Threat assessment for northern Bottlenose whales (Hyperoodon ampullatus) off eastern Canada, with a focus on the Scotian Shelf population

This document provides an updated description of potential and known threats to Northern Bottlenose Whales (NBW, Hyperoodon ampullatus) off eastern Canada. There are two NBW populations that are recognized in Canada and managed separately: the Scotian Shelf (SS) population, which are listed as Endangered under the Species at Risk Act (SARA) and the Davis Strait-Baffin Bay-Labrador Sea (DSBBLS) population, which have not been listed under the SARA. The threat assessment considered 15 categories of threats to NBW, and risk was evaluated at two nested geographic scales: (1) for the Endangered Scotian Shelf population (SSDU), and (2) for both populations of NBW (SSDU and DSBBLS) in the western North Atlantic (NWA). Individual-level and population-level impacts of threats were assessed using best available information on impacts to NBW, beaked whale species and cetaceans, identifying uncertainty levels given sources ranging from published literature to expert review. The individual level of impact for both the SSDU and NWA was assessed as high or extreme for historical whaling, military sonar, entanglement, risks of depredation, vessel strike, and oil spills. For the SSDU, the population level of impact was assessed as either high or extreme for climate change, historical whaling, military sonar, entanglement, vessel strikes, and oil spills. For the NWA, the population level of impact was assessed as high for historical whaling, medium for climate change, and low for vessel noise, while the other 12 threats were assessed as unknown, primarily because there is no information on the size of the DSBBLS population. Categorization of a particular threat as unknown at the individual or population level of impact does not indicate a lack of effect or that the threat is not important. In many cases impacts are known to occur on individuals even if population-level impacts have not been or cannot be easily measured. It is likely that mortalities, injuries, and other impacts are underreported due to the offshore habitat of NBW. This threat assessment does not take into account direct impacts on NBW habitat, indirect effects or limiting factors (e.g., small population size, low genetic diversity), interactions between multiple threats, or cumulative impacts. Cumulative effects may alter the level of risk represented by individual threats. Predicted effects of climate change are particularly concerning, as they are likely to interact with other threats and despite uncertainties, may have a high level of impact on NBW.

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