CEPHALOPOD PREY OF THE BLACK-BROWED ALBATROSS DIOMEDEA-MELANOPHRYS ATSOUTH-GEORGIA

Regurgitations were collected from 41 black-browed albatross adults fe eding chicks at Bird Island (54-degrees-S 38-degrees-W), South Georgia in February 1986. The samples were sorted into recognisable food cate gories and weighed. Cephalopods were identified by means of the lower beak, or in some cases the gladius, and allometric equations were used to calculate mantle length and wet body weight represented by beaks. The samples contained 35.5 % Euphausia superba, 30.9 % cephalopods and 27.1 % fish, by weight. A total of 21 samples contained recognisable cephalopod remains and 20 contained specimens that could be identified . In all, 50 cephalopod specimens, representing an estimated 6,866 g w et weight, were identified. The diet was dominated in terms of numbers , weight and percent occurrence by the ommastrephid squid Martialia hy adesi, and in most cases the entire squid was present with only partia l digestion of the skin and arm armature. The cranchiid squid Galiteut his glacialis was the only other cephalopod of numerical importance bu t no soft parts were present suggesting that, although significant in the diet of the adults, this species was not being fed to chicks. One specimen each of Gonatus antarcticus, Chiroteuthis sp., Histioteuthis sp. B. and the octopodid Pareledone polymorpha were also present. The cephalopod composition of the diet corresponded closely with a collect ion made 10 years earlier. The commonest species in the bird's diet, M . hyadesi, has not been found in net and jig samples at South Georgia although it has been taken from the Antarctic Polar Frontal Zone to th e west of the Island. The presence of almost complete, undigested, spe cimens of M. hyadesi in the bird's diet indicates that it occurs relat ively close to South Georgia. M. hyadesi preys largely on myctophid fi shes, which themselves prey on small zooplankters, so a significant co mponent of the black-browed albatross diet depends on a food chain whi ch largely by-passes E. superba.