As the temperatures of the Gulf of St. Lawrence rise, recent Canadian research indicates that the dietary preferences of certain baleen whales are changing due to alterations in available food sources.
Lead researcher Charlotte Tessier-Larivière from Université du Québec à Rimouski highlighted a decrease in Arctic krill, which used to be a significant prey for fin whales in the 1990s. The study suggests that fin and minke whales have transitioned to consuming more forage fish like capelin, mackerel, and herring, which are the primary diet of humpback whales in the region.
Tessier-Larivière emphasized that whale species have demonstrated the ability to adapt their diets based on the availability of preferred prey. However, the full extent of their adaptive capacity remains uncertain.
The shift in whale diets raises concerns about potential competition for food resources and the consequences if prey species experience declines.
Hanna Vatcher, a campaigner at Oceana, expressed both optimism and concern regarding the study’s findings. She noted that the observed changes in whale behavior reflect the broader impact of climate change on marine ecosystems, affecting various oceanic species from large whales to small forage fish.
The research involved analyzing tissue samples from different whale species and their prey over 28 years during summer months. Carbon and nitrogen isotopes in the samples provided insights into the whales’ diet compositions.
In recent years, an increase in forage fish signatures was detected in the tissues of all three whale species, underscoring the significance of these fish in the local food chain.
Despite similarities in their diets, the study revealed signs of “resource partitioning” among fin, minke, and humpback whales, indicating a reduction in food overlap. This suggests that the whales may be targeting different fish species, potentially at varying times or locations to avoid direct competition.
Janie Wray, CEO of BC Whales and North Coast Cetacean Society, highlighted the intelligence of whales in adapting to changing conditions, such as developing new hunting techniques. Collaborative behaviors, like bubble net feeding observed in humpback whales, demonstrate their strategic approach to hunting prey.
Wray emphasized the importance of studying whale behaviors to identify critical marine areas that require protection. By understanding the habits of whales, conservation efforts can focus on safeguarding vital habitats that support these marine mammals.
While the St. Lawrence whale study area is not within a marine protected zone, there are existing protected areas further downstream in the St. Lawrence River. Plans are underway to expand these protected zones to conserve more marine habitats.
Vatcher stressed the need for dynamic conservation strategies that consider climate-informed adaptive management to protect whales and their habitats effectively. By incorporating predictive models and climate projections, efforts can adapt to the changing behaviors of whales and ensure long-term marine conservation.