Ross Seals: Pack Ice and Open Ocean Commuters

Abstract

The relative abundance and ranging behaviour of Ross seals (Ommatophoca rossii. were investigated to determine the way oceanographic conditions affect the rarest true Antarctic species of seal breeding off Dronning Maud Land, Antarctica, with a view to using these as bioindicators of environmental change. Shipboard summer surveys were conducted from the bridge of the ice breakers SA Agulhas II (2015/2016. and RV Polarstern (2018.. Satellite-linked dataloggers were deployed on moulted adults in January 2016 (n = 8 females; n = 3 males. and 2018 (n = 2, one per sex.. Four devices failed prematurely, and two devices lasted for a full year until the next moult. Despite the low survey effort, Ross seals were relatively (compared to all other shipboard surveys around Antarctica. abundant in the pack ice of the eastern Weddell Sea in mid-January 2016, seemingly similar to the situation here in the 1970s. Although adult Ross seals give birth, mate and moult in the pack ice, they foraged in open water far north of the seasonal pack ice after breeding, and again after moulting. During their two annual commutes between the pack ice and the open ocean, their distribution overlaps with that of three other phocids within the pack ice (crabeater, leopard and Weddell seals., and with another (southern elephant seal. in the open ocean. With Ross seals predictably found within the eastern Weddell Sea during relief cruises to service SANAE IV and Neumayer III, the commuting of the Ross seals between pack ice and open ocean makes them ideal candidates to carry satellite-linked dataloggers. Such instruments can sample, amongst others, in situ physical and biological oceanographic characteristics at times when oceanographic recordings by other means are difficult or impossible. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.