An extremely rare stranding in the St. Lawrence

CWHC-Québec and QMMERN necropsy team members (from left to right): Justin Farault, Viviane Casaubon, Shannon Ferrell, Amélia Dalpé and Méduline Chailloux (QMMERN)
A team from RCSF-Québec and the Quebec Marine Mammal Emergency Response Network (QMMERN) carried out the postmortem examination of a northern bottlenose whale (Hyperoodon ampullatus) found dead on the shores of Île d’Orléans (Quebec) at the end of October. This adult female, which weighed nearly 2,500 kg and measured 6.3 meters in length, appeared to be in good nutritional condition. Although the cause of stranding could not be determined based on the postmortem examination, we believe that infectious and traumatic (such as a collision with a boat) causes of death can be eliminated, even though the decomposition state of the carcass may have masked certain pathological changes. Altogether, the presence of a large quantity of squid beaks in the stomach of this whale (suggestive of death from an acute event as the whale was recently feeding), the absence of an obvious pathological condition and the location of this stranding raise the possibility of an accidental stranding. Different factors have been proposed to explain this type of “accident” which is often suspected in apparently healthy beaked whales before stranding (McAlpine et al 2023). First, beaked whales are known to be particularly sensitive to noise pollution, a well-known disturbance within the St. Lawrence waterway. It is proposed that this noise pollution may interfere with the echolocation and communications capabilities of whales, thereby affecting their foraging behavior and spatial orientation (McAlpine et al 2023). In addition, the fluvial environment is variable in depth, salinity and turbidity, which generates a potential for reverberation artifacts and acoustic disorder which further complicate spatial orientation based on echolocation in this species not accustomed to navigating in shallow waters. Indeed, this species of the Ziphiidae family usually navigates in the deep waters (more than 500 meters) of the North Atlantic and is therefore probably poorly suited to navigation in coastal areas.

Every organ is evaluated thorough the necropsy, starting with the skin and blubber to access the internal organs.
The presence of this species in this zone of the St. Lawrence is very unusual; the last documented visit to this region was more than 30 years ago when an adult female and a juvenile stranded within a few days of each other. The fact that this whale had been recently feeding before its stranding suggests that it followed its prey upstream of the St. Lawrence River. We can only wonder whether the modification of the geographic distribution of several marine species caused by climate change will increase the frequency of exploration of unusual regions by certain species of marine mammals in search of food resources. If this is the case, this could increase the risks of accidental strandings as well as the problems associated with increased exposure to human activity.
Despite legal protection for decades, the Scotian Shelf population of northern bottlenose whales is still classified as endangered (COSEWIC 2002). As sightings of live specimens are rare, necropsies of stranded individuals constitute the most important source of information for this species. These examinations allow us to learn more about the biology and causes of mortality of this species for which knowledge remains limited.
For more information on this stranding, visit the following page: https://baleinesendirect.org/en/une-baleine-a-bec-echouee-sur-lile-dorleans/
References :
- Fisheries and Oceans Canada. 2017. Action Plan for the Northern Bottlenose Whale (Hyperoodon ampullatus), Scotian Shelf population, in Atlantic Canadian waters. Species at Risk Act Action Plan Series. Fisheries and Oceans Canada, Ottawa. iv + 37 pp.
- McAlpine, D.F., Wimmer, T., Ledwell, W., Daoust, P.Y., Bourque, L., Lawson, J., Bachara, W., Lucas, Z., Reid, A., Lair, S., François, A., Michaud, R. (2024). A review of beaked whale (Ziphiidae) stranding incidents from the inshore waters of eastern Canada. The Canadian Field-Naturalist, 137(3), 201-231.
- Whitehead, H., Faucher, A., Gowans, S., & McCarrey, S. (1996). COSEWIC Assessment and Update Status Report: On the Northern Bottlenose Whale, Hyperodon Ampullatus, Scotian Shelf Population, in Canada. Committee on the Status of Endangered Wildlife in Canada.