Wandering whales? Relationship between whales and the sea ice environment in the Southern Ocean

Each austral summer large baleen whales migrate into the Southern Ocean to feed on krill. The melting of sea ice leads to algal blooms which allow rapid growth and development of krill. In order to predict how baleen whales will respond to long-term changes in the physical environment, we need to understand the relationships between baleen whales, their prey and the physical environment. The spatial models in this thesis are based on visual observations by whale observers onboard ships in open waters. The model analyses suggest that Antarctic minke whales are more often found close to the sea ice edge, continental shelf and frontal systems. Estimates show higher numbers of minke whales in regions that experienced more sea ice melting during austral spring and summer. These findings strongly suggest that the amount of sea ice cover, and especially its seasonal change, affects populations of minke whales at the regional scale. For the Scotia Sea, different species of baleen whales may target different types of krill. Minke whales and humpback whales were more often found in waters inhabited by juvenile krill, while fin whales were more often found in deeper waters, inhabited by adult krill. Improved understanding of whale behaviour will help us to better predict how baleen whales will respond to environmental change. We hardly know how far away baleen whales can detect krill swarms and how they forage in a three-dimensional environment. Recent advances in infrared detection and acoustic research are promising techniques to remedy this knowledge gap.