Why is it important to understand the foraging habits of Arctic whales?

In the ocean, natural and human-driven factors may drive shifts in ecosystems. Such changes, whether sudden or gradual, can affect the food web by causing a redistribution of prey that seasonal predators, such as migrating whales, depend on. Prey redistribution of this type may not only cause predators to change their migration routes and timing, but also to adapt their foraging habits.

An international team of researchers from Norway, the United Kingdom and the United States studied the foraging habits of humpback whales (Megaptera novaeangliae) in the Barents Sea, north of northern Norway. These whales typically spend the summer and fall foraging in the Barents Sea and Norwegian Sea before migrating to the West Indies and Cape Verde Islands to mate and reproduce during the spring months.

The team’s work, titled It’s Okay If You Do: Arctic Humpback Whales Respond to Pre-Migratory Winter Foraging Opportunities, was published in Royal Society Open Science.

According to current research, large numbers of humpback whales have not been observed in the northeastern Atlantic Ocean since the time of commercial whaling in the area between 1881 and 1904, when forage fish were known to be plentiful there.

However, during this study, researchers documented individual whales – first seen and identified during the summer in the Barents Sea – spending the winter in northern Norway, searching for spring-spawning Norwegian herring (Clupea harengus). These herring are also known to have started overwintering in the area – along the whales’ migration route – in large numbers since 2010.

The team collected biopsy and photographic evidence of humpback whales in the Barents Sea near the Svalbard archipelago and in several fjords in northern Norway at various points between 2010 and 2019. Due to the warm waters of the North Atlantic Ocean, northern Norway is empty. of sea ice in winter, and between June and December, the waters of the Svalbard archipelago are also ice-free.

Seasonal data matches of whale observations made in the Barents Sea and northern Norway showed that during their migration, some whales continued to forage in the northern Norwegian fjords.

Researchers documented an increased number of females during their winter observations in northern Norway, and estimated that the pregnancy rate in winter there was higher than it was earlier in the season. From this they concluded that pregnant females – whose gestation period lasts between 10 and 13 months – may be particularly vulnerable to continuing the foraging season in northern Norway, in order to maximize their energy.

In addition, the study indicates that whales began feeding in the fjord area north of Norway in 2010, coinciding with significant concentrations of herring there. According to a study conducted in 2017 in Mammalian biologyHumpback whales had not been present in the area before then, as these herring stocks overwintered in the fjords to the south.

Why is this important? The current study notes that “winter foraging on herring found in a fjord is a strategy preferentially used by female humpback whales in northern Norway. Our findings suggest that this strategy has become an important annual event for humpback whales, conditional on their “Herring winters in these areas.” “straits.”

More broadly, it will be important for future studies to examine and evaluate the impact of human-driven factors on migratory species, especially in their critical feeding areas. Despite the International Whaling Commission’s commercial whaling ban since 1985, M. novaeangliae remains threatened with extinction in some areas, including Cape Verde. The researchers stress that ecosystem management should specifically prioritize shipping and fishing activity.