Differential Estimates of “Survival” for PIT Tagged Fish – Evidence and Causes
Jason Vogel Nez Perce TribeDepartment of Fisheries Resources Management
LSRCP Annual Meeting March 4, 2008
Outline• Part I
– Ensure marking is necessary– Focus on PIT Tag marking– Filling critical research gaps– Benefits vs. risks
• Part II– Effects of actual PIT tag – What does PIT tag information give us?– Effects of actual PIT tag– Representative or not?
Nez Perce Tribe Department of Fisheries Resources Strategic Management Plan
Vision Manage aquatic resources to provide for healthy self-sustaining fish
populations of historically present species and for harvest opportunities
Guiding Principles Minimizing intrusive marking and handling of fish supports cultural
and spiritual beliefs, respect for the fish, and maximum survival
PIT Tag Marking is it Necessary?
• Baseline monitoring• Fill critical data gaps
– Information needed on groups of fish• Marking fish comes at a cost
– Initial and Delayed Mortality– Information gained needs to outweigh the cost of
decrease adult returns• How do we determine if marking is necessary
and at what level?– Science? – Policy?– Social and Cultural?
Bypassed = 3-10%
Undetected = 20 – 40 %
Transported = 55-75%
Juvenile Passage Routes Through Hydrosystem
Percentages vary by species and hydro operations
Choosing Where the Fish Go
• Bypassed = default action for PIT tags– Survival estimates of fish to and through the
hydrosystem
• Monitor Mode (mimic unmarked)– Representative SARs – Johnson Creek and Imnaha River for NPT
• Separation by Code– Comparative Survival Studies (CSS) = 70%
transported: 30% bypassed– Smolt to adult return rates of bypassed, transported,
and undetected juveniles
Differences in Chinook SARs by Passage Route
Data from CSS 10-year Retrospective Report
Rapid River SFSR/McCall Dworshak Imnaha Catherine Cr. Wild Chinook
Ave
rage
SA
Rs
LG
R t
o L
GR
0.000
0.005
0.010
0.015
0.020
0.025
SAR Transport SAR Bypasss
Rapid River SFSR/McCall Dworshak Imnaha Catherine Cr. Johnson Cr. Lostine R.
Sp
rin
g/S
um
mer
Ch
inoo
k A
du
lts
0
20
40
60
80
100
120
140
160
Annual Number of Adults NOT Returning
Bypassing Fish Equals Lower Adult Returns for Spring/Summer Chinook
N=405
Summary
• Benefits of PIT tagging fish– Comparison of groups/filling in critical gaps
• From release to facilities (treatment groups)
• Within the facilities treatment groups (barged, bypassed, others)
• Tests of hydro actions (RSW’s, others)
• Risks/Costs– PIT tagged fish treated differently– Decreases adult returns
Part II – Effects of PIT Tags
• Current uses of PIT tags
– SAR calculations (LGR:LGR, Stream:Stream)
– Adult run predictions
– In season adjustments of harvest and broodstock take and allocations
– Side by side comparisons of groups
1995 1996 1997 1998 1999 2000 2001 2002 20030
1
2
3
4PIT-taggedunmarked
Snake River wild Chinook salmon (LGR to LGR + catch)
Year of outmigration
Sm
olt-
to-a
dult
retu
rn -
% (
SA
R)
John Williams unpublished data
1994 1995 1996 1997 1998 1999 20000
1
2
3
4
5
PIT-tagged wildunmarked wild
PIT-tagged hatchery
Snake River steelhead
Year of outmigration
Sm
olt-
to-a
dult
retu
rn -
% (
SA
R)
John Williams unpublished data
NOAA
Non-PIT Tagged SAR at LGR
0.015 0.020 0.025 0.030 0.035
PIT
Tag
ged
SA
R a
t L
GR
0.005
0.010
0.015
0.020
0.025
99
00
01 02
98
Y = 0.710 * X - 0.0038r2 = 0.882, P = 0.018
Snake River Chinook Salmon
CSS
Non-PIT Tagged SAR at LGR
0.015 0.020 0.025 0.030 0.035
PIT
Tag
ged
SA
R a
t L
GR
0.005
0.010
0.015
0.020
0.025
99
00
01
02
98
Y = 0.817 * X - 0.0047r2 = 0.941, P = 0.006
Snake River Chinook Salmon
1995 1996 1997 1998 1999 2000 20010.0
0.5
1.0
1.5
2.0
Dworshak Hatchery Chinook salmon *
PIT
unmarked
Year of outmigration
Sm
olt-
to-a
dult
retu
rn -
% (
SA
R)
1995 1996 1997 1998 1999 2000 20010.0
0.5
1.0
1.5
2.0
Rapid River Hatchery Chinook salmon *
PITunmarked
Year of outmigration
Sm
olt-
to-a
dult
retu
rn -
% (
SA
R)
1995 1996 1997 1998 1999 2000 20010.0
0.5
1.0
1.5
2.0
McCall Hatchery Chinook salmon*
* Includes adjustment for harvest upstream of LGR
PITunmarked
Year of outmigration
Sm
olt-
to-a
dult
retu
rn -
% (
SA
R)
Hatchery to hatchery SARs - no adjustment for smolt survival toLGR or adult harvest downstream of LGR- Data after 2005 CSS report
John Williams unpublished data
What information do we have?• Lostine River (4 Broodyears)
– PIT tagged conventional underestimate SARs by 27%– PIT tagged captive brood underestimate SARs by 48%
• Captive Program (1994-2003)– Raise fish from parr to adult in captivity– Fish shedding PIT tags
• Catherine Creek 3.6% loss• Grande Ronde 2.3% loss• Lostine River 3.4% loss
• Johnson Creek (2 Broodyears)– Monitor mode PIT tagged fish underestimate SARs by
39%
What information do we have?
• Knudsen et al. (in review) 5 Broodyears– PIT tagged fish underestimate SARs by 25%. – Average of 18.4% fish lost their PIT tags. – After correcting for PIT tag loss, PIT tagged
fish had 10.3% lower SAR than untagged fish (Mortality)
Summary
• PIT tags are very useful for specific side by side experiments when absolute survival is not necessary
• PIT tagged fish do not represent an unbiased absolute measure of SARs
• Need to design specific experiments to look at mechanisms to test for differences– PIT tag loss/shed– Mortality caused by PIT tagging– Malfunction of PIT tag or inability to read
Conclusions
• Ensure the benefits outweigh costs when using PIT tags– In terms of decreased adult returns
• PIT tagged fish tend to underestimate SARs compared to untagged fish– Be very careful when utilizing PIT tags for absolute
measure of SARs for groups of fish• Current methods are conservative• Setting and modifying harvest seasons and broodstock
management
• Determine mechanisms for differences in PIT vs. unmarked fish
Acknowledgements
• John Williams – NOAA
• Fish Passage Center - CSS
• Curt Knudsen – Oncorh Consulting
• NPT Staff
Questions?
Top Related