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. doi:10.1371/journal.pone.0247031
ABSTRACT
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 population.
The open-access article can be downloaded from
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247031
Any additional questions can be directed to me via email at brad.hanson@noaa.gov
Sincerely,
Brad Hanson
-- =========================================================== M. Bradley Hanson, Ph.D. NOAA/NMFS/Northwest Fisheries Science Center 2725 Montlake Blvd. E Seattle, WA 98112