Fig. 9
Simulated mean estimates of (a) individual and (b) population fecundity (N of eggs) of Sognefjord veteran migrant brown trout, dependent upon selection of an individual’s maximum seaward migration distance (fjord habitat zone: inner-, mid- or outer-fjord) and their river of origin. Realised individual fecundity is estimated from the product of average expected size-specific fecundity \((\overline{{Fec }_{TL}}\)) and the maximum zone-specific survival rate \({S}_{maxZ}\) (\({S}_{maxZ}= \frac{{N}_{Surv}}{{N}_{Start}}\)). Realised population fecundity is estimated from the product of total (\(\overline{{Fec }_{TL}}\)) and mean survival (\({N}_{Surv}\)). Only individuals predicted to contribute to the spawning population are included in the realised estimates of egg numbers (from the initial population of 1000). Note: Boxplots present simulated mean values and 95% CI resulting from 100 iterations. Simulations were run on an annual basis for 2013 – 2015 conditions, and mean values across all years are presented (see Figure S8 for plots separated by year). Dependant on max zone reached, TL at end of growth season was estimated as\({TL}_{rep}={TLe}^{{g}_{SW2(maxZ)}* 0.5}\), where sea growth was estimated from 2nd sea age specific growth (\({g}_{SW2}\)). Size-specific estimates of fecundity (\(\overline{{Fec }_{TL}}\)) were generated according to\({Fec}_{TL}={e}^{-4.03+2.74* {TL}_{Rep}}\). Only individuals contributing to the spawning population (\({TL}_{Rep}\)> 35 cm and retuned to freshwater during the period WoY 37 – 52), were included in the estimates of realised fecundity. Table 4b states mean values of realised individual and population fecundity for each study population