CEPHALOPOD PREDATION BY THE KING PENGUIN APTENODYTES-PATAGONICUS FROMSOUTH GEORGIA

The king penguin Aptenodytes patagonicus is a sub-Antarctic species th at feeds primarily on mesopelagic fish and cephalopods in the vicinity of the Antarctic Polar Front (APF). We examined the cephalopod prey o f adult penguins at a breeding colony on South Georgia during 4 austra l summers, 1990 to 1994. The most important prey (similar to 97 % by m ass) of the king penguins was found, in a related study, to be mesopel agic fish, mainly myctophids. The penguins' cephalopod prey, which con stituted the remaining 3%, was shown in this study to be dominated by the ommastrephid squid Martialia hyadesi, both in terms of numbers and biomass. Other squid species were typical of the South Georgia/Antarc tic Polar Front (APF) area but only relatively small specimens were pr esent and, apart from Gonatus antarcticus, the presence of flesh indic ated that they were probably mostly caught close to the island. M. hya desi generally fell in the same size range as M. hyadesi exploited by commercial fisheries in the South Atlantic. In the 1992/93 summer, whe n krill was abundant at South Georgia, the amount of squid consumed, e specially M. hyadesi, was substantially less than in the other years. This coincided with a reduction in the amount of the myctophid Kreffti chthys anderssoni, which is the major prey of M. hyadesi, in the pengu in diet. The total consumption of cephalopods by the king penguin at S outh Georgia is estimated to be about 75 000 t yr(-1). Of this, some 3 600 to 6000 t yr(-1) is estimated to be M. hyadesi. This might underes timate consumption if the penguins consume a greater proportion of squ id in the winter, as they do in other sectors of the Southern Ocean.