Sightings of southern resident killer whales in the Salish Sea 1976−2014: the importance of a long-term opportunistic dataset

A 2018 paper in the journal Endangered Species Research analyzes southern resident killer whale sightings in the Salish Sea between 1976 and 2014. 

Southern resident killer whale breaching. Image courtesy of NOAA
Southern resident killer whale breaching. Image courtesy of NOAA

A recently published manuscript by scientists at the Whale Museum in Friday Harbor shows how more than 40 years of opportunistic sightings were used to look at habitat use and establish baseline patterns of endangered Southern Resident Killer Whales. Effort corrected data were used to highlight a few key ‘hot spots’ in the Salish Sea and to establish an overall pattern of consistent presence in the Central Salish Sea during the summer months and a presence in Puget Sound proper during the fall and early winter months. A surprising shift in SRKW presence in Puget Sound documented in the late nineties supports the hypothesis that the movement patterns of these whales may be driven by prey availability and highlights the importance of long-term monitoring.

Abstract

Southern resident killer whales (SRKWs) Orcinus orca may be present year round in the Salish Sea, i.e. the inland waterways of Washington State (USA) and southern British Columbia (Canada). SRKWs were listed as endangered in 2005 under the US Endangered Species Act. The Whale Museum (Washington, USA) has been collecting opportunistic sightings reports on SRKWs since 1976 with a goal of providing managers and regulatory agencies with reliable spatial and temporal data on this population. Information in this dataset comes from 5 classes of killer whale sighting sources and is systematically evaluated for accuracy before integration into the dataset. From 1976 to 2014, The Whale Museum’s Orca Master dataset documented a total of 82 447 SRKW sightings in the Salish Sea. Sightings were concentrated in a few key hot spots, with an overall pattern of consistent presence in the Central Salish Sea during the summer months and a presence in Puget Sound proper during the fall and early winter months. A shift in SRKW presence in Puget Sound was documented in the late 1990s, possibly driven by increased foraging on fall chum salmon (Oncorhynchus keta) by 2 pods (‘K’ and ‘L’), and is consistent with the hypothesis that the movement patterns of these whales may be driven by prey availability. The Whale Museum’s dataset highlights the importance of long-term monitoring to document shifts that may take decades, and shows how opportunistic datasets can be valuable tools for illuminating spatial and temporal trends.

Citation

Larson, S., Olsen, J., & Osborne, R. (2018). Sightings of Southern Resident killer whales in the Salish Sea 1976-2014. Endangered Species Research. 14 pgs. 

Download the full article (Open Access)

About the Author: 
Jennifer K. Olson1, Jason Wood2, Richard W. Osborne3, Lance Barrett-Lennard4, Shawn Larson1: 1The Whale Museum, Friday Harbor, WA 98250, USA 2SMRU Consulting, Friday Harbor, WA 98250, USA 3University of Washington, Olympic Natural Resources Center, Forks, WA 98331, USA 4Coastal Ocean Research Institute, Ocean Wise, Vancouver, BC, V6B 3X8, Canada