Whales in the North Atlantic are adapting their feeding habits to share limited food resources as climate change and human activities reshape marine ecosystems, a new long-term study has found.
Researchers analysing nearly three decades of data from the Gulf of St Lawrence discovered that fin, humpback and minke whales are eating more fish and less krill than in the past. The shift is likely driven by growing competition for prey as warming waters reduce the availability of Arctic krill, a key food source.
The study, published in Frontiers in Marine Science, used skin samples collected from more than 1,100 whales between 1992 and 2019. Stable isotope analysis revealed dietary changes across three distinct environmental periods, from cooler conditions in the 1990s to warmer waters and reduced sea ice in recent years.
Lead author Charlotte Tessier-Larivière of Canada’s Maurice Lamontagne Institute said the increasing resource partitioning among the three species suggests heightened competition in response to limited prey. Fin whales, which fed mainly on krill in the 1990s, switched increasingly to fish such as capelin and herring in the 2000s, and later to sand lance and northern krill. Humpback whales relied consistently on a few fish species, while minke whales ate mostly pelagic fish but continued to consume krill later in the period.
Despite the pressures, researchers found no evidence of one species displacing another. Instead, the whales appear to be reducing competition by narrowing their dietary niches. The Gulf of St Lawrence, a major seasonal feeding ground, has experienced rapid environmental change from rising ocean temperatures, shrinking sea ice and increased shipping and fishing. Scientists say the study offers rare insight into how large marine animals respond to long-term ecosystem shifts.
