We sampled and released
194 bull trout (Salvelinus confluentus) from the Tucannon
River in 2005. Passive Integrated Transponder (PIT) tags were inserted
in 105 of these individuals, and we detected existing PIT tags in
an additional 67 bull trout. Twenty-one of these fish were also surgically
implanted with radiotags, and we monitored their movements throughout
the year. Fourteen bull trout sampled at the Tucannon Hatchery weir
were not interrogated for PIT tags.
During 2005, we monitored
the movements and migration of eight bull trout that were tagged in
2004, and 21 bull trout that were tagged in 2005. The general movements
of these fish were typical of the movements we observed in this population
from radio-telemetry work in 2002-2004. Bull trout began their upstream
migration in late April through June, and continued on to the spawning
areas in the upper reaches of the Tucannon River and it’s tributaries
in July and August. The first post spawn outmigrant was sampled in
late September, and was followed by downstream movements typical of
post spawn activity throughout October. By late November and early
December, radio tagged bull trout were relatively stationary, and
were distributed from rm 36 at the Tucannon Hatchery downstream to
rm 1.8, near the confluence of the Tucannon and Snake Rivers.
Two bull trout outmigrated
into the reservoir influenced area of the lower Tucannon and Snake
rivers in January. One of these fish had been tagged during 2004,
and the other was tagged in the lower Tucannon River in January, 2005.
Both of these fish stayed in the reservoir influenced area until March,
when they began their return back to the Tucannon River. These two
fish are the first documented occurrences of bull trout from the Tucannon
River embarking on a seasonal migration to and from Lower Monumental
Pool. As in previous years, we did not collect data associated with
objectives 2, 3, or 4 of this study, because we were unable to monitor
migratory movement of radio-tagged bull trout into the vicinity of
the hydropower dams on the main stem Snake River.
