Observations of southern right whales (Eubalaena australis) surface feeding on krill in austral winter at South Georgia

Southern right whales (Eubalaena australis) occur in the waters around the sub-Antarctic island of South Georgia, where they use the area to feed during the austral summer months (Jackson et al., 2020; Kennedy et al., 2020; Moore et al., 1999; Richardson et al., 2012). Although Antarctic krill (Euphausia superba) is known to be an important part of their diet, there have been few descriptions of southern right whale foraging behavior or prey (Argüelles et al., 2016; Hamner et al., 1988; Hoffmeyer et al., 2010; Jackson et al., 2020; Reid et al., 2000; Seyboth et al., 2016; Valenzuela et al., 2018). Southern right whales in the South Atlantic are generally found at lower latitudes over the austral winter on calving grounds, including off Brazil and Argentina (Crespo et al., 2019; Groch et al., 2005). However, here we document observations of southern right whales feeding at South Georgia during austral winter, in July 2022. Whales were observed surface feeding on krill just after sunset on three occasions and, based on these observations, on a fourth occasion at sunset, observers judged that the whales were about to start feeding.

Observations were made from the M/V Pharos SG as part of ecosystem research into the South Georgia winter krill fishery (Winter Krill Project; https://www.bas.ac.uk/project/winter-krill-at-south-georgia). Line transect surveys were conducted off the north coast of South Georgia during the austral winter of 2022, with research activities including predator observations, active acoustics, and both scheduled and opportunistic plankton trawls.