Fraser River sockeye salmon: data synthesis and cumulative impacts

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Information gaps: The most important unknown is ecosystem monitoring for key predators.Information is poor for the open ocean and in freshwater. DFO’s attempts to implementintegrated management have been very limited and the recent ecosystem initiative was so poorlyfunded as to be meaningless. Key research needs include learning more about the abundance ofnon-commercial species and what’s happening in the open ocean.DiscussionPeterman: You have made an important point that sockeye could represent only 0.1% of the dietof dogfish and still suffer significant impact, given the abundance of the latter. We need to dothe rest of these calculations. We haven’t got the total salmon biomass that could be eaten bymarine mammals.Christensen: We can say let’s have an experimental fishery. Stomach samples reveal the averagediet. With DNA, you can identify prey that comprises only a very small proportion of thediet.Trites: It’s very simple to do the next step of putting a number on it. We need to do it for the fishas well because the fish eat far more. A big part of the diet of harbour seals was hake. Whatare those hake eating? So the seals could also be controlling other salmon predators, thushaving a positive as well as a negative impact. You can’t just put one number out withoutcontext – ecosystem models are important.Christensen: It’s very clear from this that we can’t point to one single species so we are probablylooking at cumulative effects.McKinnell: We also have to consider the behaviour of these species. Which predators have abehaviour that could put them in contact with high densities of outgoing sockeye smolts (e.g.which ones operate in the top 10 metres of water)?Christensen: This highlights the point in the quote about the salmon ocean refuge being 10miles offshore. About 15% of recent sockeye samples had daggertooth wounds.McKinnell: Regarding the diet of salmon sharks, it’s important to ensure that the target speciesfor the fishery where they are caught for stomach analysis was for salmon sharks. They willeat whatever else is in the net, so if they are caught in a salmon fishery, that will create bias.Routledge: Do Pacific mackerel only come north when the ocean is warmer?Christensen: That was not a major part of the argument. What is important is the big changeshappening in the Gulf of Alaska.Routledge: It has been hypothesized that mackerel are a major predator during El Nino events.Christensen: I don’t know.Martin: There has been a large change in the biomass of pilchards and mackerel over time.Christensen: There are now studies showing how much individual salmon sharks move aroundbut little is known about overall populations.Trites: Stellar sea lions are probably the ones that have been best studied, and pilchards show upin their diets when there are big changes.Dorner: The likely suspects are in the Gulf of Alaska, but Alaska stocks have not been affected.57
Christensen: Bristol Bay stocks are distributed further to the west. These changes are more in theGulf of Alaska.McKinnell: Those predators live largely on the ocean shelf and sockeye are mostly distributedoff the shelf.Christensen: That is true after they leave the coast but smolts have to pass through the shelf aswell.McKinnell: So do the Bristol Bay fish.Peterman: This provides a good summary of a lot of things that were not in the PSC report.Important issues include alternate prey and what is happening with other salmon species (e.g.very high Fraser pink abundance) and the study that showed total salmon abundance in theNorth Pacific is at an all-time high.Christensen: Plus the issue of very high pink and chum hatchery releases.Peterman: Sometimes diet indicates different distribution. Conversely finding few sockeye in thediet can reflect low sockeye abundance.Trites: But there was evidence with the killer whale study where the sockeye were there and theywere not selecting them.English: Re Beamish’s juvenile salmon abundance surveys in Georgia Strait, was informationrequested on the other species caught?Christensen: We requested but did not receive information from DFO. There are indications thatthey caught quite a few potential predators in those surveys.English: Especially important is evidence of trends in abundance for alternate prey. Sandlance,anchovies, etc are said to be down but that should show up in Beamish’s surveys.Christensen: Hake is another interesting one but information on hake in Georgia Strait is verypoor.English: There were studies on early marine survival in the 1980s. Much of the focus was oninteractions with Chinook but there were also data on Barkley Sound sockeye. Is there anyinformation on increasing humpback whale populations in the Gulf of Alaska and anypotential for a shift to preying on salmon smolts?Trites: There are observations around Langara but we don’t see the same bubblehead feedingbehaviour. That’s the group most likely to be getting smolts and we need to do more workbut we don’t see the same feeding behaviour. We do know that they are taking a lot ofpilchards off Vancouver Island.Hinch: We shouldn’t lose sight of what happens in freshwater. There was a tagging study of 200smolts last year and half had disappeared by the mouth of the Fraser. We saw predation occurearly in the migration.Christensen: Agreed. I’m surprised that isn’t known.Trites: I’m looking for feedback or insights as to possible reasons or behaviour that mightexplain why we are not finding sockeye taken by killer whales.58
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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
Page 295 and 296: and scope for improvement, particul
Page 297 and 298: Workshop participants pointed out t
Page 299 and 300: o Can you find the same shared tren
Page 301 and 302: generally better for Alaska sockeye
Page 303 and 304: Relative Likelihood of Alternative
Page 305: There was widespread agreement with
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 348 and 349: Fraser sockeye salmon habitat analy
Page 350 and 351: survey data, but they were looking
Page 352 and 353: was also shown that tagged fish ret
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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Fraser River sockeye salmon: data synthesis and cumulative impacts

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