97 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
established in 1881 -cf. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Insights, from genetic analyses, into stock-specific 
distribution of juvenile steelhead (Oncorhynchus 
my kiss) from the Columbia River during early 
marine migration 
Email address for contact author: don.vandoornik@noaa.gov 
Abstract —For anadromous Pacific 
salmon (Oncorhynchus sp.), ocean 
conditions during their initial entry 
into the marine environment can 
greatly affect their survival. Dif¬ 
ferent life history types or stocks 
may experience different conditions 
during their marine entry because 
routes of early marine migration 
can differ among types or stocks. 
Steelhead (O. mykiss) from the Co¬ 
lumbia River are believed to migrate 
offshore quickly once they enter the 
ocean, but little is known about 
whether life history or stock-specific 
differences in early marine migra¬ 
tion exist. We assembled a baseline 
of steelhead genetic data that al¬ 
lowed us to estimate the genetic 
stock of origin for juvenile steelhead 
that had been caught off the coasts 
of Washington and Oregon in May, 
shortly after their out-migration 
from freshwater. We found differ¬ 
ences in the average locations of 
the various genetic stock groups of 
the Columbia River, dissimilarities 
that were most likely due to differ¬ 
ences in the timing of the marine 
entry of juveniles. We also observed 
considerable variation among years 
in the average location where we 
caught steelhead and in the number 
of steelhead caught, results indicat¬ 
ing that freshwater or marine condi¬ 
tions can influence the behavior or 
survival of steelhead. 
Manuscript submitted 25 July 2018. 
Manuscript accepted 11 April 2019. 
Fish. Bull. 117:97-106 (2019). 
Online publication date: 26 April 2019. 
doi: 10.7755/FB. 117.1-2.11 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Donald M. Van Doornik (contact author) 1 
David R. Kuligowski 1 
Cheryl A. Morgan 2 
Brian J. Burke 3 
Todd R. Seamons 4 
1 Conservation Biology Division 
Northwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7305 Beach Drive East 
Port Orchard, Washington 98366 
2 Cooperative Institute for Marine Resources 
Studies 
Hatfield Marine Science Center 
Oregon State University 
2030 South Marine Science Drive 
Newport, Oregon 97365 
Anadromous Pacific salmon (On- 
corhynchus sp.) utilize the marine 
environment for rapid growth to ma¬ 
turity. Results of studies have indi¬ 
cated that the initial months after 
entry into saltwater are important 
to the survival of steelhead and that 
this time period affects year-class 
strength (Pearcy, 1992; Hare and 
Francis, 1995). Therefore, under¬ 
standing their marine distribution 
and migration, and how they respond 
to different marine conditions dur¬ 
ing those initial months, can provide 
knowledge of the variables that con¬ 
tribute to strong year classes. 
The Columbia River is home to 
several species of salmonids, many 
of which have been listed as threat¬ 
ened or endangered under the U.S. 
Endangered Species Act, including 
steelhead (Oncorhynchus mykiss ). 
Steelhead are the life history vari¬ 
ant of O. fnykiss that migrate from 
3 Fish Ecology Division 
Northwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2725 Montlake Boulevard East 
Seattle, Washington 98112 
4 Washington Department of Fish and Wildlife 
1111 Washington Street Southeast 
Olympia, Washington 98501 
their place of birth in freshwater to 
the ocean, where they remain for 
several years before returning to 
their river of origin to spawn. For 
steelhead from the Columbia River 
Basin, populations in the Lower, 
Middle, and Upper Columbia, Upper 
Willamette, and Snake Rivers are 
listed as threatened (NWFSC, 2015). 
Despite the imperiled status of these 
populations, the greatest number of 
steelhead in the Pacific Northwest 
are produced in the Columbia River 
(Busby et al., 1996), contributing 
significantly to highly valued recre¬ 
ational and tribal fisheries through¬ 
out the region. 
The Columbia River contains 2 
phylogenetic groups (subspecies) of 
steelhead that are separated by the 
Cascade Mountain Range: coastal 
steelhead ( O. mykiss irideus) and 
Columbia River redband steelhead 
( O. mykiss gairdnerii), the latter 
