Insights into cetacean habitat use in British Columbia using visual and acoustic methods
Date
2024
Authors
DeMeyer, Roanan
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Abstract
Cetaceans play critical roles in marine ecosystems as top predators and ecosystem engineers. In British Columbia (BC), cetacean populations are recovering from industrial whaling and responding to other anthropogenic pressures, such as vessel noise, climate change, and ship strikes. Protecting these populations requires knowledge of their habitat use patterns to inform effective management. In this thesis, I use visual and acoustic methods to contribute to the historical and current knowledge of cetacean habitat use in BC’s waters. In Chapter 2, I use visual data gathered via transect line surveys offshore of Clayoquot Sound, BC, between 1993 and 2007. These surveys yielded observations of eleven cetacean species. Analyses of habitat variables indicated significant interspecific differences in habitat use, a negative correlation between Dall’s porpoise group size and sea-surface temperature, and an increased offshore distance for the southward gray whale migration. Interannual changes in sighting rates reflected known population dynamics, while seasonal changes supported inshore-offshore movement patterns for Dall’s porpoise and Pacific white-sided dolphins. In Chapter 3, I use acoustic data gathered from two hydrophones deployed on the east and west coasts of Haida Gwaii in Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve, and Haida Heritage Site from August 2018 to August 2019. Manual analyses of these data were used to identify cetacean call and vessel presence. At least eight species were identified and foraging, breeding, and migratory habitat uses were inferred from call timing and behavioural associations of call types. The maximum frequencies of the loudest identified vessel noise were measured and overlap with cetacean call frequencies, as well as the co-occurrence of cetacean calls and vessels, suggest the potential for call masking and disturbance. Large and small vessels were more common on the west and east coasts, respectively, and these findings inform site-specific noise management recommendations. In Chapter 4, I use these acoustic data to provide insights into the gray whale migration route and habitat use, since these are poorly understood in northern BC. Gray whales were only detected during the northward migration on the east coast, suggesting that the migrations primarily occurred outside the hydrophone detection ranges. The visual and acoustic monitoring conducted in this thesis contributes to cetacean conservation by advancing our understanding of cetacean habitat use and vessel presence in BC.
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Keywords
bioacoustics, cetology, cetacean ecology, biogeography, cetacean management, whales, passive acoustic monitoring, cetacean habitat use, marine protected areas