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Blitzen River Redband Trout
The Donner und Blitzen River in Malheur Lakes Basin
supports a unique, relatively abundant redband trout population where
both resident and migratory life histories are expressed. The
persistence of large migratory fish represents a life history that was
much more widespread among inland redband populations but is now
relatively rare because of anthropogenic alterations of flow regimes.
Historically, redband trout populations in the Malheur Lakes basin
connected through Malheur Lake. At the time, fish populations from
Silver Creek, the Silvies River, and the Donner und Blitzen River were
connected. Climate change, in addition to construction of irrigation
diversion dams, has reduced or eliminated connection between these
populations.
Since the early 20th
century, irrigation, habitat modifications, livestock grazing and the
introduction of non-native fish species have hindered connectivity and
decreased abundance on redband trout in the Blitzen River. As a result
the migratory life history is threatened by migration barriers, water
quality problems, and the presence of non-native species. The
lower Blitzen River has 8 irrigation dams and diversions and at the time
of construction most had little or no accommodation for fish passage.
Recent improvements to passage at irrigation diversion structures have
improved connectivity.
Preliminary examination show that individual dams were minimally
passable, but the collective impact of all dams on passage and migration
timing is still unknown.
In 2007 the Native Fish Investigations project, in conjunction with OSU
Department of Fisheries and Wildlife, conducted a radio telemetry study
to describe the movement patterns of adult redband trout in the Blitzen
River and evaluate the potential impact of human constructed barriers on
movement. The study examines physical impediments to migration, the
effects of altered stream temperature and flow, migrations distance and
timing, and location of spawning areas.
 Annual Reports and Publications:
Anderson, M. 2007. Migratory Life History of Redband Trout in the Donner und Blitzen River. Oregon Department of Fish and Wildlife Interim Report, Corvallis.
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