Differential Estimates of “Survival” for PIT Tagged Fish – Evidence and Causes Jason Vogel Nez Perce Tribe Department of Fisheries Resources Management.

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


Sm

olt-

to-a

dult

retu

rn -

% (

SA

R)


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


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


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


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


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?

Differential Estimates of “Survival” for PIT Tagged Fish – Evidence and Causes Jason Vogel Nez Perce Tribe Department of Fisheries Resources Management.

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