Extended Data Fig. 2: Calculation of the LPI. | Nature

Extended Data Fig. 2: Calculation of the LPI.

From: Half a century of global decline in oceanic sharks and rays

Extended Data Fig. 2

a, Schematic example of constructing the observed (black) and projected (blue) LPI. First, year-to-year rates of change (yyrc) (dt) are averaged between species in the same region (for example, in region 1 (R1), species A with \({d}_{{{\rm{A}}}_{t}}\) and species B with \({d}_{{{\rm{B}}}_{t}}\) averaged in \({d}_{{{\rm{R}}1}_{t}}\)). In a second step, yyrc are averaged between regions 1, 2 and 3 to give the global yyrc. The observed LPI builds on the yyrc calculated from the estimated abundance index from the state–space population model. The projected LPI builds on the yyrc calculated from the estimated and projected abundance index from the state-space population model. Projections are from the last data point to 2020. b, Global LPI for oceanic sharks and rays estimated from 1970 to 2018 in black and extrapolated to 2020 in blue. The black and the thick blue lines denote, respectively, the mean of the estimated and extrapolated LPI. The white and thin blues lines denote, respectively, the 95% credible intervals of the estimated and extrapolated LPI and the grey lines denote each iteration of the estimated LPI. c, The annual percentage change was calculated from the posteriors of the estimated LPI (grey) and extrapolated LPI (blue) around the final-assessment year relative to the posteriors for 1970. Vertical bars for the 1970–2018 period denote the median of the estimated and extrapolated LPI.

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