Encouraging encounters: unusual aggregations of bowhead whales Balaena mysticetus in the western Fram Strait

• Main Authors: de Boer, MN, Janinhoff, N, Nijs, G, Verdaat, H
• Format: Article
• Language: English
• Published: Inter-Research 2019-06-01
• Series: Endangered Species Research
• Online Access: https://www.int-res.com/abstracts/esr/v39/p51-62/

The subpopulation of the bowhead whale Balaena mysticetus in the East Greenland-Svalbard-Barents Sea is endangered and until recently was believed to number in the tens. Recent studies have suggested that this subpopulation appears to be increasing. Here, we report on unusual aggregations of bowhead whales within the Fram Strait. We present opportunistic and effort-corrected observations of bowhead whales made from a small expedition vessel during cruises in June (2015-2018). Bowhead whales were sighted on 85 occasions (220-227 whales). An aggregation in 2015 (n = 84 whales) and high numbers in 2018 (n = 104-110) exceeded all previous records. The index of whale abundance was significantly higher in open water-leads (1.08-1.14 whales km-1 of survey effort) compared to areas with drift-ice (0.51-0.53 whales km-1). The highest abundance index was measured in deep waters where the bottom slope was relatively steep. Our findings highlight the temporal and spatial consistency of this species in areas with relatively loose ice cover (open water-leads) and steep slopes. It is unknown how global warming and resultant changes in ice-extent are going to affect bowhead whales within the Strait and whether they will find new feeding grounds due to an expanding open-ocean habitat. These slopes may become increasingly important to bowhead whales and Arctic top predators as a spring/early summer feeding ground. These relatively large numbers of bowhead whales are encouraging and can help direct future research monitoring programs to study the population ecology of these endangered whales.