Fraser River sockeye salmon: data synthesis and cumulative impacts

Figure A4.2-2. Stock composition, scaled to a common axis for 5 different time periods. All five time periods in thisfigure reach 80% of the total recruits with only about 4 to 6 stocks.Decomposition of the dominant Fraser River sockeye stocks with data available illustrates thesizeable contrasts among cohorts resulting from the dominant four-year life history. The purposeof these graphs (Figure A4.2-3, A4.2-4, A4.2-5, A4.2-6) is simply to illustrate that there are infact substantial differences in stock composition among the cohorts. This may be a fairly obviousobservation to those with a scientific background in sockeye salmon; however, based on ourobservations of media coverage and other public fora it appears that this difference in stockcomposition among cohorts is often not recognized. In the public discourse, the poor 2009returns are often compared/contrasted with the high 2010 returns (these are the “comparisons” towhich we refer), without acknowledging that the situation is actually more complicated since notonly do the two years come from different generations/cycles, but the composition of each isdistinctly different. These graphs show quite clearly that 2009 versus 2010 is not a simple“apples-to-apples” comparison.229