Kagley et a!.: Residency, partial migration, and late egress of Oncorhynchus tshawytscha and O, kisutch 
545 
marine period within protected waters of southeastern 
Alaska (Orsi and Jaenicke, 1996) and British Columbia 
(Healey and Groot, 1987). It has also been known for 
decades that some Chinook salmon, termed “residents,” 
are found throughout the year within Puget Sound, the 
Strait of Georgia, and associated inlets (Pressey 1 ; Haw 
et al. 2 ; Buckley, 1969). It has been unclear to what ex¬ 
tent these salmon move within the inland marine wa¬ 
ters, collectively known as the Salish Sea, and whether 
they leave for the coast at some point. Brannon and 
Setter (1989) inferred from coded wire tagging data 
that both maturing and immature Chinook salmon 
may make annual “loop” migrations from Puget Sound 
north into the Strait of Georgia in spring and sum¬ 
mer and then back south into Puget Sound. However, 
there is no direct evidence of individual fish making 
such migrations. 
Resident salmon seem to constitute a persistent and 
substantial fraction of the entire Puget Sound popula¬ 
tion of Chinook salmon. Analysis of coded-wire tag data 
indicated that an estimated 29% of hatchery Chinook 
salmon subyearlings and 45% of yearlings entering 
Puget Sound remained as residents (O’Neill and West, 
2009). Subsequent analyses based on similar data but 
reflecting a different analytical approach also revealed 
that many Puget Sound Chinook salmon adopt a resi¬ 
dent marine distribution pattern (Chamberlin et al., 
2011). This pattern occurs but is less common with 
coho salmon (O. kisutch ; Rohde et al., 2014). However, 
because coded wire tags document only the location 
where fish are captured, and not movement patterns, 
movements of individual fish cannot be determined 
with these tags. Research using hydroacoustic trans¬ 
mitters revealed differences between coho and Chinook 
salmon depth distributions and diel vertical migrations 
but did not provide information on movement through¬ 
out the basins in Puget Sound and the Salish Sea 
(Smith et al., 2015). Four Chinook salmon distribution 
patterns were observed in the Salish Sea (Arostegui et 
al., 2017), but information on resident Chinook salmon 
movements in the main basins of Puget Sound is still 
very limited. 
The Chinook salmon evolutionarily significant unit 
in Puget Sound is listed as threatened under the U.S. 
Endangered Species Act (Federal Register, 2005). A 
better understanding of the movements of these fish 
between Puget Sound and the coastal ocean, and 
within Puget Sound, will help to identify patterns in 
habitat use, to evaluate fishery management objec¬ 
tives across jurisdictional boundaries, and even help 
to determine pathways to contaminant exposure. Resi¬ 
dent Chinook salmon, for example, have higher accu¬ 
mulations of polychlorinated biphenyls (PCBs) than 
1 Pressey, R. T. 1953. The sport fishery for salmon on Puget 
Sound. Wash. Dep. Fish., Fish. Res. Pap. 1:33-48. 
2 Haw, F., H. O. Wendler, and G. Deschamps. 1967. Devel¬ 
opment of Washington State salmon sport fishery through 
1964. Wash. Dep. Fish., Res. Bull. 7, 192 p. [Available from 
website.] 
conspecifics that migrate to the coastal ocean (O’Neill 
and West, 2009). As a prey item these salmon contain 
high enough levels of persistent organic pollutants to 
have possible health effects on ESA-listed killer whales 
(Hickie et al., 2007; Cullon et al., 2009) and to require 
human health advisories (WDOH 3 ). 
In this study, individual Chinook salmon were im¬ 
planted with hydroacoustic tags at a time after the 
majority of salmon had typically left Puget Sound for 
ocean feeding grounds (Healey, 1991). The detections of 
these presumably resident Chinook salmon were used 
to determine: 1) whether these individuals remained 
within Puget Sound, and 2) whether origin (wild or 
hatchery), body size, or season of tagging influenced 
their tendency to remain in Puget Sound. For the fish 
that stayed as residents within Puget Sound, we also 
determined 3) whether resident salmon remained in 
the same region where they were tagged or moved 
throughout Puget Sound and parts of the Salish Sea, 
and 4) whether detections depended on the receiver lo¬ 
cation’s water depth and proximity to shore. 
Finally, we compared the location features of receiv¬ 
ers that recorded Chinook salmon with those features 
that were recorded with receivers that detected coho 
salmon collected and tagged at the same locations and 
times (Rohde et al., 2013). Coho and Chinook salmon 
in Puget Sound are ecologically similar and both ex¬ 
hibit partial migration (i.e., residency). The factors 
affecting residency, inferred from coded wire tagging 
data, were similar for the 2 species (Chamberlin et al., 
2011; Rohde et ah, 2014), and both species tended to 
be caught as residents in the natal basin where they 
entered Puget Sound. We therefore combined data from 
this study and that by Rohde et al. (2013) to compare 
directly the movement patterns of individual residents 
of these species in Puget Sound. 
Materials and methods 
Tagging 
On 9 dates in June (2006 and 2007), November (2006), 
and December (2006, 2007, and 2008), 87 Chinook 
salmon were caught with a commercial purse seine in 
central Puget Sound (tagging area, Fig. 1). On the ba¬ 
sis of the dates, locations, and sizes (range: 208-370 
mm in fork length) of these salmon, all were assumed 
to be residents at the time of capture. To determine 
residency we presumed that fish of this size would 
have entered salt water as smolts the previous spring 
or summer and were still in Puget Sound about a year 
later at a time when migratory individuals would be 
moving along the coast or in offshore waters of the 
North Pacific Ocean (Trudel et al., 2009). 
3 WDOH (Washington State Department of Health). 2006. 
Human health evaluation of contaminants in Puget Sound 
fish, 136 p. Div. Environ. Health, Wash. State Dep. Health, 
Olympia, WA. [Available from webiste.] 
