D'Alessandro and Duffield: Salmonid tags found in a Phocoena phocoena in southwestern Washington 
307 
migrate in huge schools in the tributaries (Kern 4 ), it is 
possible that the juvenile Chinook salmon tagged with the 
tags found in the harbor porpoise had gathered in large 
densities at the mouth of the Columbia River before head¬ 
ing into the Pacific Ocean. This gathering would have made 
them more vulnerable to one or more foraging events by 
the harbor porpoise. These foraging events were likely 
opportunistic because literature review does not support 
the notion that salmonids are regular prey in the diet of 
harbor porpoises along the west coast of North America 
(Scheffer and Slipp, 1948; Wilke and Kenyon, 1952; Schef¬ 
fer, 1953; Jones, 1981; Treacy 5 ; Gearin et al., 1994; Walker 
et al. 6 ). However, Treacy 5 identified salmonid remains in 1 
harbor porpoise recovered from the Columbia River area, 
and Gearin et al. (1994) identified remains of coho salmon 
(O. kisutch ) in 1 harbor porpoise that was taken in a Chi¬ 
nook salmon set net in Washington. 
Other than the PIT tags and CWTs in the harbor por¬ 
poise stranded in August 2012 and the PIT tags found in 
2 other harbor porpoises, we have not found any salmonid 
CWTs or PIT tags in the more than 150 stomachs that 
we have examined since 2007 from dead harbor porpoises 
stranded within our area from northern Oregon to south¬ 
ern Washington. One PIT tag that had been inserted into 
a juvenile winter-run steelhead from a hatchery in the 
Columbia River Basin was recovered from the forestom¬ 
ach of an adult male harbor porpoise that was stranded on 
8 June 2012 in Arch Cape, 30 miles south of the Columbia 
River plume. This steelhead came from the Oak Springs 
Hatchery in Maupin, Oregon, and was released in an 
acclimation pond of the sand trap in the East Fork Hood 
River in Oregon on 9 May 2012. This fish was not detected 
elsewhere downstream of its release site. The other PIT 
tag was recovered from the stomach of an adult male har¬ 
bor porpoise that was stranded on 19 May 2014 on the 
Long Beach Peninsula, just north of the Columbia River 
plume. This PIT tag came from a wild summer-run steel¬ 
head that was tagged and released in Idaho on 7 Septem¬ 
ber 2013. This wild steelhead was detected on 6 May 2014 
4 Kern, C. 2012. Personal commun. Fish Div., Oregon Dep. Fish 
Wildl., 4034 Fairview Ind. Dr. SE, Salem, OR 97302. 
5 Treacy, S. D. 1985. Feeding habits of marine mammals from 
Grays Harbor, Washington to Netarts Bay, Oregon. In Marine 
mammals and their interactions with fisheries of the Columbia 
River and adjacent waters, 1980-1982, p. 149-198. NOAA, Natl. 
Mar. Fish. Serv., Northwest Alaska Fish. Sci. Cent. NWAFC Pro¬ 
cessed Rep. 85-04. [Available from website.] 
6 Walker, W.A., M. B. Hanson, R. W. Baird, and T. J. Guenther. 
1998. Food habits of the harbor porpoise, Phocoena phocoena, 
and Dali’s porpoise, Phocoenoides dalli, in the inland waters of 
British Columbia and Washington. In Marine Mammal Protec¬ 
tion Act and Endangered Species Act implementation program 
1997 (P. S. Hill, B. Jones, and D. P. DeMaster, eds.), p. 63-75. 
NOAA, Natl. Mar. Fish. Serv., Alaska Fish. Sci. Cent. AFSC Pro¬ 
cessed Rep. 98-10. [Available from website.] 
at the juvenile bypass facility of the Lower Granite Dam 
in southeastern Washington and on 10 May 2014 near 
Wauna, Oregon. 
Although Chinook salmon have been identified as prey 
for other marine mammals, such as the California sea lion 
(.Zalophus californianus), Steller sea lion ( Eumetopias 
jubatus ), harbor seal (Phoca vitulina), and killer whale 
(Orcinus orca ), in the Puget Sound region of Washing¬ 
ton (see Chasco et al., 2017), this report is the first one of 
known predation of juvenile Chinook salmon by a harbor 
porpoise in the Pacific Northwest, adding to the knowl¬ 
edge of feeding habits of harbor porpoises. 
Acknowledgments 
We would especially like to thank C. Kern of the ODFW for 
providing information regarding the PIT tags and CWTs, 
assisting us with interpretation of tag data, and address¬ 
ing other general hatchery-related questions. We are also 
grateful for the tag coordinators who provided data related 
to PIT tags. Lastly, a huge thank you to M. Hughes from 
the Biology Department at Portland State University for 
her efforts in generating the map. 
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S. Pearson, et al. 
2017. Estimates of Chinook salmon consumption in Wash¬ 
ington State inland waters by four marine mammal 
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Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. 
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1994. Harbor porpoise interactions with a Chinook salmon 
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