400-Metre Regulatory Distance for Blue Whales Proving Effective

Depending on the feeding ground and the krill species considered by the model, the impact of disturbance on foraging can vary. In comparison, the energy loss associated with three hours of boat presence would be equivalent to a 5% decrease in krill density in blue whale habitat. Such a figure may appear negligible. However, changes in diet are magnified when scientists combine the impact of disturbance with the decreases in krill density that are to be expected with climate change. “The importance of krill for blue whales, as their sole food source, is the reason behind the krill fishing moratorium in Canada since 1998,” points out Marie Guilpin. These discoveries clearly underscore the importance of abiding by the regulations for navigating in the presence of whales. In the St. Lawrence Estuary and the Saguenay Fjord, all watercraft much maintain a distance of 400 metres from any threatened or endangered species, i.e. blue whales, bottlenose whales, North Atlantic right whales and belugas. Elsewhere, such as in the Gulf of St. Lawrence, this distance is 100 metres.

For blue whales, summer means foraging, since once they return to their winter range they do not eat for the remainder of the year. This is why potential declines in the abundance of krill (their only prey) as well as in their feeding ability due to boat traffic are of particular concern.

If blue whales are not getting enough to eat, this could explain why researchers have not observed them in large numbers in recent decades. Indeed, because it is so energy intensive, reproduction can be postponed in animals that are undernourished.

In order to verify whether the blue whales that visit the St. Lawrence can theoretically store enough energy to reproduce, the research team plans to develop a new model that will take into account energy expenditure not only during the foraging season, but also during migration and reproduction.