Fraser River sockeye salmon: data synthesis and cumulative impacts

(Fennell), which is equivalent to annual declines on the R/S scale of: ~1.7% to 6.5% since~1950.Table A4.1-2. Summary of stocks where a single trend line was more appropriate. The estimated slope of the line isshown along with the associated test statistic and p-value (significant p-values are indicated by a *).Arrows indicate the direction of the trend.Stock Slope (b1) Test statisticfor b1p-value 23Trend overentire timeseriesBirkenhead -0.035 -4.059 < 0.001* ↓Bowron -0.017 -2.520 0.015* ↓Fennell -0.067 -5.374 < 0.001* ↓Gates -0.050 -4.071 < 0.001* ↓Harrison 0.012 0.978 0.332 ↔L.Shuswap -0.007 -0.889 0.378 ↔L.Stuart -0.027 -2.464 0.017* ↓Nadina -0.028 -1.849 0.074↓ (weakevidence)↓(weakevidence)Portage -0.021 -1.935 0.059Raft -0.005 -0.690 0.493 ↔Scotch -0.048 -3.346 0.002* ↓Seymour -0.023 -3.073 0.003* ↓Weaver -0.004 -0.294 0.770 ↔A4.2 Analyses of Stock CompositionThree time periods follow a very similar pattern both in terms of the shape of the concentrationprofile and the average number of recruits (between 4 & 6 million), these include the two earliesttime periods: 1948-1959, 1960-1971, and the most recent one: 1996-2006 (Figure A4.2-1). Theother two time periods have a similar shape but the average number of recruits was substantiallyhigher: 1972-1983 (~8 million) and 1984-1995 (~11 million). When the y-axis was scaled to 1to represent the cumulative proportion of total recruits, we see that the shape of the curves arevery similar across all time periods with 80% of the total recruits composed of only 4-6 stocksout of the 19 evaluated (Figure A4.2-2). The primary reason for plotting these figures was todetermine if the portfolio balance had changed over time and if that might be a potentialexplanation for the long-term decline in Fraser River sockeye productivity. While the totalnumber of recruits has varied substantially over time, the shape of the concentration profile hasnot. Contrary to our expectation, there has not been a substantial change in the “portfolio23 P-value is associated with the null hypothesis that the slope (b1) = 0. A small p-value (i.e.,