Quantifying the tradeoff between precaution and yield in fishery reference points

A method using Monte Carlo simulations for estimating fishery reference points that accounts for parameter uncertainty is presented. Uncertainties in the input parameters of yield-per-recruit and stock-recruit analyses are propagated to estimate uncertainty in reference points such as FMSY. These uncertainties are used to evaluate the tradeoffs between the risks of overfishing and stock collapse, and the cost of reduced expected yield due to setting fishing mortality below FMSY. At fishing mortalities near FMSY, reduction in fishing mortality substantially decreases the probability of overfishing and stock collapse in exchange for slightly reduced expected yield. At lower fishing mortality rates, the marginal benefit (in terms of lessened risk of overfishing and stock collapse) from further reductions in fishing mortality is less, and the cost in forgone yield is greater. Less resilient “low steepness” stocks require additional precaution due to the risk of complete population collapse. Marine protected areas can also reduce risks of collapse, but at a higher cost in terms of expected yield than effort reduction. Implementation uncertainty (i.e. uncertainty in achieving a fishing mortality target) increases the risk of overfishing as well the loss of yield due to precaution, except at fishing mortalities near or above FMSY.