Fraser River sockeye salmon: data synthesis and cumulative impacts

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was also shown that tagged fish returned to the river suffered much higher mortality if they hadbeen kept in warmer water. It’s still not understood why the fish are migrating earlier but theyare returning in poor physiological condition and then they encounter much higher rivertemperatures.Pre-spawn mortality: There is a long history of information showing that this affects all stocks,with mortality of up to 90%. Occurrences are variable and episodic among years and may behigher and more variable in recent years. There does not appear to be an overall trend for Frasersockeye but it does appear to be higher and more variable in Late-run stocks.There are many causes of PSM, including disease, stress and time spent on spawning grounds.There is evidence that it is simply a continuation of the processes that are killing fish during theirreturn migration.Conclusions: Migration mortality is substantial in many stocks across all run-timing groups inrecent years, particularly when river migration temperatures exceed 18 degrees C. Lab and fieldstudies show there are stock-specific differences in how fish deal with acute and chronic hightemperatures. Migration mortality is likely a contributing factor in declining trends in spawningabundance for stocks that don’t cope well with high temperatures (early and late runs). Prespawnmortality reduces the number of effective female spawners and could be a factor indeclining productivity for some late-run stocks.DFO and others are starting to do studies on possible inter-generational effects, but results todate are limited and equivocal.This study agrees with the three conclusions from the PSC report regarding en-route mortality,pre-spawn mortality and intergenerational effects.Information gaps: These include intergenerational effects, direct measures of migrationsurvival, and effects of bycatch/discard releases on survival. All three of these information needsare knowable.Climate & climate change effects on Fraser sockeye: literature reviewEduardo MartinsThe study objectives were to review the literature on documented effects of climate on sockeyeand to make a qualitative assessment of the role of recent climate change on the decline in Frasersockeye productivity.The presentation discusses how the literature was compiled, climate change and its effects onFraser sockeye habitats, the likelihood of climate change effects on survival, survival by lifestageand the likelihood of changes.A search was undertaken of primary and grey literature specific to sockeye. Most of the papersfocused on freshwater, though there have been more papers on the marine in the past 2 - 3 years.Climate change and Fraser sockeye habitats: Summer temperatures in the Fraser River havewarmed by 2 degrees C since the 1950s, and 13 of the last 20 summers have been the warmest onrecord. There have also been substantial changes in precipitation (an average increase of 22% percentury but highly variable across BC). Fraser River flows show no trend, though the freshet isslightly earlier. For Georgia Strait and the Gulf of Alaska, temperatures have warmed by 0.2563
degrees C per decade, but that trend is confounded by large trends like the ENSO and PDO, witha warming trend attributed to the 1977-97 PDO.Likelihood of climate change effects: Climate changes could affect phenology, growth andsurvival, thought this study only examined direct (observations and tagging) and indirect(productivity) evidence of changes in survival. Criteria were defined for ratings of Unlikely,Possible, Likely and Very likely.Egg and alevin survival: One study showed survival decreased when there were increasedflows during incubation. Another showed productivity increased in years with more rainfall,which may mean more spawning area. So the two factors may offset each other. The rating wastherefore that survival possibly decreased. Additional comments are that there may be inter-stockvariability, with coastal (Weaver) doing better than interior (Adams) stocks.Fry survival: Evidence from lab and field studies suggests that higher temperature possiblydecreased fry survival. Temperature may not affect fry survival directly but it may lead toincreased predation rates on fry (one study suggested that coho predation on sockeye increasedwith temperature). A study in the Columbia showed small-mouth bass and walleye increasedpredation on sockeye fry by 25% to 35%.Smolt and post-smolt survival: There is no lab but much field data indicating that temperaturesin the ocean and estuary area decreased survival, so this was rated as likely decreased. Additionalcomments are that opposite effects were seen in Alaska stocks. Temperature might be a proxy forchanges in food abundance, quality and/or increased predation, but we don’t know.Immature sockeye survival: There are no lab and just one field study suggesting thattemperature decreased survival. This was rated as possibly decreased, but there is very little dataAdult survival: There is much lab and field work showing that temperature reduces survival,and some field study showing that high flow decreases survival, so this was rated as very likelydecreased. Studies show low survival across many sockeye stocks at 18 – 20 degrees C, withinter-stock variability. Mechanisms for this are relatively well known and there is recentevidence that female survival and spawning success is exacerbated by warmer temperatures.Possible intergenerational effects need to be considered.Concluding remarks: More data is needed: different stocks have different life histories so theyexperience effects differently and this could provide valuable clues. More studies of mechanismsare also needed.Cumulative effects: Climate itself could be a significant factor generating a number ofcumulative effects. If sockeye adults return smaller and with less energy, they will be moresusceptible to stressors during the return migration. Impacts may also be nested: there may beeffects across all life stages and there may also be intergenerational effects with climate playinga role.Conclusion: Climate change is a possible contributor to recent declines in Fraser sockeyeproductivity on average, with inter-annual and inter-stock variability.DiscussionWoodruff: Is there any information for 2010 on holding patterns for Late-run sockeye in GeorgiaStrait?64
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April 2011technical report 6Fraser
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Stage 2: Smolt OutmigrationWe analy
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of multiple stressors and factors,
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4.3.5 Other evidence ..............
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List of TablesTable 4.2-1. Evaluati
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List of FiguresFigure 2.3-1. Cumula
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these integrative frameworks, conve
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2.0 Cumulative Impacts or Effects2.
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assumed that there is no potential
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classes of stressors. However, if s
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affected by many stressors over its
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examples illustrate this problem --
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possibly even negligible component
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Figure 3.3-1. The conceptual model
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3.3.3 Life history perspective/appr
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additional analyses to gain further
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Figure 3.3-3. Flow diagram used to
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This project is unusual in its scop
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4.0 Results, Synthesis and Discussi
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Peterman and Dorner (2011) have thr
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Figure 4.1-3. Estimates of long ter
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Figure 4.1-5. A) Total run size of
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Figure 4.1-6. Aggregate returns to
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o were generally worse during the l
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Freshwater predators on juvenile so
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copper, iron, mercury and silver).
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Several analyses by MacDonald et al
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abundances (Sproat, Klukshu, Chilka
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feel reasonably confident in this c
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Nelitz et al. (2011; Table 18) foun
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in the Lower Fraser than other Fras
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stressors. Thus our conclusions hav
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There are many marine predators tha
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assumption that exposure occurs whe
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observations that are then averaged
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Johannes et al. (2011) demonstrate
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“likely” contributor to the ove
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Table 4.4-2. Model specifications f
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Region Variable M1 M2 M3 M4 M5 M6 M
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3. survival rates within key portio
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2011). The thermal limit hypothesis
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Historically, the majority of retur
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salinity. There is much evidence th
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declines (discussed in section 4.2
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There is indisputable evidence of t
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Figure 4.6-2. Number of years that
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correlation was statistically signi
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4.6.7 Key things we need to know be
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al (2010). The combined effect of a
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more likely to suffer en-route and
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Table 4.7-2. Variables included in
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However, an important limitation is
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Alternative PreyVariablesModelsM1 M
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will likely have a high correlation
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5.0 Conclusion5.1 Important Contrib
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Stage 5: Migration back to SpawnWhi
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More specifically, the extended res
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The twelve highest priority recomme
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Life stagefor FraserRiversockeyesal
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6.0 ReferencesAinsworth, L.M., Rout
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Johannes, M.R.S., R. Hoogendoorn, R
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Schaller et al. 2007. Comparative S
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utilized to clarify the full range
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Appendix 2. Reviewer Evaluations an
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the conclusions of the Expert Panel
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Response: Figure numbers have been
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Response: This section has been com
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ased on time or other stocks) to
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them in terms of how changes in spa
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efer to some variable being include
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... (Table xx)". Structures of thes
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Report Title: Fraser River sockeye
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show stronger correlations. Hence,
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Fraser and non-Fraser sockeye popul
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a single database for other researc
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Response: We have removed the itali
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evidence unique to each life stage.
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Report Title: Data Synthesis and Cu
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Response: We have further emphasize
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5. I would also encourage the autho
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events occur, it should be possible
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I don’t have anything to add beyo
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constitutes an exposure to human ac
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3.3.1 has been revised to say “As
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most likely contributors to the rec
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A3.2.1 Integrative quantitative met
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Table A3.3-1. A summary of data set
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ProjectNumber Project Name Variable
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ProjectNumber Project Name Variable
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A3.4 Data PreparationContractor dat
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Table A3.4-2. An example entry in t
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Table A3.4-5. Brood year adjustment
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Table A3.4-7. Example output from t
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Table A3.4-9. The table of contents
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ProjectNumberProject Variable Subse
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The objective of our approach is to
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investigated ecosystems” (Burkhar
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Figure A3.5-1. Flow diagram used to
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multiple stresses simultaneously. T
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Change point analysis of productivi
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Figure A3.5-1. This is an example o
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ecruits for this analysis as we wan
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exclude covariates with limited yea
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Figure A3.5-3. Average chlorophyll
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Status only data setsIn many cases
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The A-series of model sets based on
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with this report given the vast sco
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Table A3.5-5. Example of the model
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categories of stressors. We cannot
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o In some cases it may be the timin
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Appendix 4. Quantitative ResultsA4.
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alance” over time and so this it
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Figure A4.2-3. Stock composition fo
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Figure A4.2-5. Stock composition fo
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A4.3 Multiple Regression ResultsA4.
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Life stage Stressor category Variab
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The results show strong support for
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ModelSet_A4c_VarName M1 M2 M3 M4 M5
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Table A4.3-7. Estimates for all fix
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A4.3.3Analyses by stressor category
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Table A4.3-10. Estimates for all fi
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Model: B4bBrood years: 1969-2001We
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A4.3.4Analysis by regionModel: C4a1
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suggest any underlying mechanism, b
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Model: C1a1996-2004For 1996-2004, i
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Table A4.3-23. SoG C1a candidate mo
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Appendix 5. Data Template User Guid
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Metric Connected to Biologically-su
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Initial Conceptual Model (Worksheet
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Commentsopen again. It is acceptabl
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Appendix 6. Workshop Report 1 (Nov.
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Table of ContentsTable of Contents
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PresentationsProductivity Dynamics
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and scope for improvement, particul
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Workshop participants pointed out t
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o Can you find the same shared tren
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Page 303 and 304: Relative Likelihood of Alternative
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Page 308 and 309: Appendix A: List of Projects and In
Page 310 and 311: Peer Reviewers: Provide constructiv
Page 312 and 313: MacDonald Environmental Sciences Lt
Page 314 and 315: Appendix C: Workshop MinutesContent
Page 316 and 317: Levy urged researchers to bear in m
Page 318 and 319: within-population, within-brood-yea
Page 320 and 321: To address potential skepticism ove
Page 322 and 323: instead of migrating directly out i
Page 324 and 325: considered a good surrogate of temp
Page 326 and 327: Bristol Bay review: There are subst
Page 328 and 329: Method: The approach included formu
Page 330 and 331: Staley: Our project needs to compar
Page 332 and 333: Levy: It will go ahead in January.
Page 334 and 335: preliminary assessment of potential
Page 336 and 337: MacDonald: We’re waiting for all
Page 338 and 339: including Shuswap and North Thompso
Page 340 and 341: and biological variables. The combi
Page 342 and 343: temperatures. Notably, it doesn’t
Page 344 and 345: Seasonal population distribution pa
Page 346 and 347: Information gaps: The most importan
Page 348 and 349: Fraser sockeye salmon habitat analy
Page 350 and 351: survey data, but they were looking
Page 354 and 355: English: There was extensive holdin
Page 356 and 357: periods showed that 4 to 6 stocks (
Page 358 and 359: Q/A: Researchers should also feel f
Page 360 and 361: Peterman: We’re lacking the big p
Page 362 and 363: Appendix D: Table of likelihood/ hy
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