Hooking mortality & behavior of a Puget Sound population
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Transcript of Hooking mortality & behavior of a Puget Sound population
Hooking mortality & behavior of a Puget Sound population Charmane Ashbrook, Michael Mizell, & Ken Warheit
Tomelleri
ESA listingSport selective fishery impacts?
More reasonsVariable survival estimatesUse a control to extricate effects of
handling and tagging
PlanPart A, estimate survivalPart B, estimate encounter rate
Together, these estimates enable us to estimate the impact of sport selective fisheries on wild steelhead.
Example:Yearly escapement --1000 wild fish return
50% encounter rate --500 captured with sport gear
95 % survival rate -- 475 lived following release from sport gear
5% mortality rate --25 killed by sport gear
PlanPart A, estimate immediate and post-release survivalPart B, estimate encounter rate
Together, these estimates enable us to estimate the impact of sport selective fisheries on wild steelhead.
Example:Yearly escapement --1000 wild fish return
50% encounter rate --500 captured with sport gear
95 % survival rate -- 475 lived following release from sport gear
5% mortality rate --25 killed by sport gear
PlanPart A, estimate immediate and post-release survivalPart B, estimate encounter rate
Together, these estimates enable us to estimate the impact of sport selective fisheries on wild steelhead.
Example:Yearly escapement --1000 wild fish return
50% encounter rate --500 captured with sport gear
95 % survival rate -- 475 lived following release from sport gear
5% mortality rate --25 killed by sport gear
MethodsCapture 30 wild winter steelhead on hook and lineCapture 30 control fish Radio tag –small population, follow movementInsert tags surgically, potential iteroparityTrack fish using fixed and mobile (vehicle) receiversTwo year studyTag fish regardless of wounds, bleedingCollect photo, length, scale, DNA, and weight dataUse GIS to track fish
Methods II Three parts to survival
1. Immediate : from capture until release
2. Post-release: from release until presumed spawning
3. Out-migration: from presumed spawning until out-migrate from river (kelt)
Pre-season 2009: Little water problem
Results IControl fish (trap)2008: 122009: 7
Control X fish (previously hooked)2008: 7 2009: 1
Treatment fish (sport)2008: 27 2009: 27
Estimating survival
Conceptual example :
Immediate + post-release = total survival
by Keeley, E.R.
Results II --survivalGroup Immediate
survivalPost-release to
presumed spawning Survival
Control 100% 100%
Control X 100% 100%
Treatment 100% 100%
Estimating survival--take two
Conceptual example using out-migration as proxy for spawning:
Immediate + post-release + out-migration = total survival
Results III --survivalGroup Kelted
after spawning
Sample size
Survival relative to control %
90% confidence
intervals
2008 Treatment 17 27 75.56 51.2-99.9
2009 Treatment 22 27 95.06 67.0-100.0
Average Treatment
---------- ---------- 85.31 -------------
2008 Control X 5 7 85.71 47.4-100.0
2009 Control X 1 0 0.00 ------
2008 Control 10 12 ----- ---------
2009 Control 6 7 ----- ---------
There is a cost to being captured with sport gear.
Results IV--age structureAge Number
for 2008
Number for 2009
Notes
2.1+ 15 21 One fish had one spawning check (2009)
2.2+ 7 4
3.1+ 4 0 One fish had one spawning check (2008)
3.2+ 4 0
R.1+
10 5
R.2+
6 0 One fish had 2 spawning checks (2008)Samish steelhead can spawn multiple times but most
spawn only once and after 1 year in saltwater.
Results V --Gender Year Group Live
dDied Total
2008 Female
22 5 27
2008 Male 11 8 19
2008 Both 33 13 46
2009 Female
13 2 15
2009 Male 15 4 19
2009 Both 28 6 34
2008 more females out-migrated (kelted) than males. Consistent with other studies and evolutionary theory.
2008 Chi square test p=0.082009 Chi square test p=0.56
Results VI--DNA analysis 2009 group had 5 fish with hatchery parentage
3 controls and 2 treatment3 kelted2 with 2.1+ age structure; 2 spawn checkFeb 23rd to Mar 28th
2008 group had 8 fish with hatchery parentage7 controls and 1 treatment7 kelted3 with 3+ age structure; 1 spawn checkFeb 7th to Mar 6th
Comparison with other researchEvolution of hooking mortality studies, technology
& statistical improvementsRecent studies
California, summers, n=126 hook location & temperature >21C. 1995 & 1996. Fish observed for 36 hours.
British Columbia, winters, n=226 radio tag. Tag regurgitation, no control, bleeding fish not included?
Conclusions
There is a biological cost to sport fishing, 15%
Relatively high kelting rate may be typical for this kind of stream, low gradient and near saltwater
Fair % of “wild” fish had hatchery influence
Despite high kelting rate, relatively few fish were > first time spawners based on scale analysis
Further explorationsEvaluate in higher gradient, further in-river system;
fish that must travel further may have a lower survival In estuary environment survival will likely be lowerEstimate recapture survival Kelt migration and movement patterns in saltwaterConsider if management objective to separate
hatchery and wild fish based on return timing is successful
Summer steelhead survival may be lower because of warmer water and longer time in freshwater
Estimate encounter rate to estimate impact to population
Acknowledgements
Samish Hatchery CrewBob Leland & Steve Schroder Equipment: USGS, University of Idaho, &
Pete HahnTechnicians: Jen Mertes, Ryan Regner, Jim
Crook, Faith Sandretzky, and Kyle Gulbranson
Earl Steele and his fisheries class at Bellingham Technical College; Jim Naranovich
Fishermen: Brett Barkdull, Curt Kraemer, and local volunteers
Hook location
Treatment (sport caught)34 maxillary1 behind eye3 snout1 top of head1 no data
Control X (hatchery weir, previously hooked)6 maxillary1 no data
Artificial baitCorkyEggsFloatSand shrimpYarn
Fishing gear
Gender
2009Group Control Treatmen
tHooked Control
Female 4 13 0Male 3 13 1Unknown
0 1 0
Both 7 27 1
2008Group Control Treatmen
tHooked Control
Female 8 15 4Male 4 12 3Unknown
0 0 0
Both 12 27 7