Temporal variation in the feeding habits of female Southern elephant seals, Mirounga leonina, at Isla 25 de mayo/ King George Island, South Shetland Islands, Antarctica

DANERI G.A.; MARSCHOFF E.; HARRINGTON A.; NEGRETE J.; DESCALZO M.

West Palm Beach, Florida

Congreso; 24th Biennial Conference on the Biology of Marine Mammals; 2022

Society for Marine Mammalogy (SMM)

The Southern elephant seal, Mirounga leonina, is an important apex predator that is widelydistributed in the Southern Ocean, their main breeding concentrations located onsubantarctic Islands. Food availability in the ocean has been suggested as a proximate causein changes in the population numbers of different Southern elephant seal colonies. The aimof this study was to examine the feeding habits of the female component of the Isla 25 demayo/King George Island elephant seals colony, throughout 8 consecutive years (latespring/summer 1995/6 - 2002/3) coinciding with the beginning of the moulting period.Mature female seals (N=99) which had recently arrived ashore were anaesthetised and thensubjected to stomach lavage. The diluted stomach contents were sieved (1.0 mm mesh) andthe different prey taxa sorted. For the total period of study the cephalopod diet wasdominated by the Antarctic glacial squid, Psychroteuthis glacialis, which occurred in almost90% of stomach samples and constituted alone 57% in numbers and 64% in massof cephalopods ingested. Other teuthoid species of relevance were Slozarsykoviacircumantarctica and Alluroteuthis antarcticus in terms of occurrence and numbersand Moroteuthopsis longimana in terms of mass. Fish were mainly represented by themyctophid Gymnoscopelus nicholsi which occurred in over 90% of samples, constitutingalmost 80% in numbers and mass of all identified fish. The nototheniid Pleuragrammaantarctica was second in importance though in much lower proportions. Temporal variationin cephalopod predation by seals showed a uniform dominance of P. glacialis, but with anotable decrease in its contribution to the diet between the 1997/8 and 1999/2000 seasons.This could be related to changes in oceanographic conditions and marine communitiesstructure of the Southern Ocean derived from one of the most severe El Niño SouthernOscillation events in 1997/98.