale survey, we examine how representative krill densities from the small-scale survey were over a latitudinal range by comparing krill densities from the large-scale survey split into latitudinal bands.  Secondly, we use acoustic-optical data from a lander deployed during the large-scale survey to develop a seasonal picture of the vertical distribution of krill.