Is it ‘boom times’ for baleen whales in the Pacific Arctic region?

Abstract

The marine ecosystem in the Pacific Arctic region has experienced dramatic transformation, most obvious by the loss of sea ice volume (75%), latesummer areal extent (50%) and change in phenology (four to six weeks longer open-water period). This alteration has resulted in an opening of habitat for subarctic species of baleen whales, many of which are recovering in number from severe depletions from commercial whaling in the nineteenth and twentieth centuries. Specifically, humpback, fin and minke whales (Megaptera novaeangliae, Balaenoptera physalus and Balaenoptera acutorostrata) are now regularly reported during summer and autumn in the southern Chukchi Sea. These predators of zooplankton and forage fishes join the seasonally resident grey whale (Eschrichtius robustus) and the arctic-endemic bowhead whale (Balaena mysticetus) in the expanding open-ocean habitat of the Pacific Arctic. Questions arising include: (i) what changes in whale-prey production and delivery mechanisms have accompanied the loss of sea ice, and (ii) how are these five baleen whale species partitioning the expanding ice-free habitat? While there has been no programme of research specifically focused on these questions, an examination of seasonal occurrence, foraging plasticity and (for bowhead whales) body condition suggests that the current state of Pacific Arctic marine ecosystem may be 'boom times' for baleen whales. These favourable conditions may be moderated, however, by future shifts in ecosystem structure and/or negative impacts to cetaceans related to increased commercial activities in the region.

Historical and potential future importance of large whales as food for polar bears

“…). Although carrion from large whales may have facilitated polar bear survival through past ice‐free periods, and large whale populations are slowly increasing throughout much of the Arctic (Moore ), the current reliability of this food source is less certain. Recovery of previously overharvested populations of large whales varies across the Arctic.…”

Strong and lasting impacts of past global warming on baleen whale and prey abundance

“…Recent predictions of the effects of the current global warming on marine mammal populations have relied upon field observations (28,29). Baleen whale species, such as humpback, fin (B. physalus) and blue whales, appear to arrive earlier and at higher latitudes on the summer feeding grounds, increasing competition with polar species, such as the bowhead whale (Balaena mysticetus) (30). However, although some baleen whale species appear to benefit from global warming at present, the findings reported here suggest that the oceanographic and ecological changes introduced by global warming initiated geological and biological processes with longlasting and wide-ranging impacts on the marine ecosystem.…”

Late summer distribution and abundance of ice-associated whales in the Norwegian High Arctic

“…in contrast to the 15 sightings involving 27 individuals in this survey. This suggests that animals might have migrated into this area from other places over the past decade (Boertmann et al 2015), facilitated by the reduction in sea ice (see Heide-Jørgensen et al 2007) and increasing trends in some populations (Moore 2016), or alternatively, and most likely, this suggests a patchy, variable distribution of the animals in this stock. But, further studies are needed to confirm the degree of inter-and intra-annual variability in distribution.…”