Summary
A popular hypothesis established in the 1980s proposed that the decline in whale populations in the Southern Ocean due to exploitation in the early to middle 20th century resulted in a ‘krill surplus’. It was proposed that other krill predators were released from a food-limited state, allowing populations to increase and the composition of the predator community to change. In particular, populations of crabeater seals (which consume krill, not crabs) were predicted to increase by a factor of 10 over the 50 years from the middle to the end of the 20th century. However, evidence in support of this hypothesis was sparse and the predictions highly speculative. Surveys of crabeater seal abundance off east Antarctica in the early 1970s, and similar recent surveys in the same region in the summer of 1999/00, have allowed earlier predictions of large population increases to be examined with empirical data. At both points in time visual surveys of seals hauled out on the ice were undertaken from ships and aircraft throughout the sea-ice between 70-150ºE, and counts were corrected for the proportion of seals in the water. There was no evidence for change of the magnitude predicted having occurred in this region. The ‘krill surplus’ hypothesis, and the evidence originally considered to support it, are re-examined in the light of these findings.