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Fraser River sockeye salmon: data synthesis and cumulative impacts

Fraser River sockeye salmon: data synthesis and cumulative impacts

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Appendix 4. Quantitative ResultsA4.1 Trend <strong>and</strong> Change Point Analysis of Productivity by StockTrend analyses of <strong>sockeye</strong> productivity (i.e., ln(R/S)) over time found that 6 of the 19 <strong>Fraser</strong>stocks were better fit by the piece-wise regression model (allowing for 2 different trends over thetime-series) than a single straight line regression over time (Table A4.1-1). The recent trends for5 of these stocks (excluding Pitt) ranged from: -0.050 to -0.141, which is equivalent to annualdeclines on the R/S scale of: ~5% (Early Stuart) to 13% 22 (Quesnel). The earliest change-pointoccurred in 1965 (Early Stuart) <strong>and</strong> the latest occurred in 1988 (Chilko). Pitt is reportedseparately as we are not sure how reflective this stock is of other wild <strong>Fraser</strong> stocks due to itshigh hatchery influence. The recent trend in Pitt was -0.466, which corresponds to an averageannual decline of ~35% since 1999. Despite having only 5 years of <strong>data</strong> to estimate the post1999 trend, the p-value was

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