Report Number: 12766
Reporting Year: 1995
Permit Number: CRLA1995AOLQ
Date Received: Jan 01, 1998
Principal Investigator:
Mark Buktenica,
National Park Service,
Crater Lake, Oregon
Additional investigator(s):
Dr Gary
Larson
Park-assigned Study Id. #
CRLA1995AOLQ
Permit Expiration Date:
Jan 01, 1998
Permit Start Date:
Jan 01, 1998
Study Starting Date:
Jan 01, 1995
Study Ending Date:
Jan 01, 1995
Study Status:
Completed
Activity Type:
Other
Subject/Discipline:
Fish / Ichthyology
Objectives:
Restore native bull trout to
historic numbers and distribution in Sun Creek, within the park, remove
non-native brook trout, and prevent re-invasion of non-native species in the
future.
Findings and Status:
A survey of fish populations and
stream habitat in Sun Creek during the summer of 1989 revealed a remnant
population (130 adult fish) of bull trout (Salvelinus confluentus) mixed with
introduced brook trout (S. fontinalis) in a 2 km section of stream.
Hybridization and competition with the brook trout threatened the bull trout
population with a high risk of extinction. A bull trout restoration plan was
drafted and peer reviewed in October, 1991. The goals of the plan were to
restore the remnant population of bull trout to historic numbers and
distribution in Sun Creek (within Crater Lake National Park), remove brook
trout, and prevent re-invasion of non-native fish. During the summer of 1992, a
restoration program was initiated. Brook trout were removed from Sun Creek with
electroshockers within and upstream of the bull trout section, and with a fish
toxin downstream of the bull trout section. Two log and rock fish immigration
barriers were constructed near the park boundary to prevent re-invasion of
non-native fish. Brook trout removal continues and a monitoring program is in
place to evaluate bull trout recovery.;The fourth field season of the bull trout
restoration project was completed in 1995. Our continued brook trout removal has
appeared to stop the decline of bull trout and temporarily stabilized bull trout
abundance. One hundred and eighteen bull trout were observed in 1995, 120 were
observed in 1994, 58 were observed in 1993, and 113 bull trout were observed in
1992. We hope to see an increase in bull trout abundance in 1997. Brook trout
removal efforts in the headwater section of Sun Creek have been completely
successful; no brook trout were observed during triple passelectrofishing above
the natural waterfall (fish migration barrier) in 1995. One brook trout was
found and removed above the falls in 1994, 22 were removed in 1993, and 234 were
removed in 1992. Within the bull trout section (upstream of the artificial
barriers and downstream of the natural waterfalls) 144 brook trout were removed
in 1995. Brook trout removal in the bull trout zone has reduced the brook trout
to bull trout ratio from approximately 3:1 in 1992, to 1:1 in 1995 prior to
annual brook trout removal.;Brook trout removal will continue and a monitoring
program is in place to evaluate bull trout and macroinvertebrate recovery.
For this study, were one or
more specimens collected and removed from the park but not destroyed during
analyses?
No
Funding provided this
reporting year by NPS:
55000
Funding provided this
reporting year by other sources:
5000
Full name of college or
university:
n/a
Annual funding provided by
NPS to university or college this reporting year: 0
