The marine ecosystem off Sermilik, East Greenland, is a high productivity marine ecosystem, but the rapid sea temperature fluctuations in the area result in large variations in species composition and relative abundance of these between years. Such changes are especially visible in the distribution of the economically important pelagic fish stocks. However, another factor that also affects the abundance and distribution of these commercially important fish species are the apex predators that target them in large numbers during the short arctic summer.
One of them, the North Atlantic humpback whale (Megaptera novaeangliae), migrates seasonally to Greenlandic waters to forage during summer, where they feed on large zooplankton and pelagic schooling fish. Thus, an increase in abundance of humpback whales, together with other species of arctic baleen whales, therefore, likely play an increasingly important role in top-down regulation of pelagic fish stocks. This in concert with climate changes add to the complexity of forecasting the sizes of fish stocks and hence also to establish catch quotas on an informed basis.
Humpback whales are known to be opportunistic feeders and are accordingly well equipped to target areas where prey species composition and densities fluctuates. However, the quantity and species composition of their prey are unknown on the Greenlandic east coast, and their direct or indirect effects on commercially interesting fish stocks are therefore currently completely unknown.
In this PhD project, I wish to quantify the biomass turnover by the fast-growing population of humpback whales feeding on commercially important fish stocks in East Greenlandic waters. I will uncover what prey species they target and relate such food preferences to the abundance and energy requirements of the humpback whale population to assess their top down effects on a highly important arctic marine ecosystem that faces rapid changes due to increasing sea temperatures.