Fraser River sockeye salmon: data synthesis and cumulative impacts

Challenges and OpportunitiesDave Marmorek, ESSAIt’s useful to think of all the science contractors as one science panel probing the evidence. Thiswork seeks to build on the most recent PSC report, regarding the evidence for and againstdifferent factors. Contractors should build on that report, but not be constrained by it. If those ofyou who attended the PSC workshop reached different conclusions (say you found betterindicators), provide evidence for changing your conclusions. Understand the pattern and thenseek the causes. Look at patterns over space and time and between stocks to say which suspectsor combination of suspects are most likely.The cumulative effects project, which will be discussed further on Day 2, is looking at therelative importance of different factors and which are most relevant, and also at combined effectsor causal mechanisms that may be inter-related (e.g. various impacts stemming from climatechange).If the workshop produces a long list of priorities, that is not useful. Think about what decisionsare affected by the information (e.g. If I knew X what would I do differently) and whether thereis a role for real management experiments and if so on what scale.There are different forms of indirect evidence that we can think about. Even if there is imperfectevidence, can we still see contrast across different stocks or across time or space?Research program presentationsProductivity dynamics of sockeye salmon: patterns that need to beexplainedRandall Peterman & Brigitte DornerThis presentation covered data and methods, spatial and temporal patterns in productivity forFraser and non-Fraser sockeye stocks, stocks with similar patterns, and conclusions and anemergent hypothesis.Background: The disastrous 2009 Fraser sockeye return (1.5 million adults, the lowest since1947) was just the latest in a decades-long decline in abundance and productivity (returningadults per spawner) for Fraser sockeye. The Fraser saw peak runs of up to 40 million sockeyeevery fourth year until the 1913 Hells Gate slide. Following that event, decades of slowrebuilding continued through the 1980s and then changed to a decline. The 4-year movingaverage for adult returns per spawner hovered around 5 or 6 adult returns per spawner from thelate 1960s until the early 1990s, then declined steadily to less than 1 in 2009, before returning toabout 6 in 2010. (This was the overall pattern across all Fraser sockeye stocks – trends differedamong individual stocks.)The study looked at 52 sockeye stocks with decent time series of spawners and the resultingadult recruits, covering an area extending from Lake Washington in Seattle to Alaska (19 ofthese stocks were from the Fraser River). It looked at standard productivity indices (recruits perspawner; plus for the Fraser only, there were data for effective female spawners, which is a bettermeasure). The stationary Ricker model (it assumes a and b are stationary) was used to calculateannual residuals. The Larkin model was included as an alternative to the Ricker model toinvestigate possible delayed-density dependence. Both the Ricker and Larkin models remove28