Differential Estimates of Survival for PIT Tagged Fish Evidence and Causes

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Differential Estimates of Survival for PIT
Tagged Fish Evidence and Causes
Jason Vogel Nez Perce Tribe Department of
Fisheries Resources Management
LSRCP Annual Meeting March 4, 2008
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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?

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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

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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?

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Juvenile Passage Routes Through Hydrosystem
Percentages vary by species and hydro operations
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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

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Differences in Chinook SARs by Passage Route
Data from CSS 10-year Retrospective Report
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Bypassing Fish Equals Lower Adult Returns for
Spring/Summer Chinook
N405
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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 (RSWs, others)
• Risks/Costs
• PIT tagged fish treated differently
• Decreases adult returns

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Part II Effects of PIT Tags

• Current uses of PIT tags
• SAR calculations (LGRLGR, StreamStream)
• Adult run predictions
• In season adjustments of harvest and broodstock
  take and allocations
• Side by side comparisons of groups

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John Williams unpublished data
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John Williams unpublished data
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Snake River Chinook Salmon
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Snake River Chinook Salmon
Y 0.817 X - 0.0047 r2 0.941, P 0.006
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John Williams unpublished data
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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

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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)

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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

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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

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Acknowledgements

• John Williams NOAA
• Fish Passage Center - CSS
• Curt Knudsen Oncorh Consulting
• NPT Staff

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Questions?