Science, Faculty of
Zoology, Department of
DSpace
UBCV
Scarff, Taryn M.
Master of Science - MSc
University of British Columbia
Killer whales (Orcinus orca) play an important role in the coastal ecosystems of British Columbia. In recent decades, west coast transient and southern resident killer whales (two of the main ecotypes of killer whales in BC) have changed their use of coastal BC waters. However, seasonal abundance and distribution changes, and reasons for why the changes occurred remain relatively unknown. I used sighting reports of transient and southern resident killer whales from 2016-2023 in the inside waters of Vancouver Island (the Salish Sea and North Island Waters) to evaluate how these ecotypes use the area, and the relative importance of the area to their populations. I determined the proportion of the BC west coast transient killer whale population that use the inside waters and compared these results with southern resident killer whale seasonal variation in occupancy to analyze the difference in use of the Salish Sea between the two ecotypes. I found that approximately 70% of the BC west coast transient population uses the inside waters annually. Transient killer whales were present in the inside waters year-round, with seasonal highs from March-September each year, which corresponded with the presence of prey species that are drawn to the area during times that key fish species spawn. I also discovered an odd vs. even year pattern in transient killer whale presence where transient abundance varies in July of alternating years, which may be related to the return of pink salmon. Southern residents were not observed consistently throughout the year in the Salish Sea and had a fluctuating seasonal presence that peaked in March, July, September and November. These peaks also corresponded with spawning times of key fish species that southern residents rely on for prey. Overall, my results show that the inside waters of Vancouver Island are important for both ecotypes of killer whales, and that their presence in the area relates to spawning seasons of key fish species. These findings contribute to the conservation of west coast transient and southern resident killer whales and highlights the need to maintain the health of the inside waters.
KILLER WHALE USE OF THE INSIDE WATERS OF VANCOUVER ISLAND, BRITISH COLUMBIA by Taryn M. Scarff B.Sc., The University of British Columbia, 2020 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Zoology) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2024 © Taryn M. Scarff, 2024 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the thesis entitled: Killer Whale Use of the Inside Waters of Vancouver Island, British Columbia submitted by Taryn M. Scarff in partial fulfilment of the requirements for the degree of Master of Science in Zoology Examining Committee: Dr. Andrew Trites, Professor, Institute for the Oceans and Fisheries, UBC Supervisor Dr. David Rosen, Assistant Professor, Institute for the Oceans and Fisheries, UBC Supervisory Committee Member Dr. Kaitlyn Gaynor, Assistant Professor, Department of Zoology, UBC Additional Examiner iii Abstract Killer whales (Orcinus orca) play an important role in the coastal ecosystems of British Columbia. In recent decades, west coast transient and southern resident killer whales (two of the main ecotypes of killer whales in BC) have changed their use of coastal BC waters. However, seasonal abundance and distribution changes, and reasons for why the changes occurred remain relatively unknown. I used sighting reports of transient and southern resident killer whales from 2016-2023 in the inside waters of Vancouver Island (the Salish Sea and North Island Waters) to evaluate how these ecotypes use the area, and the relative importance of the area to their populations. I determined the proportion of the BC west coast transient killer whale population that use the inside waters and compared these results with southern resident killer whale seasonal variation in occupancy to analyze the difference in use of the Salish Sea between the two ecotypes. I found that approximately 70% of the BC west coast transient population uses the inside waters annually. Transient killer whales were present in the inside waters year-round, with seasonal highs from March-September each year, which corresponded with the presence of prey species that are drawn to the area during times that key fish species spawn. I also discovered an odd vs. even year pattern in transient killer whale presence where transient abundance varies in July of alternating years, which may be related to the return of pink salmon. Southern residents were not observed consistently throughout the year in the Salish Sea and had a fluctuating seasonal presence that peaked in March, July, September and November. These peaks also corresponded with spawning times of key fish species that southern residents rely on for prey. Overall, my results show that the inside waters of Vancouver Island are important for both ecotypes of killer whales, and that their presence in the area relates to spawning seasons of key fish species. These findings contribute to the conservation of west coast transient and southern resident killer whales and highlights the need to maintain the health of the inside waters. iv Lay Summary I evaluated how transient killer whales and southern resident killer whales use the inside waters of Vancouver Island to find out what months of the year they are present, what area they spend most of their time in, and how many whales from each population use this area. I then compared the similarities and differences in how transients and southern residents use the area. Overall, I found that both types of killer whales spend most of the year in the inside waters, and that the highest number of individuals are consistently present when their prey availability is the highest. I also found that transient killer whales presence in the Salish Sea decreases in July of even years, which may be related to the pink salmon spawning season. These findings show the importance of the inside waters to both populations. v Preface This thesis and the research presented within it is my original work. Under the supervision of Dr. Andrew W. Trites, I developed the research questions and study design, collected the data, conducted the analyses and summarized all my findings in writing. Feedback from my committee member, Dr. David Rosen, was incorporated into the study design and final thesis draft. Suggestions from Dr. John Ford were also included within the initial study design and development of research questions. I collected data from private databases for this project from Jared Towers (Department of Fisheries and Oceans Canada), the Pacific Whale Watch Association and the Pacific Whale Watch Association App, North Island Marine Mammal Stewardship Association, Island Adventures Whale Watching (Erin Gless), and the BC Cetacean Sightings Network (Oceanwise). I also obtained data from public databases including Wild Ocean Whales Society (Susan MacKay), Orca Network, Spy Hopper and the Center for Whale Research. Data were analyzed with assistance from Dr. Beth Volpov. Both data chapters (Chapter 2 and Chapter 3) were written and formatted as manuscripts for submission to peer-reviewed journals. vi Table of Contents Abstract ......................................................................................................................................... iii Lay Summary ............................................................................................................................... iv Preface .............................................................................................................................................v Table of Contents ......................................................................................................................... vi List of Tables ................................................................................................................................ ix List of Figures .................................................................................................................................x Acknowledgements ..................................................................................................................... xii Dedication ................................................................................................................................... xiii Chapter 1: General Introduction .................................................................................................1 Killer whales in British Columbia .............................................................................................. 1 Population changes in the Salish Sea .......................................................................................... 2 Importance of killer whales in BC .............................................................................................. 3 Measuring marine mammal abundance and distribution ............................................................ 4 Thesis objectives ......................................................................................................................... 5 Chapter 2: The Importance of the Inside Waters of Vancouver Island for West Coast Transient Killer Whales ................................................................................................................7 Summary ..................................................................................................................................... 7 Introduction ................................................................................................................................. 8 Methods..................................................................................................................................... 11 Data collection and Study Areas ........................................................................................... 11 Data Processing .................................................................................................................... 12 Data Analysis ........................................................................................................................ 16 vii Results ....................................................................................................................................... 17 Discussion ................................................................................................................................. 26 Seasonal and Decadal Changes in Presence ........................................................................ 26 Differences in the North Island Waters and the Salish Sea .................................................. 28 Odd vs. Even Year Patterns .................................................................................................. 30 Study Strengths and Weaknesses .......................................................................................... 31 Conclusions ........................................................................................................................... 33 Chapter 3: Differential Use of Shared Habitat by Two Ecotypes of Killer Whales in British Columbia .......................................................................................................................................34 Summary ................................................................................................................................... 34 Introduction ............................................................................................................................... 35 Methods..................................................................................................................................... 37 Data collection and Study Area ............................................................................................ 37 Data Processing .................................................................................................................... 37 Data Analysis ........................................................................................................................ 41 Results ....................................................................................................................................... 42 Discussion ................................................................................................................................. 50 Changing use of the Salish Sea ............................................................................................. 51 Seasonality of Killer Whale Prey .......................................................................................... 52 Differential Use of the Salish Sea ......................................................................................... 54 Strengths and Weaknesses .................................................................................................... 55 Conclusions ........................................................................................................................... 57 viii Chapter 4: General Discussion ...................................................................................................58 Summary of Findings ................................................................................................................ 58 Project Strengths and Weaknesses ............................................................................................ 59 Future Research ........................................................................................................................ 60 Conclusions ............................................................................................................................... 62 References .....................................................................................................................................63 Appendices ....................................................................................................................................74 Appendix A Supporting tables for Chapter 2 ........................................................................... 74 Appendix B Supporting tables for Chapter 3 ............................................................................ 89 ix List of Tables Table 2.1 The number of consecutive days that matrigroups seen at least 20 times per year (Appendix A, Table A.2) were observed from 2016-2020. .......................................................... 14 Table 2.2 Annual use of the inside waters of Vancouver Island (NIW–North Island Waters and SS–Salish Sea) by transient killer whales. .................................................................................... 19 Table 2.3 Total number of transient killer whale occurrences by year and sub-area. .................. 20 Table 3.1 Total number of occurrences (occur.), individuals and number of days present for both transient killer whales (TKW) and southern resident killer whales (SRKW) from 2016-2022. .. 43 x List of Figures Figure 2.1 Map of the study area, the inside waters of Vancouver Island. Panel A shows the larger study areas, North Island Waters and the Salish Sea. Panel B shows the sub-areas referred to in the study. ............................................................................................................................... 10 Figure 2.2 The total number of transient killer whale occurrences per month in the Salish Sea and North Island Waters (N. Is. Waters) from 2016-2022 fit with a 33% span loess curve. .............. 20 Figure 2.3 The total number of transient killer whale occurrences per month in the Salish Sea separated by odd (top) and even (bottom) years, fit with a 33% span loess curve with a 95% confidence interval. ....................................................................................................................... 21 Figure 2.4 The total number of individual transient killer whales observed each month in the Salish Sea (2016-2022) separated by odd (top) and even (bottom) years. ................................... 22 Figure 2.5 Transient killer whale group size by month in the Salish Sea and North Island Waters (N. Is. Waters) from 2016-2022. ................................................................................................... 23 Figure 2.6 Transient killer whale group size by year in the Salish Sea and North Island Waters (N. Is. Waters) from 2016 to 2020 for all years combined. .......................................................... 24 Figure 2.7 The proportion of transient killer whales identified from the west-coast transient killer whale catalogue (Towers et al., 2019) that were observed per year from 2016-2020 in the Salish Sea, North Island Waters (N. Is. Waters), and both areas combined. ........................................... 25 Figure 2.8 The relationship between number of individual transient killer whales observed per month and the number of occurrences per month. ........................................................................ 26 Figure 3.1 Map of the study areas. Panel A shows the larger study area, the Salish Sea, while panel B shows the sub-areas (Strait of Georgia, Puget Sound and Juan de Fuca Strait). ............. 39 xi Figure 3.2 The total number of days transient and southern resident killer whales were observed in the Salish Sea from 2016-2022. ................................................................................................ 44 Figure 3.3 The total number of southern resident killer whale occurrences in the Salish sea per month, separated by pod from 2016-2022. ................................................................................... 46 Figure 3.4 The total number of transient killer whale occurrences per month in the Salish Sea for groups seen at least 20 times per year from 2016-2020. ............................................................... 47 Figure 3.5 Total number of consecutive days that transient and southern resident killer whale matrigroups or pods were observed in the Salish Sea. .................................................................. 48 Figure 3.6 The total number of transient and southern resident killer whales observed in groups ranging from 2 to 40 individuals in the Salish Sea. ...................................................................... 49 Figure 3.7 The total percent of year that transient and southern resident killer whales spend in the Salish Sea. ..................................................................................................................................... 50 Figure 3.8 The number of days transient and southern resident killer whales were present each month from 2016-2022 relative to the major spawning times of Pacific herring, Chinook, coho and chum salmon. ......................................................................................................................... 53 xii Acknowledgements I owe a huge thank you to my supervisor, Dr. Andrew Trites, who has supported me and my research goals since my undergraduate degree at UBC. Andrew, you not only taught me how to be a successful researcher but also how to be a good storyteller to be able to share my research with all audiences. To Dr. David Rosen, thank you for your continued support on my project throughout the past several years and thank you for always bringing kindness and humour to our conversations. I also want to thank Dr. John Ford for providing me with ideas and feedback during the initial development of my research project. Dr. Kaitlyn Gaynor, thank you for your time and interest in my project and for being my external examiner. Thank you to Jared Towers (Department of Fisheries and Oceans Canada), Erin Gless (Island Adventures Whale Watching), the Pacific Whale Watching Association (PWWA App), North Island Marine Mammal Stewardship Association, Kelley Balcolmb-Bartok and the BC Cetacean Sightings Network for your contribution of key data to this project. I also want to recognize Susan MacKay (Wild Ocean Whales Society), Orca Network, Spy Hopper and the Center for Whale Research who continue to maintain public sightings databases for researchers to use. Many thanks to Monika Shields, Jim Borrowman and Richard Beamish for their assistance on this project. To Dr. Beth Volpov and Ambre Soszynski, thank you for your help and guidance in processing my data and running my statistical analysis. Thank you, Dr. Carol Meirelles, for taking the time to teach me how to use GIS. I also want to thank Pamela Rosenbaum for keeping everything organized behind the scenes and being a great motivator in finishing my thesis. To my past and present MMRU lab members and IOF community members, thank you for your support and friendship with special thanks to Dr. Mei Sato, Julia Adelsheim, Adam Hicks, Tess McRae, Rhea Storlund, Dana Price, Brianna Cairns, Ana Pozas and Kristen Sora. I want to thank my family for your love and support throughout the last several years. To Logan, thank you for always believing in me and my research and for your constant support. Lastly, I am deeply grateful to my parents, for your unwavering support, love and encouragement which has been the driving force behind my academic journey and completion of my thesis. xiii For my parents1 Chapter 1: General Introduction Killer whales in British Columbia Killer whales (Orcinus orca) are prominent figures in the marine ecosystems of British Columbia (BC). Three distinct ecotypes of killer whales occur in BC waters: west coast transient killer whales (Bigg’s), resident killer whales and offshore killer whales. While they currently share the same species designation, each ecotype has differences in their social structures, diets and distribution patterns, among other things, which reflects the diversity of BC waters to support the three ecotypes. Additionally, the three ecotypes are genetically distinct, rarely interact and do not interbreed (Barrett-Lennard & Ellis, 2001; Bigg, 1982; Hoelzel et al., 1998; Hoelzel & Dover, 1991). West coast transient killer whales, henceforth referred to as transients, range from southern California to southeastern Alaska, and frequently travel throughout their entire range, visiting the waters of BC each year (Black et al., 1997; Dahlheim, 1997; Dahlheim et al., 2009; Ford et al., 2013; Ford & Ellis, 1999). Transients opportunistically prey on marine mammal species, primarily harbour seals (Phoca vitulina), Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lions and small cetacean species, and have been known to also prey on juvenile cetaceans such as humpback (Megaptera novaeangliae) and minke whales (Balaenoptera acutorostrata; Dahlheim & White, 2010; Ford et al., 2005; Matkin et al., 2005; Saulitis et al., 2015). Transient killer whales have dynamic group structures as individuals frequently disperse from their natal matrigroups (a female killer whale and her non-dispersed offspring, or individuals known to travel together) and travel with other individuals and matrigroups (Ford et al., 2013; Ford & Ellis, 1999). Within the resident killer whale ecotype there are two distinct populations: northern residents and southern residents. Northern resident killer whales range from northern Vancouver Island to southeast Alaska (Bigg, 1982; Krahn et al., 2004), while southern resident killer whales, are found from California to northern Vancouver Island (Bigg, 1982; Hanson et al., 2010; Krahn et al., 2004). Both resident killer whale populations only consume fish species, with Chinook salmon (Oncorhynchus tshawytscha) being the preferred prey due to its high energetic density (Ford et al., 1998; Ford et al., 2016; Hanson et al., 2010, 2021). Northern and southern 2 resident killer whales rarely interact and do not breed with each other (Bigg, 1982). Within each population, matrilines form groups called pods, and often will travel together in large groups consisting of all members of a pod (Bigg, 1982). Resident killer whale matrilines are not dynamic, and it is rare for individuals to separate from their group. Offshore killer whales are the least studied of the three ecotypes. They are distributed throughout the offshore waters of BC, ranging from southern California to western Alaska (Dahlheim et al., 2008; Ford et al., 2014). Offshore killer whales are rarely observed. As of 2012, there had only been 137 opportunistic sightings throughout their entire range (Ford et al., 2014). Therefore, little is known about the population. Genetically, they closely resemble resident killer whales (Barrett-Lennard & Ellis, 2001; Hoelzel et al., 1998) and like residents, large groups are often observed (Dahlheim et al., 2008). It is also believed that offshore killer whales prey on fish species such as salmon, sculpin, Pacific halibut (Hippoglossus stenolepis) and various shark species (Jones, 2006; Morin et al., 2006). Since few offshore individuals have been observed, little is known about group structure and the dynamics within their population. Population changes in the Salish Sea Over the past several decades, the presence of transient and southern resident killer whales in the Salish Sea, an area that includes coastal waters of southern British Columbia and Washington State, have undergone significant shifts, reflecting complex interactions between environmental changes in the area, such as prey availability and distribution, and anthropogenic influences. While transient killer whale populations and their presence in the Salish Sea continues to increase (Houghton, Baird, et al., 2015; Shields et al., 2018), use by southern resident killer whales has declined (COSEWIC, 2008; Olson et al., 2018; Shields, 2023). In the 1980’s and 90’s, transient killer whales were rarely observed in the Salish Sea, and never for extended periods (Baird & Dill, 1995; Bigg, 1982). Population estimates were also significantly lower, most likely due to limited prey availability given that harbour seals and sea lions had been culled until the 1970’s and only began to recover in numbers in the 1990’s-2000’s (Bigg, 1969; Laake et al., 2018; Olesiuk, 1999, 2018). As pinniped populations began to increase, the number of transient individuals observed in the Salish Sea also increased (Baird & Dill, 1995; Houghton, Baird, et al., 2015). Currently, transient killer whales are observed in the 3 Salish Sea year-round, and the population consists of more than 300 individuals (Shields et al., 2018; Towers et al., 2019). While transient killer whales were rarely seen in the 1980’s and 90’s, southern residents were frequently observed, particularly during summer months (May-September; Bigg, 1982; Bigg et al., 1990; Olson et al., 2018). However, use of the Salish Sea by southern residents has declined significantly in recent years, and there have been entire months with no sightings of them in BC waters (Shields, 2023). The reason for this change is most likely multifaceted, and includes changes in prey availability (Chinook salmon) and anthropogenic stressors (Ford, Ellis, et al., 2010; Holt et al., 2021; Houghton, Holt, et al., 2015; Krahn et al., 2009; Lusseau et al., 2009; Stewart et al., 2021, 2023). Documenting these changes in transient and southern resident killer whale presence is needed to understand why the changes are occurring and to mitigate future stressors and protect the Salish Sea ecosystem for both populations of killer whales. Importance of killer whales in BC Killer whales are culturally significant to Indigenous communities in BC and play an important role in their spiritual connection to the ocean. Killer whales are represented and honoured in many aspects of Indigenous culture including traditional stories, songs, dances, art, ceremonies and rituals. Some Indigenous communities have used killer whales as a status symbol as they were often associated with chiefs due to their symbolism of power and respect (Ford et al., 2000; McMillan, 2019). Many Indigenous groups have aided in the protection and restoration of killer whale populations in BC, particularly for the endangered southern resident killer whales (Guernsey et al., 2021). The continued presence of killer whales in BC waters is important for the culture of Indigenous groups and maintaining their connection to coastal areas. Ecologically, killer whales play an important role in maintaining the health and balance of BC’s marine ecosystems. As apex predators, killer whales in BC can impact populations of marine mammals and fish, particularly for their prey including harbour seals, sea lions and Chinook salmon, and may help regulate their population levels through high consumption rates (DeMaster et al., 2006; Ford & Ellis, 2006; Springer et al., 2003). Interactions between killer whales and their prey species can have significant effects throughout the food web, influencing the abundance and distribution of other marine species (Ballance et al., 2007; Branch & 4 Williams, 2007; Estes et al., 2009). Additionally, the availability of prey for killer whales in BC waters may influence their use of the area. Killer whales play a significant role in the biodiversity of coastal BC ecosystems, making their conservation essential for the overall ecological well-being of the area. In addition to their cultural and ecological importance, the presence of killer whales in BC also significantly contributes to the local economy. The charismatic nature of killer whales regularly draws tourists from around the world, who come to BC to see these marine mammals in their natural habitat. Coastal BC has become a hot spot for whale watching tours and related industries which provide abundant employment opportunities and increase overall tourism in the province (Malcolm, 2003; Teh et al., 2022). The economic value of killer whale eco-tourism highlights the need for sustainable conservation practices to ensure the continued presence of killer whales and other marine mammals in BC waters. Measuring marine mammal abundance and distribution Tracking killer whales presents unique challenges compared to terrestrial mammals due to the different nature of their environments and movement patterns. While terrestrial mammals leave tracks, scat or other physical signs that researchers can follow to study their movements, killer whales can be highly mobile, often travelling to inaccessible areas, and show no sign of their path. Although visual tracking (aerial, vessel and land-based) can be done during the day when whales are consistently followed on the water, it ends at night or in poor weather conditions due to a loss of visibility and a lack of signs as to which direction they travelled. This results in the need for a combination of monitoring methods including acoustic monitoring, satellite telemetry and visual observations, which allows scientists to track marine mammals and study their movements in an expansive ocean habitat. Data sources for transient and southern resident killer whale sightings in BC include a combination of opportunistic observations, citizen science initiatives, systematic surveys, and commercial whale watchers, and have changed significantly throughout the past several decades. In the past, sightings were generally collected by individuals living near the coastline, researchers searching for whales, or from fishermen (Baird & Dill, 1995, 1996; Bigg, 1982; Bigg et al., 1990). However, the development of technology has resulted in the majority of sightings 5 now coming from citizen scientists and whale watching companies who can collect sightings via online platforms and apps (Houghton, Baird, et al., 2015; Shields et al., 2018). The use of these citizen science contributed sightings can significantly expand the spatial and temporal coverage of transient and southern resident killer whale monitoring efforts. Combining multiple data sources provides a comprehensive understanding of the abundance and distribution of killer whales in BC waters. Thesis objectives The goal of my thesis research was to determine how two ecotypes of killer whales (transient and southern resident) use the inside waters of British Columbia, an area between mainland BC and Vancouver Island. I used sighting reports from 2016-2023 provided by researchers, industry professionals and non-profit organizations to address this question in two ways. First, I evaluated transient killer whale abundance and distribution throughout the entire inside waters. Second, I compared abundance and distribution patterns between transients and southern residents. Overall, the overarching goal of my thesis was to assess the relative importance of the inside waters of Vancouver Island and the specific areas within it, to both transient and southern resident killer whale populations. In my first data chapter (Chapter 2), I analyzed seasonal, spatial and annual patterns in transient killer whale presence. I collected sighting reports of transients and converted them into occurrences to account for repeat sightings (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018). I then used the transient occurrences to answer four questions: (i) Which individuals are present in the inside waters? (ii) What proportion of the entire BC transient population is present in the inside waters? (iii) Where are transients observed while in the inside waters? (iv) What are the seasonal patterns for transient killer whales observed in the inside waters? I expected a large proportion of the BC transient killer whale population to be observed in the inside waters with the same individuals consistently returning given that their presence in the area has increased throughout the past several decades (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018). Additionally, I expected transient killer whales to be primarily 6 observed in the Salish Sea (vs. the North Island Waters), since the area has considerable vessel traffic and research organizations (leading to increased sightings), and supports an abundant harbour seal population (Fisheries and Oceans Canada, 2010; Majewski & Ellis, 2022; Olesiuk, 1999). Lastly, I expected transient killer whales to have the highest presence in the inside waters in spring and summer months (March-September) when prey availability is highest due to the harbour seal pupping season and the Pacific herring spawn which attracts other marine mammals to the area (Keple, 2002; Temte et al., 1991; Trites, 2014). My second data chapter (Chapter 3) used my results from Chapter 2 to compare how transient and southern resident killer whales use the Salish Sea. I collected southern resident killer whale sighting reports from and consolidated them into occurrences following methods in Chapter 2 to analyze how southern resident killer whales use the inside waters. To evaluate the use of the area by each ecotype, I compared their seasonal patterns at a population level as well as at a pod and matrigroup level. I also compared the consecutive number of days an individual group was observed within each ecotype and assessed how much time transient and southern resident killer whales spend in the Salish Sea. I expected the seasonal patterns of both ecotypes to be similar as transient killer whale prey and southern resident killer whales rely on salmon and other key fish species spawning seasons for food (Ford et al., 1998; Hanson et al., 2010; Thomas et al., 2017, 2022). In terms of number of days present in the Salish Sea, I expected southern resident killer whale pods to be in the area for more consecutive days than transient killer whales as, historically, southern residents have spent the majority of summer months in the Salish Sea (Bigg, 1982; Bigg et al., 1990; Olson et al., 2018), while transient killer whale matrigroups have only been observed up to six consecutive days in the Salish Sea (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018). Lastly, I expected transient killer whales to have an increasing presence in the Salish Sea due to increased pinniped numbers and high amounts of available prey. However, I expected that southern resident killer whales would overall have a lower annual presence than transient killer whales because their numbers have declined for several years, in tandem with Chinook salmon stocks (COSEWIC, 2008; Species at Risk Act, 2002). Both data chapters are written as stand-alone manuscripts to be published in peer-reviewed scientific journals. As a result, there is some overlap in the content of each chapter. 7 Chapter 2: The Importance of the Inside Waters of Vancouver Island for West Coast Transient Killer Whales Summary West coast transient killer whales (Orcinus orca) range from central California to southeastern Alaska as they search for marine mammal prey. However, knowledge of how this wide-ranging population uses coastal areas of western North America, and the relative seasonal importance of different portions of their range, are poorly understood. Using sighting reports of transient killer whales from researchers, conservation organizations and whale watching companies from 2016 to 2023, I assessed the seasonal distribution and abundance of transient killer whales that feed in the inside waters of Vancouver Island, BC (an area that includes the Salish Sea and North Island Waters off northeastern Vancouver Island). I discovered that consistent numbers of individuals and matrigroups (a female killer whale, her non-dispersed offspring and individuals known to travel with this group) visited the inside waters each year with median group sizes of 5 in the Salish Sea, and 4 in North Island Waters. Transient killer whales were present year-round and were seen an average of 250 days each year. Seasonally, they were observed most frequently in the Salish Sea between June and September but returned in lower numbers during the month of July in even years. The highest number of transient occurrences in the North Island Waters was in September. In terms of individuals present, peak numbers occurred from March to September, concurrent with seasonal increases in their primary prey populations of seals and sea lions. Overall, approximately 70% of the BC west coast transient killer whale population travels through and hunts in the inside waters of Vancouver Island each year. This unexpectedly high proportion of the population suggests that the Salish Sea and North Island Waters are particularly important for the survival of transient killer whales, and points to the need to determine the relative importance of other key feeding areas throughout their range from central California to southeastern Alaska. 8 Introduction Transient killer whales (Orcinus orca; aka Bigg’s killer whales) are commonly observed along the coast of British Columbia (BC) where they prey predominately upon marine mammals such as harbour seals (Phoca vitulina), Steller sea lions (Eumetopias jubatus) and harbour porpoise (Phocoena phocoena; Ford et al., 1998, 2013). This population of killer whales, known as the west coast transient population, ranges from southern California to southeast Alaska, and numbered an estimated 349 individuals in 2018 (Towers et al., 2019). Individuals frequently travel throughout their entire range (Ford et al., 2013; Ford & Ellis, 1999), but appear to be more consistently seen in some parts of it than others. Most of the reported sightings of transient killer whales in BC have occurred in the inside waters of Vancouver Island, an area that includes the Salish Sea and North Island waters (Ford et al., 2013). However, how and when transient killer whales use the inside waters of Vancouver Island is poorly understood. Little research has been conducted to determine habitats of special importance for transient killer whales. Transient killer whales are seen year-round in Alaska, British Columbia and California, with notable seasonal peaks—consistent with seasonal coastal changes in pinniped populations and other prey species (Black & Ternullo, 2009; Dahlheim et al., 2009; Dahlheim & White, 2010; Ford et al., 2013; Ford & Ellis, 1999; Matkin et al., 2007; Shields et al., 2018; Towers et al., 2019). They form dynamic matrigroups (a female killer whale and her non-dispersed offspring and individuals known to travel with this group, or individuals who are known to travel together), with individuals frequently separating from their matrigroups for varying periods of time (Ford et al., 2013; Ford & Ellis, 1999). Some matrigroups seem to prefer certain coastal areas more than others suggesting they may have varying home ranges and potentially different prey preferences (Ford et al., 2013; Ford & Ellis, 1999). However, their seasonal and spatial use of each region, and therefore the importance of each, are not well understood. Most of the BC sightings of transient killer whales have come from the inside waters of Vancouver Island, a semi-enclosed coastal area that spans BC and Washington State (Figure 2.1; Ford et al., 2013). These waters include the Salish Sea and North Island waters, where sightings of transient killer whales have increased from rare, infrequent encounters in the 1970s and 1980s, 9 to daily encounters in more recent years (Baird & Dill, 1995; Ford et al., 2013; Ford & Ellis, 1999; Houghton, Baird, et al., 2015; Shields et al., 2018; Towers et al., 2019). Over the past several decades, transient presence in the Salish Sea has been increasing, particularly during summer months (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018). This increase in sightings and numbers of transient killer whales in the inside waters may reflect an overall increase in the size of the transient killer whale population—combined with the recovery of prey populations following the protection of pinnipeds in the early 1970s. The west coast transient killer whale population is listed as threatened under the Canadian Species at Risk Act because of their small population and their predisposition to threats such as contaminants, and acoustic and physical disturbance (COSEWIC, 2008; Fisheries and Oceans Canada, 2007). Identifying important areas for feeding, socializing, resting and reproduction is needed to ensure their survival and conservation—and ensure efficient population management (Ford et al., 2013; Hiers et al., 2016; Shields, 2023). Identifying core habitat also provides information on the potential effect that changes in the ecosystem and the availability of prey may have on the population. Unfortunately, information is limited on how transient killer whales use the entire inside waters of Vancouver Island, which is valuable for assessing how they may be affected by potential ecosystem changes, such as the proposed culling of seals and sea lions (Nelson et al., 2020). The aim of my research was to determine the recent distribution and abundance of transient killer whales using the inside waters of Vancouver Island. I analyzed sighting reports of individual whales identified from 2016-2023 to determine where and how many transient killer whales were present—as well as how much time they spent in the area, and the proportion of the west coast transient population that relied on the inside waters of Vancouver Island. Seasonal and yearly abundance trends were also analyzed, as well as matrigroup size differences which could reflect prey availability and preference. This analysis of sightings reports contributes to the conservation of transient killer whales by establishing the relative importance of the inside waters of Vancouver Island for the transient population. 10 Figure 2.1 Map of the study area, the inside waters of Vancouver Island. Panel A shows the larger study areas, North Island Waters and the Salish Sea. Panel B shows the sub-areas referred to in the study. 11 Methods Data collection and Study Areas Sighting reports from 2016-2023 of transient killer whales within the inside waters of Vancouver Island, Canada (Figure 2.1), were collected into a preliminary database (see Data Processing). The inside waters included the coastal waters of BC and Washington State from the western end of the Juan de Fuca Strait (48.49, -124.73) to the northwestern mouth of Queen Charlotte Strait (51.04, -127.85). Sightings came from public and private databases including the Department of Fisheries and Oceans Canada (DFO), the Pacific Whale Watching Association (PWWA), the BC Cetacean Sighting Network (BCCSN), Wild Ocean Whales Society (WOWS), North Island Marine Mammal Stewardship Association (NIMMSA) and individual researchers and industry professionals. Public databases were considered easily accessible online sighting reports, generally from citizen scientists, while private databases were collected by individual researchers or organizations and were not publicly posted. Each reported sighting of transient killer whales included dates, locations, latitudes, and longitudes (see Data Processing). Many reports also identified individuals present, total numbers of individuals, and confidence of identifications. Additional sightings from Orca Network (April – June 2020) were added to increase the number of sightings during the COVID-19 pandemic when research was halted and whale watching companies were restricted from operating. Latitude and longitude were not provided for most of these sightings but were derived from photos and the description of the location. While various aforementioned sources were used from 2016 – 2020, only sightings recorded by the PWWA were used for 2021, 2022 and 2023—and analyses for these years were restricted to the Salish Sea where the PWWA primarily operates as data were missing for the North Island Waters. All transient killer whales photographed in BC waters have individual names consisting of alphanumeric labels delineated with the letter ‘T’ followed by a number that represents the order that they were identified within the population. For example, T036 is the 36th individual transient ever identified (Bigg, 1982). Matrigroups are identified by the head female of the group, and each of her offspring are designated by their mother’s identification number followed by the letters A, B, C etc. For example, T036A would be T036’s first offspring. Each of the 12 photographically identified west coast transient killer whales are contained in a 2019 catalogue that includes names and photographs of over 300 individuals that have been seen in BC waters (Towers et al., 2019). Data Processing Using the most recent catalogue of photographically identified whales (Towers et al., 2019) as my baseline for the transient killer whale population, I removed reported sightings of individuals from the sightings database that did not have a ‘T’ designation. This included unknown ecotype (‘U’ designation) or transients that had a California (‘CA’) designation. I also removed some individuals that had a ‘T’ designation but were not in the catalogue, unless they were a calf of a known transient killer whale who was in the catalogue (Appendix A, Table A.1). Individuals with a ‘T’ designation who were not in the catalogue may have been new to the area since 2019 and would have come from other transient killer whale populations (Black et al., 1997; Dahlheim, 1997; McInnes et al., 2021). I also removed all sighting reports from public databases that had no supporting photographs or contained low-quality photographs that could not be used to identify individual transient killer whales. However, I kept sighting identifications without associated photos from private databases that were provided by researchers or industry professionals who had substantial knowledge of the transient killer whale population and could confidently identify individual whales. Additionally, I removed both unconfirmed identifications (e.g. “T018? T019?”, etc.) and low confidence identifications. For all sightings from the public databases that had photos, I verified the identifications made by the observers by comparing the photos taken during the encounter with the established west coast transient killer whale catalogue (Towers et al., 2019). For all sightings, I listed which killer whales were identified and the total number of individuals present. For public sightings accompanied with photos, I only recorded the individuals photographed, and did not assume that other individuals in the matrigroup were present. I did so because transient killer whale groups are dynamic, and members frequently disperse from their matrigroups. However, if a matrigroup was listed in a sighting from a private database, I assumed that all members of the listed matrigroup were present, unless otherwise stated. For 13 example, if a sighting of the T101’s was made by a researcher or industry expert (private database), I assumed that all 3 members of their matrigroup were present unless there was a note such as “T101’s except T101A”. However, if only 2 members of the T101’s were photographed in a sighting from a public database, I would only record 2 individuals as being present and would not assume that the third member was also present. I based all matrigroups assignments according to the matrilineal groups classified in the 2019 west coast transient photo identification catalogue (Towers et al., 2019). Identifications were separated into group and individual ID’s, where a group is a known transient matrigroup, and an individual is a whale that travels alone and is not associated with a matrigroup. I also listed all identifications of all whales present as encounter ID’s. If the entire matrigroup was not present during a sighting, they were not listed under group ID and were instead only listed as an encounter ID. For some years, individuals who are known to travel alone were listed as a group when they had offspring. Additionally, if a female and her offspring separated from their matrigroup, and was classified as a new matrigroup in the DFO sightings database, I included the new matrigroup as a separate group ID. I also assumed that all whales identified were present throughout the entire encounter, and that group size equaled the total number of individuals identified in the encounter. In cases where I used photographs to verify the number of individuals present, the group size could be larger than reported if individuals were present but not photographed. Area and sub-area were added for each sighting using the recorded latitude and longitude that accompanied each sighting report. Area was designated as either North Island Waters or Salish Sea (Figure 2.1A), and sub-area designations were Queen Charlotte Strait, Johnstone Strait, Strait of Georgia, Juan de Fuca Strait and Puget Sound (Figure 2.1B). 14 Table 2.1 The number of consecutive days that matrigroups seen at least 20 times per year (Appendix A, Table A.2) were observed from 2016-2020. Consecutive days observed were separated by area, the North Island Waters and the Salish Sea. Matrigroups were usually not seen over consecutive days, but were occasionally present for up to 13 consecutive days. All consecutive days in this table were counted during summer months, May-September, when sighting effort was the highest. # of days observed consecutively 2016 2017 2018 2019 2020 Overall Proportion of frequency distribution 1 60 128 122 234 82 626 58.18% 2 24 49 46 71 28 218 20.26% 3 7 22 19 42 16 106 9.85% 4 6 17 9 21 8 61 5.67% 5 0 3 8 11 7 29 2.70% 6 1 6 5 1 2 15 1.39% 7 1 1 0 0 1 3 0.28% 8 0 2 3 2 2 9 0.84% 9 0 0 1 1 2 4 0.37% 10 0 0 1 0 0 1 0.09% 11 0 0 0 0 2 2 0.19% 12 0 0 0 1 0 1 0.09% 13 0 0 1 0 0 1 0.09% 15 For the Salish Sea and North Island Waters, I separated transient killer whale sightings into occurrences to account for repeat sightings of the same group and differences in sightings effort. I defined an occurrence as a unique group of transient killer whales that had not been previously seen that day. A unique group could be 1) a single matrigroup, 2) an individual who travels solitarily, 3) multiple matrigroups or 4) a combination of matrigroups and individuals. Occurrences were limited to one per unique group per day, regardless of the number of sightings of that unique group in a single day. Preliminary analysis of the number of consecutive days that frequent users of the North Island Waters or the Salish Sea (i.e., transient killer whale matrigroups seen more than 20 times per year; Table A.2) were present revealed that they were primarily only observed for one consecutive day (Table 2.1). To ensure that this was not biased by seasonal differences in sightings effort, the consecutive days count was completed for summer months only (May through September) when effort level was the highest and it was unlikely for a group to be missed. Using single day occurrences is also consistent with analyses undertaken by others (e.g., Hauser et al., 2007; Hauser et al., 2006; Olson et al., 2018). In terms of numbers of individual whales present, I used the sighting with the highest number reported for a given day. For example, if there was one sighting of T100, T100C, T100E, T100F, T100B and T100B1, and another sighting of T100, T100B and T100B1, I used the first sighting (e.g., 6 individuals) regardless of the time of day the sightings occurred. I also used the sighting with the most information provided and from the most reputable source if there were multiple sightings of the same group—and used the first sighting of the day if there were multiple sightings from the same source and time of sighting was provided. If there were individuals seen in the same day but were reported with different individuals who had not yet been seen that day, both sightings were kept. For example, if Sighting 1 included T101, T102, T101A, T101B, T099, and T099B and Sighting 2 included T101, T102, T101A, T101B, and T087, I included both sightings if T099, T099B and T087 had not otherwise been observed that day (e.g., 2 separate occurrences). For each month, year, and area, I counted the total number of matrigroups and individuals as well as the total number of days that transient killer whales were observed. Total number of occurrences per month and year were tallied to determine seasonal trends and changes over the study period. I also recorded which matrigroups and individuals were present in the inside waters 16 of Vancouver Island each year to determine whether new individuals were coming to the area, and to determine which groups used the area the most. To determine the total proportion of the population present in the inside waters of Vancouver Island, I counted and tallied all individuals in the 2019 west coast transient killer whale catalogue, including individuals born in that year—and excluded all individuals who had been confirmed dead that year. This count was done for every year from 2016-2020, but not for 2021-2023 because sightings only included those in the Salish Sea, and were unavailable from other sources. Data Analysis The database was compiled using Microsoft Excel (version 16.43) and analyzed using R (version 4.2.0) and R studio (version 1.3.1093). For all analyses, I used non-parametric statistical tests because the data were not normally distributed. For group size, I used the total number of individuals observed per occurrence to determine the mean, mode and the range for each year and area within the year (North Island Waters vs. Salish Sea). To analyze the relationship between group size and month, I used a Kruskal Wallis test to check for an overall effect of “month” within each area, with a post-hoc Dunn test with Bonferroni correction to test for differences between pairs of months. When analyzing for differences in group size per month between the North Island Waters and the Salish Sea, I used a Wilcoxon rank sum test (also known as a Mann Whitney U test). Both areas were grouped by month and the p-values were adjusted post-hoc using the Bonferroni method to account for multiple tests. For the relationship between group size by area and year, I analyzed the data using a Kruskal Wallis test with a post-hoc Dunn test. To test for differences in group size per year between the North Island Waters and the Salish Sea, I used a Wilcoxon rank sum test with the data first grouped by year and adjusted the p-values using the Bonferroni method. I also used the Wilcoxon rank-sum test to test for differences in group size between the two areas with all years combined. I tallied the total number of occurrences per month and area and tested for seasonal and yearly differences using the Kruskal Wallis test and Dunn test with Bonferroni correction. To test for overall differences in the total number of occurrences and occurrences per month between the two areas, I used a Wilcoxon rank sum test. I also compared the total number of 17 individuals observed per year and area (North Island waters and Salish Sea) using the Kruskal Wallis test. Comparisons in the total number of occurrences and individuals per month between odd and even years were analyzed using the Kruskal Wallis test with post-hoc Dunn test with Bonferroni correction. To assess whether significant changes occurred over time in the percent of transient killer whales present per year, I used a generalized linear model for each individual area (North Island Waters and Salish Sea) and both areas combined. The total number of occurrences for each sub-area (Queen Charlotte Strait, Johnstone Strait, Strait of Georgia, Juan de Fuca Strait and Puget Sound) was also tallied to determine which sub-area the majority of the sightings came from. When testing the relationships between total number of occurrences and total number of individuals per month for odd and even years, only data from the Salish Sea from 2016-2023 were analyzed as data were missing from the North Island Waters for 2021-2023. Similarly, group size data only included occurrences from 2016-2020 when testing for differences between areas. To evaluate effort, the relationship between the number of occurrences and number of individuals observed was analyzed. Since there are more boats on the water in summer months (May-October) which may account for more sightings, the number of individuals observed per month was compared to the number of occurrences per month to see if the number of individuals increased when there were more occurrences, or if the same individuals were repeatedly being observed and recorded. Conducting this test also evaluated the relationship between number of occurrences and number of individuals present in months where search effort is lower (November-April). A generalized additive model was used as there was a non-linear relationship between occurrences and individuals. Data from 2016-2022 and all areas were used for the generalized additive model. Results There were 3,640 occurrences of transient killer whales in the inside waters of Vancouver Island from 2016-2020—an average of 729 occurrences per year (Table 2.2). Annual numbers of occurrences differed significantly between the North Island Waters and the Salish Sea (p < 0.05; 18 Table A.3). Most sightings of transients occurred in the Strait of Georgia within the Salish Sea (Table 2.3), which accounted for 3,076 occurrences compared with 564 occurrences in the North Island Waters (p < 0.001). Within each area, there were no significant differences in number of occurrences between years (Table A.4; NIW Kruskal Wallis c2= 3.25, df = 4, p = 0.52; SS Kruskal Wallis c2 = 1.58, df = 4, p = 0.81). In terms of numbers of days present (2016-2020), transients were seen an average of 249 days per year (68% of each year) in the inside waters of Vancouver Island (Table 2.2). Transients occurred more frequently in the Salish Sea (present for an average 231 days or 63% of the year) than in the North Island Waters (present for on average 89 days or 24% of the year). Occurrences of transient killer whales differed significantly by area for every month (p < 0.05; Figure 2.2; Table A.5) except for December when there was no significant difference in number of occurrences between the two areas. In the Salish Sea, the occurrences of transients were highest from June to September—while in the North Island Waters, occurrences peaked in September (Figure 2.2). Overall, occurrences of transient killer whales were relatively low in the North Island Waters, and showed a significant difference in number of occurrences per month between September (average 24) and each of the winter months (November, December, January, February; average 3; p < 0.05; Figure 2.2; Table A.6). Similarly in the Salish Sea, occurrences differed significantly between most winter (November- February) and summer months (June - September; p < 0.05; Figure 2.2; Table A.6). Comparing occurrences and numbers of individuals present between months showed greater variation during July than any other month of the year in the Salish Sea (Figure 2.2). Closer inspection revealed an odd versus even year difference, whereby transient killer whale occurrences were higher in the Salish Sea during odd years (2017, 2019, 2021, 2023) than during even years (2016, 2018, 2020, 2022) in July (Figure 2.3; W = 0, p < 0.05). A similar pattern was also noted in terms of numbers of individuals seen each year (Figure 2.4), but this was not statistically significant (W = 9.5, p = 0.29). 19 Table 2.2 Annual use of the inside waters of Vancouver Island (NIW–North Island Waters and SS–Salish Sea) by transient killer whales. The table shows total number of occurrences (ocurr.), matrigroups, and known individuals (individ.)—as well as the proportion of the total population seen, days present, and mean, mode and range of group sizes. Occurr. Matri-groups Known Individ. Total seen (% of population) # of days present (% of year present) Mean group size ± SE Mode group size Range of group size 2016 519 57 21 220 (70%) 230 (63%) 5.90 ± 0.19 4 1-26 NIW 99 42 13 159 (50%) 78 (21%) 4.82 ± 0.31 4 1-26 SS 420 49 20 192 (61%) 206 (56%) 6.16 ± 0.22 4 1-26 2017 742 60 26 246 (75%) 238 (65%) 6.43 ± 0.17 5 1-31 NIW 87 27 12 116 (35%) 71 (20%) 4.72 ± 0.32 5 1-24 SS 655 57 28 236 (72%) 229 (63%) 6.66 ± 0.18 4 1-31 2018 743 56 23 237 (68%) 260 (71%) 5.95 ± 0.14 4 1-24 NIW 109 35 18 150 (43%) 94 (26%) 4.56 ± 0.25 5 1-14 SS 634 45 23 196 (56%) 236 (65%) 6.19 ± 0.15 4 1-24 2019 899 58 28 255 (69%) 263 (72%) 6.44 ± 0.15 4 1-31 NIW 133 43 25 193 (52%) 101 (28%) 5.56 ± 0.32 4 1-30 SS 766 48 29 215 (58%) 245 (67%) 6.60 ± 0.17 4 1-31 2020 737 59 33 278 (76%) 255 (70%) 6.43 ± 0.15 4 1-27 NIW 136 42 16 182 (50%) 100 (27%) 5.94 ± 0.39 4 1-27 SS 601 51 36 252 (69%) 241 (66%) 6.54 ± 0.16 4 1-27 All Years (2016-2020) 3640 72 36 326 1246 (68%) 6.26 ± 0.07 4 1-31 NIW 564 62 28 245 444 (24%) 5.20 ± 0.15 4 1-30 SS 3076 67 35 277 1157 (63%) 6.46 ± 0.08 4 1-31 20 Figure 2.2 The total number of transient killer whale occurrences per month in the Salish Sea and North Island Waters (N. Is. Waters) from 2016-2022 fit with a 33% span loess curve. In the Salish Sea, occurrences were highest through summer months, particularly in June, August and September, while North Island Waters occurrences peaked in September. Table 2.3 Total number of transient killer whale occurrences by year and sub-area. 2016 2017 2018 2019 2020 North Island Waters Queen Charlotte Strait 28 29 30 36 58 Johnstone Strait 71 58 79 97 78 Salish Sea Strait of Georgia 273 391 453 527 335 Juan de Fuca Strait 131 235 149 203 171 Puget Sound 16 29 32 37 95 21 Figure 2.3 The total number of transient killer whale occurrences per month in the Salish Sea separated by odd (top) and even (bottom) years, fit with a 33% span loess curve with a 95% confidence interval. Occurrences were high through summer months (June – September) of odd years, but show a distinct drop during July of even years. 22 Figure 2.4 The total number of individual transient killer whales observed each month in the Salish Sea (2016-2022) separated by odd (top) and even (bottom) years. The numbers of individuals in the area increased from March–September in odd years, but decreased in July of even years. Both panels are fit with a 33% span loess curve with a 95% confidence interval. 23 Figure 2.5 Transient killer whale group size by month in the Salish Sea and North Island Waters (N. Is. Waters) from 2016-2020. All data points were jittered and fit with a 33% span loess curve. Groups larger than 15 individuals (n = 171) were removed from the figure but included in analysis. The median group size in the Salish Sea ranged from 4-7, while median group size in North Island Waters ranged from 4-5. From 2016-2020, group sizes of transient killer whales ranged from 1 to 31 individuals. Group sizes were relatively constant throughout the year in the North Island Waters (p > 0.05), but varied slightly between peak summer (June and July) and other months (March, September, October, November; p < 0.05; Figure 2.5; Table A.7). On average, groups consisted of 6 individuals in the Salish Sea and 5 individuals in the North Island Waters, with an overall mode of 4 individuals per group (Table 2.2). Group sizes were significantly larger in the Salish Sea than in the North Island Waters in June, August, September and October (p < 0.05; Figure 2.5; Table A.9) and throughout all years, except 2019 (Figure 2.6; Table A.8). 24 Figure 2.6 Transient killer whale group size by year in the Salish Sea and North Island Waters (N. Is. Waters) from 2016 to 2020 for all years combined. Group sizes larger than 30 individuals (n = 2) were removed from the figure but included in the analysis. Overall, the median group size was 5 individuals in the Salish Sea, and 4 in the North Island Waters. On average, 247 unique individuals were observed per year in the inside waters of Vancouver Island from 2016-2020. This represents approximately 71% of the approximately 346 individuals that have been identified in BC as belonging to the west coast transient killer whale population during our study period (Table 2.2; Towers et al., 2019). In terms of regions, an average of 160 individuals (46% of transient population) were observed in the North Island Waters throughout the study period, while the Salish Sea had an average of 218 individuals present (63% of the population). While more transients were observed in the Salish Sea compared to the North Island Waters (Table 2.2), 69% of all 326 identified whales used both areas (Table A.10). The total number of individuals seen each year was relatively constant (Kruskal Wallis c2 = 1.7, df = 4, p > 0.05), but varied between months, with more individuals present in the inside waters of Vancouver Island during summer (June, August, September) than winter months (January, February, December; Table A.11). 25 Figure 2.7 The proportion of transient killer whales identified from the west-coast transient killer whale catalogue (Towers et al., 2019) that were observed per year from 2016-2020 in the Salish Sea, North Island Waters (N. Is. Waters), and both areas combined. Overall, an average of 71% of the whales used the inside waters of Vancouver Island, and there was no significant difference between years. Of the approximately 247 unique individuals that returned each year to the inside waters, 233 of them were present in each of our 5 years of study (2016-2020). They consisted of 43 matrigroups and 20 lone individuals (Table A.12). The annual newcomers (approximately 14 per year who had not been seen in the inside waters in the previous year from 2017-2020) consisted of 5-8 matrigroups and 4-10 lone individuals (Table A.13). Overall, the proportion of the transient population that used the North Island Waters and the Salish Sea was relatively constant throughout the study period. Year had no effect on percent of population present (2016-2020, p > 0.05; Figure 2.7; Table A.14), but area did significantly affect the model (p < 0.01, Table A.14). There was a significant relationship between number of occurrences and number of individuals observed (p < 0.001, R2 = 0.87, Table A.15). The relationship between the two was proportional until approximately 25 occurrences (Figure 2.8), at which point the rate of increase in the number of individuals per number of occurrences decreased and began to plateau around 100 occurrences at just over 100 individuals. 26 Figure 2.8 The relationship between number of individual transient killer whales observed per month and the number of occurrences per month. The data were fit with a loess curve with a 95% confidence interval and a 75% span. Discussion Transient killer whales used the inside waters of Vancouver Island year-round during all years of study (2016-2020), but occurred more frequently in the Salish Sea compared to the North Island Waters. Seasonally, transient killer whales had higher occurrences from June to September in the Salish Sea, and were at their highest occurrences during September in the North Island Waters. While sightings of transients were high every summer in the Salish Sea, they were significantly lower during every July of even years. However, it is unclear why their presence in the Salish Sea should differ between odd and even years. Approximately 70% of the west coast transient killer whale population used the inside waters of Vancouver Island in any given year. While some members of the population did not return every year, the majority did. Seasonal and Decadal Changes in Presence Little is known about the historic presence of transient killer whales in the inside waters of Vancouver Island. The earliest studies of transient killer whales reported just 14 encounters 27 over a single year in the Salish Sea in the late 1980’s (excluding Puget Sound), and 50 encounters in the early 2000’s (Baird & Dill, 1995; Houghton, Baird, et al., 2015). Transient killer whales were considered rare visitors to the Salish Sea compared to the fish-eating resident killer whales. In contrast to the low numbers reported in the Salish Sea from the 1980s to early 2000s (≤50), annual occurrences of transients averaged 615 per year from 2016-2020 (which includes an average of 42 annual occurrences in Puget Sound). Note, however, that the previous research tallied occurrences every six days, meaning that if the same group was observed for up to six days in a row, that was one single occurrence (e.g., Baird & Dill, 1995; Houghton et al., 2015). Overall, the numbers of transient killer whales returning to the Salish Sea each year were relatively constant during all 5 years of my study (2016-2020), and accounted for approximately 70% of the entire BC west coast transient killer whale population. This is a marked change from the 1980s and 1990s, and suggests that the Salish Sea has become increasingly important habitat for this population of transient killer whales. In addition to decadal increases in transient killer whale presence in the Salish Sea, there have also been notable seasonal changes in their presence. Initially, transient killer whales were primarily observed in the Salish Sea in August and September during the 1980’s and 1990’s—and later began being reported in other months of the year starting in the 2000’s, with notable peak encounters in April and May (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018). Today, they can be found year-round, with notable increases beginning in March, peaks in June and August, and decreases in presence starting in October (Figures 2.2 and 2.4). Thus, transient killer whales spend more time in the inside waters of Vancouver Island during spring and summer, than in winter months. Another notable decadal change has been the increasing numbers of matrigroups coming to the Salish Sea. Many matrigroups that had not been observed in the Salish Sea during the 1980’s and 1990’s, began being seen in the 2000’s (Houghton, Baird, et al., 2015). This increase in new matrigroups included those commonly seen between Washington and California, and others coming from Alaska and northern BC (Shields et al., 2018). During my study period, 24 individuals who were not in the west-coast transient killer whale catalogue (Towers et al., 2019), were observed in the inside waters of Vancouver Island. The majority of these new individuals 28 were observed in the Salish Sea, and most likely spend the majority of their time off the coast of California as part of the California transient killer whale population (Black et al., 1997; California Killer Whale Project, 2023; McInnes et al., 2021). There is no universal naming system for transient killer whales, and some individuals have been included in more than one population under different names. The increasing numbers of transient killer whales in the Salish Sea presumably reflects a combination of increased growth of the transient killer whale population, which since 2019 had increased 4.1% per year since 2012 (Towers et al., 2019), and local increases in the amount and predictability of prey. While in BC waters, transients primarily feed on harbour seals, followed by harbour porpoises and Steller sea lions (Ford et al., 1998, 2013). The decadal and seasonal changes in transient killer whale use of the inside waters of Vancouver Island is likely due in part to significant increases in harbour seal, California sea lion (Zalophus californianus) and Steller sea lion populations. In the early 1900’s, seal and sea lion populations were reduced to low numbers from hunting and culling, but have increased since being protected in the early 1970’s in Canada and the United States (Fisheries and Oceans Canada, 2010; Laake et al., 2018). Harbour seal populations in BC increased from approximately 10,000 individuals in 1970, to 105,000 individuals in 2010, while California and Steller sea lion populations have more than tripled in the four decades following protection (Fisheries and Oceans Canada, 2010; Olesiuk, 1999, 2018). While sea lion populations are still increasing in BC, harbour seal populations have been considered to be at carrying capacity since 2000 (Chandler et al., 2017; Olesiuk, 1999). The Strait of Georgia, a region which comprises the majority of the Salish Sea, has the highest density of harbour seals in BC with an estimated 39,000 individuals in 2014 (DFO, 2022; Majewski & Ellis, 2022). The increase in transient killer whale presence, both decadal and seasonal, highlights the importance of prey species and their availability in the inside waters of Vancouver Island to transient killer whales. Differences in the North Island Waters and the Salish Sea Throughout the study period (2016-2020), there were significantly more sightings and individuals in the Salish Sea compared to the North Island Waters, which may be due to differences in sighting efforts, but likely reflects regional differences in prey densities and availability. Similarly, the highest presence of transients in June and August in the Salish Sea, 29 and their highest presence in September in the North Island Waters most likely correspond to different seasonal peaks in prey availability in the two areas. Steller sea lions occur year-round in the inside waters, but a greater number arrive every spring (March, April, May) to prey on spawning Pacific herring (Clupea pallasii; Hay & McCarter, 2013; Keple, 2002; Olesiuk, 2018; Schweigert et al., 2010). Similarly, many male California sea lions travel north from California to the Salish Sea every fall and peak in abundance in the spring (DFO, 2023; Keple, 2002). Like Steller sea lions, harbour seals are available for killer whales to consume year-round. Their pupping season occurs in July and August in the inside waters of Vancouver Island, with weaning in September (Burg et al., 1999; Temte et al., 1991). Transient killer whales most likely return to the Salish Sea in increasing numbers in spring to target both sea lion species– and remain at high numbers through summer due to the high densities of harbour seals and the addition of naïve newborn pups. Among the transient population, some matrigroups showed preference for either the North Island Waters or the Salish Sea, while other groups travelled between the two areas. Five matrigroups and three solitary individuals (19 individuals total) were only observed in the North Island Waters. In contrast, 51 individuals (9 matrigroups and 12 lone individuals) were only observed in the Salish Sea. Many groups travelled between the two areas spending a large portion of the year in the inside waters such as the T002C’s who were primarily found in the North Island Waters and northern Salish Sea, but travelled annually to the southern Salish Sea. In total, 226 individuals were observed in both the North Island Waters and the Salish Sea, with 245 individuals (approximately 71% of population) observed in the north and 277 individuals (approximately 80% of population) in the Salish Sea. The differences in use of the two areas suggests that the groups may have different habitat preferences and specialization in prey species consumed. However, other groups of transients were more nomadic, and frequently travelled throughout their entire range (California to Alaska), spending a short time in each area. Group sizes were larger in the Salish Sea compared to the North Island Waters, which may be related to the availability of different prey types in each area. Larger transient killer whale groups are often observed when they target larger marine mammals such as juvenile whales, Pacific white-sided dolphins and adult male Steller sea lions—whereas smaller groups may be more cost effective when matrigroups hunt smaller-sized species such as harbour seals 30 (Baird & Dill, 1996; Dahlheim & White, 2010). Group sizes of transients were largest in the Salish Sea (31 individuals) which might also reflect socialization and potential mating opportunities between matrigroups (Baird & Dill, 1996). Odd vs. Even Year Patterns Transient killer whale presence in the Salish Sea decreased every July during even years, and returned to normal levels in odd years (Figure 2.3). The number of individual whales observed also decreased slightly each July during even years, but was not statistically significant. This apparent difference between killer whale presence during July of odd and even years may be tied to the two-year life cycle of pink salmon, which are believed to significantly affect the dynamics of multiple species and trophic levels across the North Pacific (Ruggerone et al., 2019, 2023). Pink salmon have a fixed two-year life cycle that sees them returning to spawn in northern or southern BC from July to September in alternating years (Heard, 1991). In the Salish Sea, pink salmon primarily spawn in odd years, and return in negligible numbers in even years (Heard, 1991). Elsewhere in parts of northern BC and Alaska, pink salmon tend to spawn in greater numbers during even years (Heard, 1991). For example, pink salmon returns to the Salish Sea have averaged 18 million in odd years and 0.4 million in even years (Ruggerone et al., 2023). During my study period, pink salmon returning to the Fraser River averaged 7 million in odd years and were inconsequential in even years (Pacific Salmon Commission, 2018, 2021, 2023). In contrast, numbers spawning in northern BC averaged 1.7 million in even years and 0.7 million in odd years (Government of Canada; Fisheries and Oceans Canada, 2023). One reason why there may be more killer whales present in July of odd years when pink returns are their highest is that there are higher aggregations of pinnipeds and small cetaceans feeding on pink salmon. Pinnipeds such as harbour seals and sea lions are opportunistic feeders that respond to seasonal increases of available prey species (Olesiuk et al., 1990; Sigler et al., 2009; Thomas et al., 2017). The increase and potential ease of targeting pinniped species gathered in the same area could draw transient killer whales into the Salish Sea in odd years or out to northern areas of BC and Alaska in even years. 31 Another hypothesis for how the pink salmon spawn could account for the change in transient presence is that certain marine mammal species may follow and target the returning pink salmon in the Salish Sea during odd years when concentrations are highest, such as Pacific white-sided dolphins. Transient killer whales may be aware of this change that happens every other year and may follow the pink salmon spawn, to prey on marine mammals that travel to prey on the salmon. A third hypothesis to explain the biennial transient killer whale pattern could be related to southern resident killer whales who appear to chase off transients during the few times the two ecotypes have been seen to interact (Baird & Dill, 1995; Bigg, 1982; Morton, 1990)– and whose presence may also be affected by pink salmon (Ruggerone et al., 2023). Trends in Chinook salmon abundance in BC and Alaska (the preferred prey of southern resident killer whales) have been opposite to those of pink salmon trends, and body sizes of chinook have decreased as pink salmon numbers increased (Losee et al., 2019; Ruggerone et al., 2023). This may have led to reduced consumption of Chinook in odd years (during years of high pink returns) and explain a biennial pattern in birth and mortality rates of resident killer whales (1998-2020; Ruggerone et al., 2019), Thus there may be fewer southern resident killer whales present in July during years when pink returns are high and there are fewer Chinook available, which could result in an increase of transients in the area. Study Strengths and Weaknesses Sighting effort for killer whales in the inside waters tends to be highest during summer and lowest during winter. It is therefore possible that the greater occurrences of transient killer whales during spring and summer, and the decrease of presence in winter months (November-March) could reflect reduced effort rather than lack of presence. However, based on cumulative numbers of individuals observed each month (Figure 2.4), whereby the number of individuals plateaus after approximately 75 occurrences (Figure 2.8), it appears that although the number of occurrences is low, the number of individuals may still be high. Thus, the significantly greater occurrences in summer months does not necessarily indicate that there were more individuals—as seen in Figure 2.4 where the number of individuals present increases in March and remains relatively high until September. Rather, the increased number of occurrences may be repeated 32 sightings of the same individuals in the area. Additionally, studies using hydrophones to detect transient killer whale presence in winter months in the northern Strait of Georgia have found transients present for approximately 42% of their 494 days across winter months from 2016-2018, which shows decreases in transient presence in winter months compared to their summer presence (Pilkington et al., 2023). It is suspected that transient presence in the winter decreases due to lower prey availability compared to summer months. Nevertheless, the number of occurrences in winter months should be considered a minimum estimate, yet it may not be as low as the data suggest due to reduced sighting effort. In contrast, transient killer whale occurrences and number of individuals present from April to October are considered extremely reliable due to the consistency with which whale watching companies are on the water through spring, summer and early fall. Therefore, during spring and summer, the number of occurrences and individuals present are considered accurate and are reflective of actual use of the area, rather than a minimum estimate. In terms of regional differences, sightings effort is lower in the North Island Waters compared to the Salish Sea. The Salish Sea has more whale watching companies, conservation organizations and killer whale research groups in the surrounding area that openly share their data. It is thus unlikely that individual transient killer whales would be missed while in the central and southern parts of the Salish Sea. Contrarily, for the North Island Waters, reported occurrences should be considered minimum estimates because there are fewer data sources and fewer whale watching companies to cover the entire area, even in summer months. Nevertheless, all indications are that transient killer whales make significantly greater use of the Salish Sea than the North Island Waters due in large part to the significantly higher densities of harbour seals in the Salish Sea (Majewski & Ellis, 2022). Thus, many of the sightings of transients in the North Island Waters may simply reflect this being their exit path from the Salish Sea as they proceed northward in their continued search for prey. Potential methods to strengthen data collection and results in the future would be to use additional sightings databases, particularly from the North Island Waters area. Additionally, other methods to monitor transient presence could be used such as hydrophones. However, it should not be the only method given that transient killer whales are less vocal than resident killer whales and may not be consistently heard on hydrophones. Transient killer whale vocalizations 33 are much less studied compared to resident killer whale vocalizations and the identification of individuals or matrigroups is not known for the transient population. Winter sightings could also be strengthened by using land-based sightings or boat transects throughout the year to estimate the abundance and density of transient killer whales in the inside waters of Vancouver Island. Conclusions Prior to this study, there was relatively little information concerning how transient killer whales use the inside waters of Vancouver Island, particularly the North Island Waters. The sightings data show that they are present year-round and that approximately 70% of the entire BC west coast transient killer whale population uses the area every year, which is significantly higher than anticipated. Given that the population ranges from California to southeast Alaska, it points to how important the inside waters of Vancouver Island are to the transient population. The reason why it appears to be so heavily used is most likely due to the high density of harbour seals and sea lions available for them to hunt. Whether the presence of transient killer whales in the inside waters, and the number of individuals that visit the area each year, will continue to increase, stabilize or decrease in the future will undoubtedly hinge on the ability of the inside waters to maintain healthy populations of pinnipeds and small cetaceans. Threats to the availability of their prey caused by disease (such as the avian flu) or culling could have significant negative consequences for the transient killer whale population and their important habitat. 34 Chapter 3: Differential Use of Shared Habitat by Two Ecotypes of Killer Whales in British Columbia Summary Two ecotypes of killer whales (Orcinus orca)—mammal-eating west-coast transient killer whales and fish-eating southern resident killer whales—are frequently observed in the Salish Sea (British Columbia and Washington State). This relatively small coastal area regularly draws over 60% of the west coast transient population, and all members of the southern resident population from waters as far south as California. However, the extent to which these two ecotypes co-occur seasonally in the Salish Sea, and whether their presence is driven by inter-related ecological factors has not been well evaluated. Comparing aerial, vessel and land-based sightings of killer whales in the Salish Sea from 2016-2022 showed that both killer whale ecotypes are often present all months of the year. However, transient killer whales used the Salish Sea more consistently, while southern resident presence varied by month and year on a pod level. Of the three southern resident killer whale pods, J pod was present the most often, with peak sightings occurring in March, July, September and November. In contrast, sightings of K and L pod were low until early summer and peaked in September. In terms of consecutive days of residency, southern residents were seen for a median of 4 days, and transients were seen for a median of 3 consecutive days. The southern residents generally travelled together at a pod level (median group size = 25), while the transient killer whales travelled with their matrigroups (median group size = 5). Both ecotypes of killer whales relied on the prey resources of the Salish Sea for more than 75% of the year—most notably on salmon for southern residents, and marine mammals for transients which are drawn in and sustained by herring and salmon. Effective conservation strategies should consider the distinct needs and ecological roles of both ecotypes to ensure their long-term survival and promote the overall health of the Salish Sea ecosystem. 35 Introduction The Salish Sea is a unique area in North America that spans the waters of British Columbia (BC) and Washington State (Figure 3.1). It provides habitat for a diversity of marine life including two ecotypes of killer whales (Orcinus orca): west coast transient killer whales (Bigg’s killer whales) and southern resident killer whales. West coast transient killer whales, henceforth referred to as transients, prey on marine mammals and range from southeast Alaska to central California (Ford et al., 2013; Ford & Ellis, 1999). While in BC waters, they primarily consume harbour seals (Phoca vitulina), Steller sea lions (Eumetopias jubatus) and harbour porpoise (Phocoena phocoena; Ford et al., 1998; Ford & Ellis, 1999). In contrast, southern resident killer whales prey on fish and primarily consume Chinook salmon (Oncorhynchus tshawytscha; Ford et al., 1998; Hanson et al., 2010). While southern residents also range as far south as central California, they have only been seen as far north as northern BC (Hanson et al., 2010; Krahn et al., 2004). Within their populations, transients tend to form matrigroups, consisting of a female killer whale, her undispersed offspring and other individuals known to travel with the group. However, there are also individuals who primarily travel on their own and may occasionally join up with matrigroups. These groupings frequently change, with different individuals interacting for varying amounts of time (Baird & Dill, 1995; Ford & Ellis, 1999). In contrast, resident killer whales are separated at a pod level, and the matrilines within each pod rarely separate (Bigg et al., 1990). Both populations—transients and southern residents—frequently overlap geographically within the Salish Sea, but rarely interact (Bigg, 1982). The Salish Sea is a relatively small, coastal area that includes the Strait of Georgia, Juan de Fuca Strait and Puget Sound. The area is home to thousands of marine species, including harbour seals, Steller sea lions, Chinook salmon, and Pacific herring (Clupea pallasii). Most Chinook salmon travel through the Salish Sea in spring, summer and early fall to enter the Fraser River and other spawning sites along the BC coast (Healey, 1983, 1991). Pacific herring also have a strong seasonal presence during spring when they return to spawn along the shores of the Salish Sea (Taylor, 1964). Both of these fish species are believed to draw marine mammals to the Salish Sea. Southern resident killer whales feed directly upon the Chinook salmon, while 36 transient killer whales prey upon other species of marine mammals that are drawn to seasonal abundance of salmon, herring, and other fin-fish species. This seasonal increase in prey species biomass may account in large part for the annual return of approximately 70% of the transient killer whale population (approximately 220 individuals; Chapter 2) and all southern residents (approximately 73; Center for Whale Research, 2022). The potential co-dependence of transient and southern resident killer whales on key fin-fish species, and the frequency with which they co-occur in the Salish Sea—and how their presence has changed over time—is poorly understood. Although named “residents” due to their frequent presence in the Salish Sea (Ford et al., 1998), southern resident killer whales have spent fewer days in the Salish Sea in recent years, possibly due to increased vessel disturbance, pollutants and a lack of prey, among other threats (Ford, Ellis, et al., 2010; Holt et al., 2021; Houghton, Holt, et al., 2015; Krahn et al., 2009; Lusseau et al., 2009; Stewart et al., 2021, 2023). In contrast, transient killer whales were rarely present in the Salish Sea prior to the early 2000’s (Baird & Dill, 1995; Ford & Ellis, 1999)—and are now seen year-round due most likely to recovery of harbour seals that were protected from hunting and culling in the 1970’s (Chapter 2). While the availability of food is thought to explain the presence of these two ecotypes of killer whales, little is known about their possible co-dependence on similar fish species. The aim of my research was to determine how transient killer whales and southern resident killer whales use the Salish Sea—and compare the similarities and differences between them relative to the seasonal presence of prey species. To do this, I collected sightings reports of transient and southern resident killer whales from 2016-2022 in the Salish Sea, and verified the identification of all individuals observed. I analyzed how often both populations were present, the seasonal variation in numbers at a population, pod and matrigroup level, and what may be driving these trends from a prey perspective. The findings highlight the importance of the Salish Sea for killer whales as a species, not just an individual population, and aids in the conservation of both transient and southern resident killer whales. 37 Methods Data collection and Study Area Transient and southern resident killer whales were tracked from 2016-2022 through a variety of sighting networks while in the Salish Sea—an area that includes the Strait of Georgia (50.25, -125.38), Puget Sound and the Strait of Juan de Fuca (48.50, -124.73) —and spans British Columbia and Washington State (Figure 3.1). Transient killer whale sightings were obtained from research, government and non-profit sources (as per Chapter 2), while southern resident killer whale sightings were compiled from open-access databases reported by Orca Network, the Center for Whale Research and Spy Hopper. Orca Network and Spy Hopper primarily collect sightings from the public, while the Center for Whale Research has researchers that track and report the presence of whales. Each sighting included the date and location (either geographic name or latitude and longitude). In addition, the Center for Whale Research also reported when and where the encounters began and ended, as well as identification of individuals and pods present. Individual transient killer whales typically travel within dynamic groups (matrigroups), and frequently disperse and travel with other individuals or matrigroups—while southern resident killer whales rarely disperse from their matriline, and often travel with their entire pod (i.e., all matrilines within a pod). Individuals within the southern resident killer whale population have an alphanumeric designation that begins with the letter of whichever pod they belong to (J, K or L) followed by the number in order of which they were identified in the population. In contrast, all members of the transient population have an alphanumeric designation—a ‘T’ followed by a number that represents the order in which they were identified. The only exception is for offspring who are given their mother’s ‘T’ designation, followed by a letter in order of which they were born. For example, T065A would be the first-born calf of the 65th individual identified (T065)—and the T065A’s would be a matrigroup led by this individual. Data Processing I only used sighting reports of southern resident killer whales from public databases that were supported with photos as per Chapter 2. The only exception was if the sighting report included a note indicating that the unphotographed identifications had been confirmed by Orca 38 Network staff, other researchers or industry professionals. All identifications of southern resident killer whales were verified using the Center for Whale Research catalogue (Center for Whale Research, 2019). I then added the matriline ID and IDs of all individuals encountered during the sighting, and the total number of whales present for the sighting was recorded as the “count”. Since southern resident killer whale matrilines rarely disperse, for the purposes of the count I assumed that all individuals in that matriline were present if only one individual within a matriline was photographed during the sighting. However, there were two exceptions. First, I only included J pod matrilines that were photographed for January-July 2016, and did not assume that other unphotographed J pod matrilines were present, because J pod matrilines were observed travelling separately during this period. Second, I considered L87 to be part of J pod from 2016-2020 when he travelled solely with J pod—and considered him part of L pod since 2020 when he returned to travelling with other L pod matrilines. Thus, I counted L87 as an individual, and not part of a matriline—and did not assume that other individuals were with him unless photographed. For sighting reports of transient killer whales from public databases, I only included the individuals photographed in my analysis (see Chapter 2). For all sightings of both ecotypes, I assumed that all identified individuals remained present throughout the entire sighting. 39 Figure 3.1 Map of the study areas. Panel A shows the larger study area, the Salish Sea, while panel B shows the sub-areas (Strait of Georgia, Puget Sound and Juan de Fuca Strait). 40 Many organizations have opted to not approach or specifically look for southern resident killer whales because of their endangered status. Thus, many whale watching companies do not track and observe southern residents, and may not report when they are present in the area. To account for this, I added assumed sightings to my database based on the last known location a pod was seen, time of last observation and direction of travel. I also added assumed sighting days when the southern residents had to have been in the Salish Sea, despite no reported sightings in that area. For example, if a southern resident killer whale matriline was observed travelling north in the Strait of Georgia on day 1, and was subsequently observed travelling south on day 3 in Puget Sound, I assumed that they had to have been in the Salish Sea on day 2. However, if southern residents last known location was westbound in the Juan de Fuca Strait, or at the northern end of the Strait of Georgia, assumed sightings were not added as the whales may have left the study area. I also assigned assumed sighting days based on sightings notes made by researchers. For example, if a confirmed sighting of a southern resident killer whale pod had a note such as “came down Haro Strait after four days at the Fraser River”, I included the four previous days as assumed sightings. For consistency, I also added assumed sightings to my transient killer whale database, following the same method used to determine southern resident killer whale assumed sightings. However, I only added assumed sightings for transient killer whale matrigroups that had been observed more than 20 times each year in the Salish Sea (Appendix A, Table A.2) because they showed a propensity for more regular and extended use of this habitat than other matrigroups. Assumed sightings were only included in the analyses of consecutive days present and percent of year present. To account for repeat sightings and varying levels of search effort, I separated all confirmed sightings of transient and southern resident killer whales into occurrences—defined as the presence of a unique group of killer whales that were not previously seen in a given day. For southern residents, a unique group could include a single pod or matriline, or multiple pods or matrilines. For transients, a unique group could be an individual matrigroup or a combination of individuals as defined in Chapter 2. If the same unique group was seen multiple times in one day, I retained the sighting with the highest number of identified individuals for analysis. 41 For each month, I counted the total number of days transient and southern resident killer whales were present in the Salish Sea to determine differences in use between the two populations. I also counted the total number of occurrences per month for all three southern resident killer whale pods (J, K and L) and transient killer whale matrigroups who were seen at least 20 times each year from 2016-2022 (Table A.2). For all of these groups I also counted the total number of consecutive days present in the Salish Sea (with assumed sightings included), and compared group sizes from all occurrences between the two ecotypes. To determine the importance of the area for both transients and southern residents, I compared the total number of days present in the Salish Sea per year for each population and both populations combined. Seasonal trends and differences in use between the two populations were noted. Data Analysis All data were analyzed using R (version 4.2.0) and R studio (version 1.3.1093). As the data were not normally distributed, non-parametric statistical analyses were used. To analyze the relationship between number of days present in the Salish Sea for transient killer whales, southern resident killer whales and both ecotypes combined, I used the Kruskal Wallis test with a post-hoc Dunn test with a Bonferroni correction to test for differences between months. I also used a Wilcoxon Rank Sum test with a Bonferroni correction to test for differences between the populations for each month. When looking at differences in use of the Salish Sea between pods and matrigroups, I used a Kruskal Wallis test with a post hoc Dunn test with Bonferroni correction. The total number of days per year individuals were present from each population were tallied and analyzed for each individual population and both ecotypes combined. Finally, I analyzed the relationship of total number of days present per year from 2016 to 2022 using a generalized linear model to test which interaction had the best fit, as well as whether the percent of year spent in the Salish Sea could be predicted based on year or ecotype. For consecutive number of days present and group size, I determined the mean, mode and range for each ecotype for all years combined (2016-2022). I then used the Wilcoxon Rank Sum test to determine whether differences in number of consecutive days present and group sizes between transient killer whales and southern resident killer whales were significant. 42 Results From 2016-2022, there were 4,317 occurrences of transient killer whales, and 879 occurrences of southern resident killer whales in the Salish Sea. While both ecotypes were present year-round, the overall presence of killer whales (1,955 days with at least one occurrence) in the Salish Sea was significantly higher during spring and summer (May-September) compared to winter (November-March) (Kruskal-Wallis c2 = 71.6, df = 11, p < 0.05; Figure 3.2; Appendix B, Table B.1). Transient killer whales were present on significantly more days per month than southern resident killer whales in the Salish Sea from April to September, with the exception of July, but their presence did not differ significantly from southern residents from October to March (W=1340.5 p < 0.001; Figure 3.2; Table B.2). Transient killer whales were consistently present from April to September, unlike southern residents that peaked in September and had varying levels of presence throughout the year (TKW: Kruskal-Wallis c2 = 60.742, df = 11, p < 0.01, SRKW: Kruskal-Wallis c2 = 40.634, df = 11, p < 0.01; Table B.3, Table B.4; Figure 3.2). 43 Table 3.1 Total number of occurrences (occur.), individuals and number of days present for both transient killer whales (TKW) and southern resident killer whales (SRKW) from 2016-2022. Mean and mode group size are also shown as well as the range in the number of individuals present during an occurrence. Note that 2021 and 2022 transient data is only from one data set and actual numbers may be higher. Total number of individuals seen and group size data are not included for transients in 2021 and 2022 since only one dataset was used during these years. Occur. Total # individuals seen (% of population) # days present (% of year present) Mean group size ± SE Mode group size Range of group size 2016 TKW 420 192 (60.76%) 206 (56.28%) 6.16 ± 0.22 4 1-26 SRKW 176 83 (100%) 230 (63.01%) 30 ± 1.21 30 5-82 2017 TKW 655 236 (71.52%) 229 (62.74%) 6.66 ± 0.18 4 1-31 SRKW 118 77 (100%) 178 (48.77%) 27 ± 1.03 25 2-62 2018 TKW 634 196 (56.00%) 236 (64.66%) 6.19 ± 0.15 4 1-24 SRKW 125 75 (100%) 173 (47.40%) 27 0.93 24 3-60 2019 TKW 766 215 (58.27%) 245 (67.12%) 6.60 ± 0.17 4 1-31 SRKW 121 73 (100%) 174 (47.67%) 26 0.92 23 2-73 2020 TKW 601 252 (68.67%) 241 (65.85%) 6.54 ± 0.16 4 1-27 SRKW 99 74 (100%) 143 (39.18%) 28 1.15 23 7-74 2021 TKW 579 - 240 (65.75%) - - - SRKW 92 74 (100%) 137 (37.53%) 28 1.26 24 4-62 2022 TKW 664 - 249 (68.22%) - - - SRKW 147 73 (100%) 211 (57.81%) 32 1.20 25 16-73 44 Figure 3.2 The total number of days transient and southern resident killer whales were observed in the Salish Sea from 2016-2022. The top panel represents the total number of days killer whales, both transient and southern resident combined, were present in the Salish Sea per month. The bottom panel shows the total number of days transient killer whales were present in the Salish Sea separated from the total number of days southern resident killer whales were present. Killer whales were present in the Salish Sea year-round; however, transient killer whales were present in the area more consistently than southern residents. Both panels were fit with a 33% span loess curve with a 95% confidence interval. The seasonal presence in the Salish Sea of the three pods (J, K and L) that make up the southern resident killer whale population differed significantly from one another (Figure 3.3; Kruskal-Wallis c2 = 62.344, df = 2, p < 0.001). In general, K and L pods appeared to make 45 similar use of the Salish Sea—with low presence from January-June, and notable peaks in presence during July, September and November (Figure 3.3). In contrast, J pod was present more frequently than either of the other pods throughout the year—but also showed similar peaks in occurrence to the others during July, September and November (along with an earlier peak in March; Figure 3.3; Table B.5). Overall, there was high variability in the month-to-month occurrences of each individual pod (J: Kruskal-Wallis c2 = 34.9, df = 11, p < 0.01, K: Kruskal-Wallis c2= 45.9, df = 11, p < 0.01, L: Kruskal Wallis c2 = 39.9, df = 11, p < 0.01), whereby post-hoc analysis confirmed that J and L pods occurrences were significantly higher in the Salish Sea during September compared to some spring months (February-June), while K pod had their highest occurrences in September, November and December compared to March, April and May (Table B.6). In terms of seasonal presence of the 6 matrigroups of transient killer whales that were seen more than 20 times each year in the Salish Sea, there were some similarities in their monthly presence (Figure 3.4). Most notable were lower levels of presence in the Salish Sea through winter months (October-March), and an increase in presence through spring and summer (April-August; Figure 3.4). However, peak occurrences varied significantly between matrigroups with some groups being primarily observed in the spring (T101’s, T123’s), while the presence of others peaked in late summer (T019’s, T065A’s, T100’s T137’s; Table B.7; Figure 3.4). Although there were significant differences between the six matrigroups in terms of their monthly use of the Salish Sea (p < 0.05; Table B.8), each matrigroup showed consistent seasonal use of the Salish Sea over the 5 years of study (Figure 3.4; Table B.8). The number of days that a matrigroup of transient killer whales (who were observed >20 times per year) stayed in the Salish Sea ranged from 1 to 42 days, and averaged 5 consecutive days and a median of 3 days (Figure 3.5). In comparison, southern resident killer whale pods were observed for an average of 6 consecutive days in the Salish Sea and a median of 4 days—with a range of 1 to 52 days of consecutive daily use. For both populations, the consecutive number of days counts includes assumed sightings of the population as described in the Methods. Overall, the number of consecutive days that a given group of killer whales were observed differed significantly between transients and southern residents (W = 75524, p < 0.01; Figure 3.5). 46 Figure 3.3 The total number of southern resident killer whale occurrences in the Salish sea per month, separated by pod from 2016-2022. The top panel shows total occurrences per month for J pod which peaks in March, July, September and November. The middle panel shows total occurrences per month for K pod which peaks in September. The bottom panel shows total occurrences per month for L pod which increases in July and peaks in September. All panels are fit with a 33% span loess curve with a 95% confidence interval. 47 Figure 3.4 The total number of transient killer whale occurrences per month in the Salish Sea for groups seen at least 20 times per year from 2016-2020. All panels were fit with a 33% span loess curve and have a 95% confidence interval. Presence between groups varied greatly with peaks occurring throughout the year. 48 Figure 3.5 Total number of consecutive days that transient and southern resident killer whale matrigroups or pods were observed in the Salish Sea. Note that the figure is truncated at 20 days, although southern resident killer whales were seen for >20 consecutive days on 7 occasions and transients were seen for >20 consecutive days on 11 occasions. Median number of consecutive days are shown with the dashed line in each panel. Transient killer whales were seen for median of 3 consecutive days, while southern resident killer whales were seen for a median number of 4 consecutive days. Number of consecutive days seen includes assumed sightings where it was assumed they were in that area on the days they were not sighted if a group was seen in the same area within 3 or fewer days. 49 Figure 3.6 The total number of transient and southern resident killer whales observed in groups ranging from 2 to 40 individuals in the Salish Sea. Median group sizes were 5 for transient killer whales and 25 for southern resident killer whales. Southern resident killer whale group size exceeded 40 individuals on 142 occasions, which are excluded from this graph, but were included in the analysis. Group sizes of transient killer whales present during each occurrence ranged from 1 to 31 individuals, with an average of 6 individuals and a mode of 4 individuals (Chapter 2; Figure 3.6). In comparison, southern resident killer whale group sizes ranged from 2-82 individuals, with an average of 28 individuals and a mode of 24 individuals present during each encounter (Figure 3.6). The difference between group sizes of southern resident and transient killer whales was significant (W = 3096110, p < 0.01). 50 Figure 3.7 The total percent of year that transient and southern resident killer whales spend in the Salish Sea. Percent of year present includes assumed sightings. Both populations of killer whales were fit with generalized linear models. Overall, killer whales, both transients and southern residents, were present in the Salish Sea more than 75% of the year. Overall, killer whales were present in the Salish Sea for more than 75% of the year (Figure 3.7). On average, transient killer whales used the Salish Sea for approximately 65% of each year (from 2016-2022), while southern resident killer whales were present for an average of 49% of the year (Figure 3.7). Year had no effect on the percent of year spent in the Salish Sea (based on generalized linear models fit to the data). However, ecotype as well as year and ecotype combined were significant (Table B.9). Discussion The results of my study demonstrate that the Salish Sea is an important habitat for killer whales. This relatively small inner coastal area regularly draws all members of the southern resident killer whale population (approximately 75 individuals) and over 60% of the BC west coast transient killer whale population (approximately 200 individuals) annually. Both ecotypes have been observed in the Salish Sea in all months of the year. However, transients tend to be present more frequently during spring and summer, while southern residents are primarily 51 present during late summer and early fall. There is evidence that some pods and matrigroups depend more than others on the Salish Sea to sustain themselves and that their dependence on the Salish Sea has changed significantly over past decades. Changing use of the Salish Sea Historically, the Salish Sea was where southern resident killer whales could be reliably found each summer, while transient killer whales were rarely seen. This is no longer the case. Transients were rarely seen in the 1980’s and 90’s, and are now in the Salish Sea year-round (Chapter 2). Previously, transients were observed in the Salish Sea for as long as 6 consecutive days (Houghton, Baird, et al., 2015), and are now staying for an average of 5 consecutive days, and have been seen spending as long as 42 consecutive days in the area. In comparison, the southern residents that historically appeared to reside in the Salish Sea during summer months (Bigg, 1982) have spent significantly less time in the Salish Sea over the last decade. They currently spend an average of 6 consecutive days in the inside waters, although they have stayed as long as 52 consecutive days. Overall, both ecotypes combined were present more than 75% of the year in the Salish Sea from 2016-2022, consistent with this being an important ecosystem needed to sustain them. While transients are spending more time in the Salish Sea and southern residents are spending less, it remains unclear why this decadal shift and difference in presence between the two ecotypes has occurred. One possibility is that the increasing numbers of transient killer whales is excluding or deterring southern residents from using the Salish Sea. However, the two ecotypes rarely interact, and there are few first-hand reports of antagonistic engagements. What limited information is available suggests that it is the residents that appear to target the transients, and that transients avoid areas where residents occur (Baird & Dill, 1995; Bigg, 1982; Morton, 1990). Given that each ecotype targets different prey species and the populations do not interbreed further suggests that it is unlikely that the presence of one ecotype should negatively affect the other. A more likely explanation for the shifts in presence may be responses to changes in prey availability. The presence of southern resident and transient killer whales in the Salish Sea parallels trends in the local availabilities of Chinook salmon and pinnipeds, respectively. For example, it 52 has been shown that the decline of Chinook salmon that has occurred through much of the northeast Pacific has had a greater impact on prey availability in the Salish Sea leading to a lower presence of the southern residents in summer months (May-October; Stewart et al., 2023). It can also be argued that southern residents are no longer expending the time and energy to enter the Salish Sea because they have found equally or more beneficial feeding areas elsewhere, such as Swiftsure Bank at the mouth of Juan de Fuca Strait or the Columbia River along the coast of Washington State and Oregon. Similarly, the increasing numbers of transients coming to the Salish Sea may be due to high densities of the smaller marine mammals that they target like harbour seals—or alternatively that carrying capacity constraints elsewhere in their hunting range have pushed them to seek out underexploited prey populations in the Salish Sea. Whatever the ultimate explanation might be, there is little doubt that there are seasonal limits on the ability of the Salish Sea to sustain the significant numbers of transients and southern residents that rely on it. Seasonality of Killer Whale Prey Killer whales have high energetic costs that can only be met by consuming energetically rich species such as Chinook salmon and harbour seals. This is consistent with both ecotypes occurring in greater numbers during seasons when lipid rich fish abundance increases (Figure 3.8). For example, the highest presence of transient killer whales from March-September occurs as pinniped concentrations serge in response to the availability of lipid rich fish such as Pacific herring and salmon (Edgell & Demarchi, 2012; Keple, 2002). Similarly, southern resident presence generally increased during late summer and into the fall as Chinook, chum and coho salmon returned to their natal rivers (Figure 3.8). Thus, the seasonal patterns in the presence of both ecotypes of killer whales from 2016-2022 is consistent with the seasonal availability of energy rich prey sources. 53 Figure 3.8 The number of days transient and southern resident killer whales were present each month from 2016-2022 relative to the major spawning times of Pacific herring, Chinook, coho and chum salmon. Spawning times are for the Salish Sea (primarily Fraser River stocks), although some of the species may be available in lower numbers at other times of year. In the Salish Sea, southern residents primarily prey upon returning Chinook salmon that spawn in greatest numbers from June-October in the Fraser River system (Hanson et al., 2010). The timing of their return corresponds with the increasing presence of southern residents that begins in June, and peaks in September when the highest numbers of Fraser River Chinook have arrived (Figure 3.8). In contrast, the later peak in November is consistent with high returns of chum and coho salmon. J and K pods have been documented consuming these less energetically dense salmon species in the Salish Sea in October, November and December (Hanson et al., 2021). A southern resident killer whale obtains an average of 13,409 kcal per chinook salmon consumed in September (O’Neill, Ylitalo, & West, 2014), and 4,265 kcal per chum and 4,982 kcal per coho in the months that follow (Hanson et al., 2021; O’Neill et al., 2014). Young adult Chinook salmon are also abundant in Puget Sound in late fall and make up a large portion of the southern resident diet, although they are not as energetically favourable as mature Chinook due to their smaller size and lower energetic density (Hanson et al., 2021; O’Neill et al., 2014). 54 In contrast to resident killer whales that require energy-dense fish, transients depend on energy-rich seals, sea lions and porpoise that themselves depend on energy-rich fish species, such as salmon and herring (Ford et al., 1998). Each spring (late-February, March and April), the spawning Pacific herring draws California and Steller sea lions to the Salish Sea (DFO, 2023; Keple, 2002; Olesiuk, 2018; Trites, 2014) which corresponds with the increased numbers of transients in March. In the months that follow (June – September), the large resident population of harbour seals gives birth, weans their pups and mate (Bigg, 1969) — all of which represent high value and predictable feeding opportunities for transient killer whales. As summer progresses to early fall, concentrated numbers of other marine mammals return to the Salish Sea to feed through to October on migrating salmonids (DFO, 2023; Keple, 2002; Trites, 2014). Thus, the Salish Sea supports a year-round population of seals that can reliably be accessed by a portion of the transient killer whale population year-round, but it is presumably the seasonal increases of returning herring in the spring and salmon in the fall that draws greater numbers of other small marine mammals from the outer waters of the Salish Sea needed to sustain the peak numbers of transients from March to October. Differential Use of the Salish Sea Although southern resident killer whales were seen on average in all months of the year (2016-2022), the three pods (J, K and L) did not make equal use of the Salish Sea. Of the three, J pod spent significantly more time in the Salish Sea than did K and L pods—as they have done previous decades. J pod historically used the Salish Sea year-round yet had the highest presence in summer months (May-August; Olson et al., 2018), but have more recently (2016-2022) reduced their peak occurrences to March, July, September and November, with little to no sightings during summer months in some years. Similarly, the presence of K and L pods used to begin increasing in June in the Salish Sea, and they would stay until January in some years (Olson et al., 2018). However, today, K and L pods are only relying heavily on the Salish Sea during September, and are making relatively little use of it at other times of year. K and L pods are often observed off the coast of Washington and Oregon from January–June, and occasionally in California, suggesting that prey availability is better during winter and spring in the southern portion of their range (Hanson et al., 2017). 55 Similar to the southern residents, there were also notable seasonal differences in how different matrigroups of transient killer whales used the Salish Sea. Of the matrigroups that used the Salish Sea the most (i.e., >20 times per year from 2016-2020), some preferred to come in spring, while others were mainly present during summer months. The seasonal differences between matrigroups suggests that some of them may specialize in hunting particular seasonally abundant prey species such as Steller or California sea lions in spring, or harbour seals in the summer. It is also notable that some matrigroups are present for the majority of the year, acting as a type of ‘resident’ transient killer whale—while other matrigroups are rarely seen and appear to be nomadic, travelling widely throughout their California to southeast Alaska range. Strengths and Weaknesses One of the primary limitations of killer whale presence and absence data in BC is that sightings effort is not constant throughout the year, particularly in winter months when conditions limit boats from being on the water, and the whale watching season stops. Thus, the fewer transient killer whales observed during winter months (November-February) could be due to a lack of effort rather than a lack of presence. If so, the calculated occurrences and number of days and individuals present should be considered minimum estimates (see Chapter 2). I partly mitigated for this possibility by adding assumed sightings when considering the number of consecutive days observed and percent of year present (this was also done for resident killer whale sightings). I also considered and compared patterns in the cumulative number of individuals observed each month with the number of occurrences (Chapter 2), and concluded that despite the reduced effort during winter the results are still sufficient to reflect number of transients present. Audio recording from moored hydrophones in the Strait of Georgia have also noted that fewer calls are made by transients during the winter compared to summer months, which is presumed to reflect relative differences in numbers of whales present (Pilkington et al., 2023). There was high confidence in the lower sightings in the winter months for southern residents as they spend the majority of their winter in Puget Sound, which has smaller waterways that make it easier to view and report whales from the shorelines. Thus, the conclusions about seasonal use of the Salish Sea by transient and southern resident killer whales appear sound despite uneven sightings effort. 56 I used different sightings databases for transient and resident sightings based on the availability of data. For example, Orca Network was the primary source used for southern residents because individual whales belonging to this ecotype generally require less expertise to identify than transients because their population is smaller, and their saddle patches are relatively easy to identify. In contrast, I relied more on private sightings databases with confirmed sightings of transient killer whales, as their population is significantly larger, and they are therefore harder to identify. Thus, I had high confidence in the quality of the data used in my analysis. In terms of movements, the swimming paths of southern resident killer whales are generally predictable because of the migrating salmon they follow, while movements of transients are more difficult to predict because of the wide distribution of harbour seals and sea lions in the Salish Sea. As a result, transient assumed sightings were more conservative. For example, if a matrigroup was not seen for two or more days, but was observed again days later in the same area, I could not conclude that they had been in that area the entire time as they may have briefly left and returned during the intervening days. Southern resident assumed sightings were easier to predict as they rarely travel north out the Strait of Georgia. Therefore, the number of consecutive days that transients are present may be higher than predicted. Occurrences (defined as unique groups of killer whales not previously seen on a given day) has been a commonly used metric to monitor and assess the abundance and distribution of killer whales from day to day (e.g. Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields, Hysong-Shimazu, Shields, & Woodruff, 2018). However, it has become an increasingly difficult metric to accurately determine for matrigroups as the number of consecutive days that transient killer whales have been spending in the Salish Sea has increased. While using the occurrence metric accounts for repeat sightings of the same group on consecutive days, it may overestimate use of the area due to inconsistencies in sightings effort. For example, although occurrences in summer are higher than early spring, this does not necessarily mean that more whales are present. Additionally, the fluidity of matrigroup structures (even within a day) can result in inflated occurrences if some matrigroups are counted multiple times. One way to reduce such sources of error, would be to rely more heavily on number of days that individuals are present, and to report the total number of individuals observed, rather than occurrences. 57 Another means to strengthen data collection and results would be to supplement sightings databases with other monitoring data sources. For example, hydrophones that detect killer whale presence could also be incorporated into future analyses of habitat use, particularly for southern residents as each pod has a distinct dialect (Ford & Fisher, 1983). However, identification can only be done to the pod level and not the individual as it is not yet possible to identify individual whale vocalizations. Consideration should also be given to standardizing effort to account for months with fewer boats on the water. Similarly, boat transects that encompass all of the Salish Sea could be completed to better assess abundance and distribution of southern resident and transient killer whales at different times of year. Conclusions Most research has examined southern resident and transient killer whales independently, and has not considered how both ecotypes simultaneously use the Salish Sea — nor the extent to which key fish species drives their joint presence in the area. Based on seasonal peaks in numbers of transient killer whales, the high numbers of spawning herring that return to the inside waters each spring appear to draw large concentrations of sea lions that in turn supports the increase of transient individuals. Similarly, the continued presence of high numbers of transients through the summer months appear to be supported by births and high densities of harbour seals during pupping—while fall concentrations of transients are likely supported by pinnipeds and small cetaceans that have been drawn to the return of spawning salmon. Similarly, the annual return of spawning Chinook, coho and chum in the late summer and early fall is an equally dependable and predictable food source to support southern resident killer whales. Such seasonally high densities of concentrated prey sought by transient and southern resident killer whales can account for why such a high proportion of both ecotypes use the Salish Sea, and why they come here for more than 75% of the year. Thus, the extent to which the Salish Sea will continue to support high numbers of killer whales will likely depend on the continued presence of lipid rich prey. Maintaining killer whale prey species populations and accessibility to them should be a high conservation priority to sustain the health of both transient and southern resident killer whale populations in the Salish Sea. 58 Chapter 4: General Discussion Summary of Findings Killer whales have always been an important part of the Salish Sea ecosystem. However, both west coast transient killer whales (transients) and southern resident killer whales use of the area has changed in recent years. While transient killer whale presence in the area has increased, sightings of southern residents have declined. The reasons for these changes are unknown but are generally believed to be due in large part to prey availability. Baseline data for how the two populations use the Salish Sea and other coastal regions of British Columbia has been missing. This led me to my overarching research question of “how important are inside waters of Vancouver Island (North Island Waters and the Salish Sea) to killer whale populations?”. Using sighting reports of transient killer whales and southern resident killer whales, I analyzed transient killer whale abundance and distribution in the inside waters of Vancouver Island (Chapter 2). I then compared how the two ecotypes use the Salish Sea in particular and evaluated what may be driving their movement patterns (Chapter 3). Overall, I found that a large percentage of both transients (71% of population) and southern residents (100% of population) use the inside waters of Vancouver Island each year, with new transient killer whales being observed in the area each year. Seasonally, I found that transients are present in the area year-round, but that the greatest numbers of individuals are consistently present from March-October. Contrarily, southern resident killer whale presence varies throughout the year and peaks in late summer and fall months (September-November). However, during some months in the study years (2016-2022), there were no southern resident killer whale sightings. The presence of both ecotypes in the inside waters appears to be driven by key fish species such as Pacific herring and Chinook salmon as either the killer whales themselves, or their prey, rely on these fish. This is especially apparent for transient killer whales as they have an even vs. odd year pattern every July where in even years their presence in the Salish Sea decreases significantly, which I hypothesize is related to the pink salmon spawn which occurs in the Salish Sea in odd years (high transient presence) and in northern BC and Alaska in even 59 years (low transient presence). This is the first study to identify this pattern in transient killer whales. Killer whales continue to be an important part of the Salish Sea ecosystem as their use of the area is increasing. While southern residents are not seen as often, nor in the same months as they used to be, transient killer whales’ presence, and the number of individuals visiting the area, continues to increase, most likely due to the year-round availability of harbour seals, Steller sea lions and California sea lions. Project Strengths and Weaknesses One of the main strengths of my project is the number of transient killer whale sightings I had in my dataset. Since I was able to collect sightings from multiple datasets, I had a total of 35,467 transient killer whale sightings of one or more individuals from 2016-2023, which resulted in 5,703 occurrences. Since there were such a large number of sightings, the results of transient killer whale abundance and distribution are highly reliable, particularly for summer months, since sightings were collected from many individuals and organizations who were on the water every day. While there were fewer sightings of southern resident killer whales, I added assumed sightings to mitigate for missing sightings on days they were in the area, but were not observed. This increased the total number of sightings of the population, and was justifiable because the movement patterns of southern residents that follow migrating salmon pathways are easy to predict (as discussed in Chapter 3). While there were many transient killer whale occurrences, sightings from the North Island Waters and winter months were lacking. The North Island Waters is a much less populated area compared to the Salish Sea and has more uninhabited inlets that killer whales can travel up without being observed. While sightings increase through summer months in the North Island Waters during the commercial whale watching season, the smaller number of companies in the north (~13) compared to those in the Salish Sea (>35) may result in killer whales being missed. Additionally, many of the companies in the North Island Waters are not part of the Pacific Whale Watching Association, so I was unable to access their sightings databases. There are also fewer sightings during winter months because the whale watching season runs from March-October. However, transient killer whale presence in the area most likely decreases 60 during winter due to a decrease in prey abundance and availability. Therefore, due to these limitations, results from the North Island Waters and during winter months should be considered minimum estimates. I designed my study following previous research on transient killer whales in the Salish Sea (Baird & Dill, 1995; Houghton, Baird, et al., 2015; Shields et al., 2018), which all used occurrences to mitigate the issue of effort level and to account for repeat sightings of whales. However, I found that using occurrences was not the best way to analyze transient killer whale presence because the number of individuals being observed plateaus after a certain number of occurrences per month (Chapter 2). This means that subsequent sightings tend to be of the same group seen multiple days in a row. This shows that even in winter months when occurrences are low, there can still be a high number of individuals present. Using occurrences as a measurement seems to inflate the apparent number of whales in the area. Although the seasonal patterns are correct, numbers of occurrences tend to be extremely high because multiple groups are seen several days in a row. Additionally, since an occurrence was defined as a unique group of killer whales, if there were two sightings of the same group travelling with other whales who had not yet been observed in that day, both sightings would be included in the occurrences which results in some groups being included in multiple occurrences in one day. While this increases the total number of occurrences, it does not affect the total number of individuals observed. Future studies of transient killer whales should use number of individuals or number of days per month individuals were observed to analyze killer whale abundance. Alternatively, if occurrences are used, they should be weighted based on the number of vessels reporting sightings. This does not necessarily apply to southern resident killer whales that primarily only travel with their pods, which reduces the risk of the same individuals being identified multiple times in one day. Thus, number of occurrences can be used to measure southern residents use of an area, as well as spatial and seasonal patterns. Future Research The results of my research show the importance of the Salish Sea for both transient and southern resident killer whale populations. More effort is needed to collect transient killer whale 61 sighting reports in the North Island Waters to determine their actual use and the importance of the area as it is currently unclear if the area is used for foraging, or, if it is mainly used as a pathway to and from the Salish Sea. This can be done by connecting with whale watching companies and research organizations to obtain their data for future studies, particularly with organizations who have land-based sightings or access to aerial sightings for year-round data. To address the effort level issue, more research needs to be conducted and sightings need to be collected in winter months. Since ocean conditions generally prevent vessels from searching for whales in winter months, more land-based sightings need to be collected, which is difficult in the central Strait of Georgia. Alternatively, line transects could be done on a large vessel that is not susceptible to bad weather conditions, such as ferries, to evaluate transient killer whale presence. Underwater hydrophones could also be used to determine killer whale presence; however, identifications could only be identified to a pod (southern resident killer whale) or ecotype (transient killer whale) level. This was the first study to identify an alternating year pattern (odd vs. even years) of transient killer whale presence in July. While it remains unknown why this pattern occurs, my best guess is that it is related to the pink salmon spawn and future work should be completed analyzing the effect that important fish species, such as pink and Chinook salmon and Pacific herring, have on killer whale populations. Furthermore, while the southern resident killer whale diet has been well studied (Ford et al., 1998; Ford, Wright, et al., 2010; Ford et al., 2016; Hanson et al., 2010, 2021; Warlick et al., 2020) and Chinook salmon has been identified as the primary prey item for the population, less is known about the diets of transients, especially those that frequent the inside waters of Vancouver Island. In addition to learning more about the diets of transient killer whales, a bioenergetics model for the population should be completed to determine how reliant transient killer whales are on the local harbour seal and sea lion populations. Future research should consider my findings as a baseline of how transient and southern resident killer whale use the inside waters of Vancouver Island. This can contribute to evaluating critical habitat in BC for both ecotypes, and for considering regulations that may be needed to protect the populations. Varying use of the inside waters by both ecotypes points to the need for 62 more research into the importance of other key feeding areas throughout the range of transient and southern resident killer whales. Conclusions Overall, my analyses have provided valuable insights into the shifting dynamics of transient killer whales and southern resident killer whales in the inside waters of Vancouver Island. My findings emphasize the vital role that key fish species have on the seasonal abundance of both killer whale ecotypes, highlighting the interconnectedness of the Salish Sea ecosystem and how dependent both populations are on healthy and abundant prey. As killer whales continue to play a crucial role in the inside waters of Vancouver Island, my findings provide a foundation for conservation and management strategies to ensure the long-term health and sustainability of west coast transient killer whales, southern resident killer whales and their important habitat. 63 References Baird, R. 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McFarlane (Eds.), The Sea Among Us: The Amazing Strait of Georgia (pp. 183–210). Harbour Publishing Co. Warlick, A. J., Ylitalo, G. M., O’Neill, S. M., Hanson, M. B., Emmons, C. K., & Ward, E. J. (2020). Using Bayesian stable isotope mixing models and generalized additive models to resolve diet changes for fish-eating killer whales Orcinus orca. Marine Ecology Progress Series, 649, 189–200. https://doi.org/10.3354/meps13452 74 Appendices Appendix A Supporting tables for Chapter 2 Table A.1 Individual transient killer whales with a ‘T’ designation that were observed in the inside waters of Vancouver Island between 2016 and 2022 that were not in the published catalogue of west coast transient killer whales (Towers et al., 2019), but are recognized by DFO as being members of the population. Note that 2021 and 2022 is limited to one dataset and other individuals with a ‘T’ designation that are not in the catalogue may also have been in the area. 2016 2017 2018 2019 2020 2021 2022 T196 T221B T234 T256 T233 T237 - T197 T234 T234A T259 T233A T234A T235 T261 T235 T236 T261A T236 T240 T261B T237 T241 T249 T291 T249A T292 T249B T308 T308 75 Table A.2 Matrigroups and solitary individual transient killer whales observed more than twenty times in either the North Island waters or Salish Sea from 2016-2020 in summer months (May-September). Only summer months were used as sighting effort during this time is the highest and it is unlikely for a group to be missed. Note that the T090’s in 2019 were the only group seen more than 20 times in the North Island Waters. 2016 2017 2018 2019 2020 T002C’s T002C’s T002C’s T002C’s T018’s T036A’s T018’s T018’s T018’s T037A’s T065A’s T034’s T034’s T034’s T046’s T100’s T036A’s T036A’s T036A’s T046B’s T123’s T036B’s T037A’s T036B’s T060’s T124A’s T037A’s T037B’s T037A’s T065A’s T137’s T037B’s T049A’s T037B’s T065B’s T046’s T065A’s T046’s T101’s T046B’s T090’s T046B’s T123’s T065A’s T099’s T049A’s T137’s T099’s T100’s T065A’s T101’s T101’s T065B’s T137’s T124A’s T086A1 T137’s T090’s T099’s T101’s T123’s T124A’s T124A1 T124A2’s T124C T137’s 76 Table A.3 P-values from Wilcoxon rank sum test testing if there was a significant difference in the number of transient killer whale occurrences per year between the North Island Waters (NIW) and the Salish Sea (SS). Overall, there was a significant difference between number of occurrences in both areas for all years (2016-2020). Year NIW Occurrences SS Occurrences p-value 2016 99 420 0.0039 2017 87 655 0.0026 2018 109 634 0.0016 2019 133 766 0.014 2020 136 601 0.0018 77 Table A.4 Post-hoc pairwise comparisons of number of occurrences between study years (2016-2020) in the North Island Waters and the Salish Sea with Z scores, unadjusted p-values and adjusted p-values. There was no significant difference in the number of transient killer whale occurrences per year, from 2016-2020 in either area. Year comparison Z score Unadjusted p-value Adjusted p-value North Island Waters 2016-2017 0.42 0.68 1 2016-2018 -0.50 0.62 1 2017-2018 -0.92 0.36 1 2016-2019 -1.11 0.27 1 2017-2019 -1.52 0.13 1 2018-2019 -0.60 0.55 1 2016-2020 -0.94 0.35 1 2017-2020 -1.36 0.17 1 2018-2020 -0.44 0.66 1 2019-2020 0.16 0.87 1 Salish Sea 2016-2017 -0.81 0.42 1 2016-2018 -0.96 0.34 1 2017-2018 -0.15 0.88 1 2016-2019 -1.15 0.25 1 2017-2019 -0.35 0.73 1 2018-2019 -0.19 0.85 1 2016-2020 -0.88 0.37 1 2017-2020 -0.08 0.94 1 2018-2020 0.08 0.94 1 2019-2020 0.27 0.79 1 78 Table A.5 Statistical test results (p-values and level of significance) assessing whether there was a significant difference in the number of transient killer whale occurrences per month between the North Island Waters and the Salish Sea. The two areas differed in all months except December. Month p-value Significance (* <0.05, ** <0.01) January 0.021 * February 0.020 * March 0.0079 ** April 0.0079 ** May 0.012 * June 0.0079 ** July 0.012 * August 0.0079 ** September 0.0079 ** October 0.012 * November 0.012 * December 0.20 ns 79 Table A.6 Z scores, unadjusted p-values and adjusted p-values for monthly pairings that had a significant difference in the number of occurrences of transient killer whales per month in the North Island Waters and the Salish Sea. All month comparisons not shown had adjusted p-values that were not significant (p > 0.05). Month Comparison Z score Unadjusted p-value Adjusted p-value North Island Waters January-September -4.14 0.000035 0.0023 February-September -3.86 0.00011 0.0074 November-September -3.89 0.00010 0.0066 December-September -3.77 0.00017 0.0074 Salish Sea January-June -3.90 0.000099 0.0075 December-June -3.58 0.00035 0.023 January-July -3.61 0.00030 0.020 January-August -4.37 0.000012 0.00081 February-August -3.79 0.00015 0.010 November-August -3.45 0.00056 0.037 December-August -4.06 0.000050 0.0033 January-September -3.82 0.00013 0.0087 December-September -3.51 0.00046 0.030 80 Table A.7 Monthly comparisons with significant values (p < 0.05) of transient killer whale group size in the Salish Sea. All monthly comparisons not shown did not have a significant adjusted p-value (p > 0.05). Month Comparison Z score Unadjusted p-value Adjusted p-value March-June -3.44 0.00058 0.038 November-June -3.66 0.00031 0.021 March-July -4.32 -0.000016 0.0011 October-July -3.45 0.00057 0.037 November-July -4.28 0.000019 0.0013 June-September 3.39 0.00070 0.047 July-September 4.64 0.0000035 0.00023 81 Table A.8 W statistics, unadjusted p-values and adjusted p-values of yearly comparisons of group size of transient killer whales between the North Island Waters and the Salish Sea. P-values were adjusted using the Bonferroni method. Year W statistic Unadjusted p-value Adjusted p-value 2016 17228 0.0071 0.035 2017 21752 0.00029 0.0015 2018 26292 0.000055 0.00028 2019 44576 0.0186 0.093 2020 34806 0.0063 0.031 82 Table A.9 Wilcoxon rank sum test results for testing if there is a significant difference in transient killer whale group size per month between the North Island Waters and the Salish Sea. P-values were adjusted using the Bonferroni method. Month W statistic Unadjusted p-value Adjusted p-value January 129 0.017 0.20 February 336 0.091 1.00 March 2415 0.81 1.00 April 4060 0.81 1.00 May 8630 0.42 1.00 June 11290 0.0010 0.012 July 10448 0.019 0.23 August 17960 0.00085 0.010 September 22872 0.00056 0.0067 October 3260 0.0029 0.035 November 699 0.54 1.00 December 461 0.84 1.00 83 Table A.10 Transient killer whale matrigroups and individuals observed in the same year in both the North Island Waters and the Salish Sea from 2016-2020. Note that in 2018, T002B had an offspring and was considered a matrigroup, however for all other years T002B was considered an individual. Matrigroups Individuals T002Bs T100s T002B T002Cs T100Bs T037A1 T010s T101s T046C2 T011s T109s T049A2 T018s T019As T049C T023s T117s T051 T023Cs T123s T068B T028s T124As T068B3 T030s T124A2s T068B4 T030Bs T124Ds T073B T034s T137s T077A T035As T167s T086A1 T036s T087 T036As T117A T037s T124A1 T037As T124C T041s T124E T046s T125A T046Bs T128 T049As T146 T049Bs T146B T050s T170 T059s T172 T060s T065s T065As T065Bs T068s T069s T069As T069Ds T073As T075s T075Bs T075Cs T077s T086As T090s T099s 84 Table A.11 Monthly comparisons of transient killer whale group size between the North Island Waters and the Salish Sea with Z scores, unadjusted p-values and adjusted p-values. All monthly comparisons not shown were not significant (p > 0.05). Month Comparison Z score Unadjusted p-value Adjusted p-value January-June -3.53 0.00041 0.027 January-August 3.62 0.00029 0.019 January-September -4.14 0.000035 0.0023 February-September -3.80 0.00014 0.0094 December-September -3.70 0.00021 0.014 85 Table A.12 List of matrigroups and lone individuals who were observed every year from 2016-2020 in the inside waters of Vancouver Island. Matrigroups Individuals T002Cs T002B T010s T037A1 T011s T049C T018s T059A T023s T059A2 T023Cs T059A3 T030s T075C T034s T077 T035As T077A T036s T077C T036As T077D T037s T077E T037As T086A1 T038s T087 T038As T093 T041s T097 T046s T124A1 T046Bs T124C T046Cs T125A T049As T128 T049Bs T055s T060s T065s T065As T065Bs T069s T069As T073As T075s T075Bs T086As T090s T099s T100s T100Bs T101s T109As T123s T124As T124A2s T124Ds T137s 86 Table A.13 Total number of matrigroups and lone individuals who were not observed in the inside waters of Vancouver Island in the previous year from 2017-2020. Number of matrigroups not observed previous year Number of lone individuals not observed previous year 2017 8 8 2018 8 4 2019 7 10 2020 5 8 87 Table A.14 Outputs from a generalized linear model testing if the trend in the percent of transient killer whale population present from 2016-2020 in the North Island Waters, the Salish Sea and both areas combined was significant. Model AIC Coefficients Estimate Standard Error t-value p-value Model 1 (proportion of population ~ year) -10.85 Intercept -18 53 -0.34 0.74 Year 0.0091 0.026 0.35 0.74 Model 2 (proportion of population ~ year + area) -19.80 Intercept -18 33 -0.55 0.60 Year 0.0091 0.016 0.57 0.59 AreaSS 0.17 0.050 3.73 0.0074 Model 3 (proportion of population ~ year*area) -18.04 Intercept -31 49 -0.64 0.55 Year 0.016 0.024 0.65 0.54 AreaSS 27 69 0.39 0.71 Year:AreaSS -0.013 0.034 -0.38 0.72 88 Table A.15 Outputs from generalized additive model testing the relationship between number of individuals present per month and number of occurrences per month. The relationship was significant. Model AIC Coefficient Estimate Standard Error t-value p-value Individuals ~ s(occurrences) 675 Intercept 74 1.4 53 2.0 x 10-16 89 Appendix B Supporting tables for Chapter 3 Table B.1 Monthly comparisons to determine which pairings are significantly different in the number of confirmed killer whale days. All monthly comparisons not shown had adjusted p-values that were not significant (p > 0.05). Significance was tested using Kruskal Wallis test with post hoc Dunn test with Bonferroni correction. P values less than 0.0001 are shown as < 0.0001. Monthly Comparison Z score Unadjusted p-value Adjusted p-value January-May -3.80 0.00015 0.0097 January-June -3.82 0.0003 0.0089 January-July -5.26 < 0.0001 < 0.0001 January-August -5.00 < 0.0001 < 0.0001 January-September -4.32 < 0.0001 0.0016 February-May -3.75 0.00025 0.016 February-June -3.77 0.00018 0.011 February-July -5.22 < 0.0001 < 0.0001 February-August -4.96 < 0.0001 < 0.0001 February-September -4.18 < 0.0001 0.0020 March-July -3.47 0.00052 0.034 November-July -3.71 0.00021 0.014 November-August -3.45 0.00056 0.037 December-July -4.20 < 0.0001 0.0017 December-August -3.94 < 0.0001 0.0054 90 Table B.2 Results for Wilcoxon Rank Sum test for difference in number of days present per month between transient killer whales and southern resident killer whales. All months were significant with the exception of January and December. P-values were adjusted post-hoc using the Bonferroni method. Month W statistic Unadjusted p-value Adjusted p-value January 29 0.28 1.00 February 6 0.031 0.37 March 3 0.0099 0.12 April 0 0.0029 0.035 May 0 0.0032 0.038 June 0 0.0032 0.040 July 1 0.0053 0.063 August 0 0.0032 0.038 September 0 0.0032 0.039 October 3 0.0123 0.15 November 36 0.045 0.54 December 35 0.052 0.62 91 Table B.3 Results of monthly comparisons of number of days transient killer whales were present per month. Significance was tested using a Kruskal-Wallis test followed by a post hoc Dunn test with a Bonferroni correction. All monthly comparisons not listed had adjusted p-values that were not significant. P values less than 0.0001 are shown as < 0.0001. Monthly Comparison Z Score Unadjusted p-value Adjusted p-value January-May -3.68 0.00024 0.016 January-June -3.83 0.00013 0.0083 January-July -4.02 < 0.0001 0.0038 January-August -4.70 < 0.0001 0.00017 January-September -3.76 0.00017 0.011 February-July -3.50 0.00046 0.031 February-August -4.18 < 0.0001 0.0019 November-August -3.61 0.00030 0.020 December-May -3.58 0.00035 0.023 December-June -3.74 0.00019 0.012 December-July -3.92 < 0.0001 0.0058 December-August -4.60 < 0.0001 0.00028 December-September -3.66 0.00025 0.017 92 Table B.4 Results of monthly comparisons of number of days southern resident killer whales were present per month. Significance was tested using a Kruskal-Wallis test followed by a post hoc Dunn test with a Bonferroni correction. All monthly comparisons not listed had adjusted p-values that were not significant. P values less than 0.0001 are shown as < 0.0001. Monthly Comparison Z score Unadjusted p-value Adjusted p-value September-February -3.99 < 0.0001 0.0044 September-April -3.54 0.00040 0.026 September-May -4.39 < 0.0001 0.00074 September-June -3.44 0.00059 0.039 November-February 3.48 0.00050 0.033 November-May 3.88 0.00010 0.0069 93 Table B.5 Results from Kruskal-Wallis test for each month testing if there was a difference in the number of occurrences per month between the three pods (J,K,L). Only months with significant differences are shown, all other months had p-values greater than 0.05. Note that January also was significant when testing if there was a significant difference in the number of occurrences per month between pods (Kruskal-Wallis c2 = 6.2, df = 2, p-value = 0.04505). However, when completing the post hoc Dunn test it was found that of the direct comparisons (J-K, J-L, K-L), none were significant, so it was excluded from the table. P values less than 0.0001 are shown as < 0.0001. Month Kruskal-Wallis c2 Df p-value Pod Comparison Z score Unadjusted p-value Adjusted p-value February 10.50 2 0.0052 J-K 2.71 0.0067 0.020 J-L 2.89 0.0038 0.012 K-L 0.18 0.86 1.0 March 16.43 2 0.00027 J-K 3.49 0.00049 0.0015 J-L 3.53 0.00041 0.0012 K-L 0.05 0.96 1.0 April 19.14 2 < 0.0001 J-K 3.79 0.00015 0.00045 J-L 3.79 0.00015 0.00045 K-L 0.00 1.0 1.0 October 11.85 2 0.0027 J-K 2.93 0.0034 0.010 J-L 3.03 0.0024 0.0072 K-L 0.11 0.91 0.90 November 8.78 2 0.012 J-K 1.88 0.060 0.18 J-L 2.02 0.035 0.010 K-L 1.04 0.30 0.90 December 13.87 2 0.0097 J-K 1.53 0.13 0.38 J-L 3.71 0.00021 0.00064 K-L 2.18 0.029 0.088 94 Table B.6 Results from testing if there was a significant difference in the number of occurrences per month between each individual matrigroup. Monthly comparisons that had adjusted p values that were not significant were not included in this table. P values less than 0.0001 are shown as < 0.0001. Pod Monthly Comparison Z score Unadjusted p value Adjusted p value J pod February-September -3.85 0.00017 0.0077 May-September -3.96 < 0.0001 0.0049 June-September -3.44 0.00062 0.041 K pod March-September -3.85 0.00012 0.0080 April-September -4.19 < 0.0001 0.0018 May-September -3.94 < 0.0001 0.0053 November-March 3.45 0.00055 0.036 November-April 3.80 0.00014 0.0094 November-May 3.55 0.00038 0.025 December-March 3.44 0.00059 0.039 December-April 3.79 0.00015 0.010 December-May 3.54 0.00041 0.027 L pod February-September -3.65 0.00026 0.017 March-September -4.34 < 0.0001 0.0010 April-September -4.60 < 0.0001 0.00028 May-September -4.34 < 0.0001 0.00096 95 Table B.7 Results of the Kruskal Wallis test with post hoc Dunn test testing if there were significant differences in the number of occurrences per month between matrigroups observed more than twenty times each year from 2016-2022. Only months and matrigroup comparisons that had significant p-values (p < 0.05) are shown. All other months and matrigroup comparisons had adjusted p-values greater than 0.05. Note that November also tested as having a significant difference in the number of occurrences between matrigroups, however, the post hoc Dunn test produced no matrigroup comparisons that had adjusted p values that were significant therefore November was not included in the table. P values less than 0.0001 are shown as < 0.0001. Month Kruskal Wallis c2 Df p-value Matrigroup Comparison Z score Unadjusted p-value Adjusted p-value February 13.55 5 0.019 T065As-T101s -3.17 0.00016 0.023 April 12.69 5 0.027 T065As- T137s 3.20 0.0014 0.021 May 13.72 5 0.018 T123s- T137s 2.94 0.0033 0.049 June 12.12 5 0.033 T019s-T065As -3.31 0.00095 0.014 July 14.75 5 0.012 T019s-T065As -2.87 0.0041 0.062 T100s-T065As 3.13 0.0018 0.027 August 16.41 5 0.0058 T065As-T123s 3.77 0.00016 0.0024 96 Table B.8 Test results for the significance of the number of occurrences per month within each matrigroup observed twenty or more times each year within the study period. All monthly comparisons not shown for each matrigroup had an adjusted p value greater that 0.05. P values less than 0.0001 are shown as < 0.0001. Matrigroup Kruskal-Wallis Df p-value Monthly Comparison Z score Unadjusted p-value Adjusted p-value T019s 41.96 11 < 0.0001 January-August -3.97 < 0.0001 0.0028 January-September -3.91 < 0.0001 0.0060 June-August -3.66 0.00025 0.017 June-September -3.60 0.00032 0.021 November-August -3.66 0.00025 0.017 November- September -3.60 0.00032 0.021 T065As 42.80 11 < 0.0001 January-August -3.54 0.00041 0.027 February-August -3.81 0.00014 0.0093 November-August -3.45 0.00056 0.037 December-August -3.40 0.00069 0.045 T100s 24.92 11 0.0094 November-September -3.44 0.00058 0.038 December-September -3.44 0.00058 0.038 T101s 32.98 11 0.00053 December-May -3.89 0.00010 0.0066 December-June -3.60 0.00032 0.021 T123s 38.43 11 < 0.0001 January-May -3.66 0.00025 0.016 February-May -3.66 0.00025 0.016 August-May 3.53 0.00041 0.027 December-May -3.53 0.00041 0.027 T137s 25.33 11 0.0082 January-August -3.77 0.00017 0.011 February-August -3.377 0.00074 0.049 97 Table B.9 Generalized model results testing the percent of year transient killer whales and southern resident killer whales spend in the Salish Sea from 2016-2022. P values less than 0.0001 are shown as < 0.0001. Model AIC Coefficients Estimate Standard Error t-value p-value Model 1 (percent of year present ~ year) -18.21 Intercept 1.6 28 0.054 0.96 Year -0.00051 0.015 -0.035 0.97 Model 2 (percent of year present ~ year + ecotype) -28.66 Intercept 1.5 20 0.077 0.94 Year -0.00051 0.0099 -0.052 0.96 Ecotype (TKW) 0.16 0.039 4.0 0.0022 Model 3 (percent of year present ~ year*ecotype) -30.44 Intercept 34 26 1.3 0.22 Year -0.016 0.013 -1.3 0.23 Ecotype (TKW) -64 37 -1.8 0.11 Year:Ecotype (TKW) 0.032 0.018 1.8 0.11
Thesis/Dissertation
eng
Zoology
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Graduate
Trites, Andrew W., 1957-
Killer whale use of the inside waters of Vancouver Island, British Columbia
Text