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Topic

Using Acoustics to Explore Fin Whale (Balaenoptera physalus velifera) Ecology and Habitat in British Columbia

Department of Geography

Date & location

• Tuesday, November 12, 2024

• 2:00 P.M.

• David Thompson Building, Room B215

• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Dave Duffus, Department of Geography, University of Victoria (Co-Supervisor)

• Dr. Rianna Burnham, Department of Geography, UVic (Co-Supervisor)

• Dr. Svein Vagle, Department of Geography, UVic (Member)

• Dr. Thomas Doniol-Valcroze, Fisheries & Oceans Canada (Outside Member) 

External Examiner

• Dr. Catherine Berchok, Alaska Fisheries Science Centre, NOAA 

Chair of Oral Examination

• Dr. Min Tsao, Department of Mathematics and Statistics, UVic

   

Abstract

Globally, fin whales (Balaenoptera physalus) were heavily targeted by commercial whaling. Despite this, some populations are recovering; their numbers are increasing in the Southern Hemisphere and North Atlantic. Fin whales are listed as vulnerable on the International Union for Conservation of Nature (IUCN), although populations worldwide show varying degrees of recovery. 

Fin whales were once the most abundant large cetacean species off the coast of British Columbia (BC). They are currently listed under Canada’s Species at Risk Act (SARA) as Threatened, although their status is currently in consideration for downlisting following recommendations by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2019. Although fin whales may be returning to coastal areas in BC, efforts to track their recovery in their core habitat, in deeper waters and off the shelf break, has been limited. Much of what is known about their habitat use, ecology and seasonal movements come from details from historical catch records, with recent designated studies looking to refine this knowledge. 

In this thesis, I consider the potential recovery of fin whales and use acoustic recordings from two study sites in BC waters to analyze their vocalizations. If populations are recovering in BC, recording and analyzing their acoustic behaviour as they rebuild their social and physical connectivity can provide clues to how they are responding after decades of removals. 

Primarily driven by the considerable number of fin whale vocalizations observed in the acoustic recordings, I create a comparative analysis of fin whale call types to provide finer resolution to the spatial and temporal distributions of vocalizations. The presence of 20 Hz and 40 Hz call types, associated with breeding and foraging behaviour, respectively, were analyzed to determine fin whale habitat use. This comparison analysis indicated fin whales use coastal and offshore areas very differently; considerably higher call presence of both types was observed offshore, and song patterning was only present here. 

The diverse range of call parameters observed within the 40 Hz call type, particularly from the offshore study location, led to further analysis for the potential for sub-division within this call type. Cluster analysis indicates the structure of 40 Hz call types is more varied than previously recognized and determines five subcategories within the 40 Hz type based on call features. I further explore the potential of subcategories within this call type by analyzing the relative presence of fin whale 40 Hz calls over daily, monthly and seasonal time periods to better understand drivers of the variability. 

Fin whale song patterns in the offshore acoustic recordings at Clayoquot Slope suggest BC waters are used for courtship, breeding and calving. The difference in song structures may suggest at least two populations using these waters. Although the dominant song pattern structure matched previous findings for the west coast of North America, considerable change in pattern timing was evident. Additionally, new song patterns not previously described for this region were found. 

Overall, knowledge on whale acoustic use and the value of acoustics to their ecology is still over-simplified, but our understanding increases as elements of their use of acoustics is more deeply studied. Some of my observations and understanding of various fin whale acoustic signals have yet to be described in the current literature. Fin whales have a more complicated acoustic repertoire than previously thought and the variety of calls observed indicates BC is an important habitat for recovering populations.