[MARMAM] New Publication: Endangered predators and endangered prey: Seasonal diet of Southern Resident killer whales

Brad Hanson brad.hanson at noaa.gov
Fri Mar 5 16:56:54 PST 2021

Dear colleagues,

My co-authors and I are pleased to announce the publication of the 
following article:
Endangered predators and endangered prey: seasonal diet of Southern 
Resident killer whales.  Hanson, M.B., C.K. Emmons, M.J. Ford, M. 
Everett, K. Parsons, L.K. Park, J. Hempelmann, D.M. Van Doornik, G.S. 
Schorr, J.K.  Jacobsen, M.F. Sears, M.S. Sears, J.G. Sneva, R.W. Baird, 
L. Barre.  2021.   PLoS ONE 16(3): e0247031. 

Understanding diet is critical for conservation of endangered predators. 
Southern Resident killer whales (SRKW) (/Orcinus orca/) are an 
endangered population occurring primarily along the outer coast and 
inland waters of Washington and British Columbia. Insufficient prey has 
been identified as a factor limiting their recovery, so a clear 
understanding of their seasonal diet is a high conservation priority. 
Previous studies have shown that their summer diet in inland waters 
consists primarily of Chinook salmon (/Oncorhynchus tshawytscha/), 
despite that species’ rarity compared to some other salmonids. During 
other times of the year, when occurrence patterns include other portions 
of their range, their diet remains largely unknown. To address this data 
gap, we collected feces and prey remains from October to May 2004-2017 
in both the Salish Sea and outer coast waters. Using visual and genetic 
species identification for prey remains and genetic approaches for fecal 
samples, we characterized the diet of the SRKWs in fall, winter, and 
spring. Chinook salmon were identified as an important prey item 
year-round, averaging ~50% of their diet in the fall, increasing to 
70-80% in the mid-winter/early spring, and increasing to nearly 100% in 
the spring. Other salmon species and non-salmonid fishes, also made 
substantial dietary contributions. The relatively high species diversity 
in winter suggested a possible lack of Chinook salmon, probably due to 
seasonally lower densities, based on SRKW’s proclivity to selectively 
consume this species in other seasons. A wide diversity of Chinook 
salmon stocks were consumed, many of which are also at risk. Although 
outer coast Chinook samples included 14 stocks, four rivers systems 
accounted for over 90% of samples, predominantly the Columbia River. 
Increasing the abundance of Chinook salmon stocks that inhabit the 
whales’ winter range may be an effective conservation strategy for this 

The open-access article can be downloaded from

Any additional questions can be directed to me via email at 
brad.hanson at noaa.gov <mailto:brad.hanson at noaa.gov>

Brad Hanson

M. Bradley Hanson, Ph.D.
NOAA/NMFS/Northwest Fisheries Science Center
2725 Montlake Blvd. E
Seattle, WA 98112

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