Fraser River sockeye salmon: data synthesis and cumulative impacts

Peterman: That was done and it does not explain the variation in the data as well as the aparameter. You can’t estimate simultaneously both the a and b parameters in a Kalmanfilter version of either the Ricker or Larkin models.Staley: Did you consider the shift in estimating recruitment for Fraser sockeye since the mid-1990s? Prior to that, apparently there was no en-route loss. Since then, recruitment isestimated as catch plus the Mission escapement estimate. How did you deal with that shift inaccounting for the trends?Peterman: It would only be relevant if en-route losses were occurring at a rate that wouldthrow the trend off.Marmorek: If they hadn’t added the en-route losses back into the estimates of recruitment,the trend would have been worse before the mid-1990s.Q/A: The first record of pre-spawning (en-route?) mortality was the 1992 return year.Marmorek: Did you see any pattern consistent with the Pacific Decadal Oscillation?Peterman: We did not look at that.Routledge: It seems the important conclusion was that the problem is in the ocean. I’m inclinedto agree but I’m not sure how strong the evidence is. Tahltan was only one stock, whichmakes me uneasy.Peterman: There were others that were not shown due to limited time.Routledge: That eases my concern.Peterman: There are not a lot of stocks that line up such that it allows you to do that analysis.Reynolds: Was Dorner’s work indicating more of a leaning towards freshwater?Dorner: There are also some patterns in freshwater, just from looking at it spatially, but I’mnot saying there is not also the large-scale ocean pattern. The freshwater pattern variesacross watersheds, in some cases covering stocks that don’t have the same oceanmigration routes.Peterman: These are not inconsistent messages. There are certain years where the interior BCand far northwest stocks are all red together (decreasing productivity) for a few years.They share the geographical area but we don’t have all the data. Brigitte Dorner also didstandard cluster analyses and you get different groupings of stocks, depending on whichclustering methods were used. Nothing produced a different picture than what you saw inthe animations.Cox: Harrison sockeye go out as fry. Do Pitt sockeye do the same?Johannes: They go out as smolts.Cox: Is there anything similar about their out-migration timing?Peterman: I unfortunately have no information on Pitt sockeye. There is some evidence forHarrison migration patterns, though. Beamish’s sampling studies found Harrisonjuveniles in northern Georgia Strait later in the season than other Fraser sockeye. Theyalso go to sea as fry rather than as smolts, and rear more in the Fraser River estuary32