Information on diet composition, foraging effort and breeding success of the Antarctic Shag (Phalacrocorax bransfieldensis) was obtained at three colonies on the Antarctic Peninsula, dur-ing the 1997/98 breeding season. Fish was the most important prey at each of the colonies sampled, followed by octopods and gastropods. Among colonies, there were marked differences in the size of the fish consumed, which was smaller at Py Point. This was mainly due to the larger number of speci-mens of the smallest fish prey species consumed there. Shags from Py Point performed longer forag-ing trips and spent more time per day foraging. Although at the beginning of the study the number of chicks per nest observed at the three colonies was similar, the number surviving to fledge at Py Point was markedly lower. The relative higher foraging effort and lower breeding success observed at Py Point might be related to the differences in the fish consumed between colonies. My results suggest that the decline in the inshore fish populations observed around the South Shetland Islands could be one of the reasons explaining the steady decrease in the number of breeding Antarctic Shags observed at colonies monitored in this archipelago.%通过调查获得了南极半岛3个南极鸬鹚（Phalacrocorax bransfieldensis）群落在1997/98年繁殖期的食物组成、取食投入及繁殖成功率的相关资料。鱼类是这3个鸬鹚群落最主要的食物来源，其次是八足类及腹足类动物。3个群落的鸬鹚所捕食的鱼类大小有显著差异，在Py Point处的最小，这主要是因为在该处获得的小体型的鱼类样本数目最多。Py Point处的鸬鹚取食路径最长，日均取食时间最多。Py Point处的雏鸟存活率最低，尽管在调查初期这3个群落的平均窝雏数几近相同。该处鸬鹚的取食投入最多但繁殖成功率却最低，可能与群落之间捕食的鱼类差异有关。南设得兰岛附近靠近海岸的鱼类种群数量不断下降，或许能解释为何在该列岛繁殖的鸬鹚群数目越来越少。
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