Unclassified - Non-Classifié Dear MARMAMers,
My co-authors and I are pleased to share a new research document focused on the seasonal distribution and density of whales and porpoises in the coastal waters of southern British Columbia: McMillan, C.J., Keppel, E.A., Spaven, L.D., and Doniol-Valcroze, T. 2026. Seasonal Spatial Densities of Cetaceans in the Southern Salish Sea and on Swiftsure Bank. DFO Can. Sci. Advis. Sec. Res. Doc. 2026/059. x + 70 p. This paper is available at the following link: Research Document 2026/059<https://csas-scas.dfo-mpo.gc.ca/publications-publications/bfff1f10-9e73-4368-ac8b-18695816fb4d?lang=en> Abstract: Effective assessment and management of anthropogenic threats to marine mammals requires knowledge of the distribution and habitat use of affected species and how their density patterns vary over time. Knowledge of seasonal density and distribution of cetaceans was identified as a data gap by the Canada Energy Regulator, in relation to the need to mitigate impacts of increased shipping traffic associated with the Trans Mountain Expansion Project (TMX). In response, Fisheries and Oceans Canada conducted a series of 29 systematic, multi-species boat-based cetacean surveys across all seasons from August 2020 to August 2024, covering the southern Salish Sea and Swiftsure Bank. Eight species of cetaceans, including six populations listed under the Species At Risk Act, were detected. Distance sampling methods and density surface modelling were used to provide the first year-round, spatially explicit density estimates for humpback whales, harbour porpoises, and Dall's porpoises in the southern Salish Sea and on Swiftsure Bank. All three species showed strong spatial and seasonal density patterns. Areas of highest density for humpback whales included Swiftsure Bank in all seasons, and central and western Juan de Fuca Strait in summer and fall. High densities of harbour porpoises occurred in Haro Strait, Boundary Pass, and eastern Juan de Fuca Strait year-round, while Dall's porpoise density was highest in the southern Strait of Georgia in fall and winter, and in the western portion of the study area in spring and summer. These results will be used to inform future risk assessment models and underscore the need for management strategies that are aligned with seasonal density patterns rather than relying on data from a single season or year. Thank you, Christie __________________________________________________________________ Christie McMillan (she/her) Cetacean Research Program Fisheries and Oceans Canada Pacific Biological Station 3190 Hammond Bay Rd, Nanaimo, BC, V9T 6N7 236-330-1435
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