Open Collections

Scarff, Taryn M.

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.

Text

2025-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87724

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/