Fish harvesting advice under climate change: A risk-equivalent empirical approach

for management actions in terms of fishery removals that would allow the stock to achieve the objective. The scope for changing the exploitation rate in relation to CC effects on stock production can be captured by risk equivalent contours for alternative fishing strategies (Fig 8). The case study here uses a maximum risk tolerance of 50% for the biomass objective. Therefore any risk contour smaller than 0.5 falls within the acceptable risk space associated with the objective (highlighted as the green area in Fig 8). The corresponding median temperature range over this acceptable risk space was about 1.5˚C-3.1˚C. At about 2.5˚C, a maximal exploitation rate of about 0.09 (or 9% of the population biomass of fish >40 cm), would achieve the biomass objective with a 50% probability over ten years. If median temperature increased to about 3˚C (i.e. a 0.5˚C increase from optimal), an exploitation rate of only about 3% would allow the objective to be achieved in 10 years at a 50% risk level. At median temperatures <1.5˚C and Fig 5. The projected production to biomass ratio (P/B) distribution of Gulf of St Lawrence given the four temperature scenarios (E) and generalised additive model model fit of P/B vs E and also by adding a random residual of that P/B vs E relationship to each future draw. The black line is status quo, i.e. the future is simply sampled from the past temperature distribution. The red line is the status quo temperature distribution with mean shift 0.5˚C warmer, the blue line the status quo temperature distribution shifted

0.5˚C colder and the green line is the status quo mean but with the standard deviation of the distribution increased by a factor of 1.5. The null model P/B (grey) is just the P/B distribution sampled without regard to the E variable. https://doi.org/10.1371/journal.pone.0239503.g005 PLOS ONE Climate-change conditioned risk-equivalent fisheries advice PLOS ONE | https://doi.org/10.1371/journal.pone.0239503 February 19, 2021 12 / 22