The abundance of the Antarctic krill (Euphausia superba) has been declining in the western Antarctic Peninsula (WAP), probably as a consequence of the effects of the considerable increase in the sea surface temperature observed in the region. Thus, the performance (reproduction and survival) of the krill consumers may be compromised. In the present study, we investigated the reproductive success of humpback whales (Megaptera novaeangliae) from Breeding Stock G in relation to krill density. The result we found suggests that the warming off the WAP and the expected future increase in the frequency of extreme El Niño events may compromise humpback whale’s rate of recovery in the Southern Hemisphere if such changes negatively affect the production of krill. Therefore, it is recommended that management strategies for krill fisheries consider the effect of climate on the whole Antarctic ecosystem and the potential effect of krill removal on the population recovery of whales.