Rare-Event Simulation Techniques for Structured Fisheries Models

Depletion of fish stocks has a disastrous effect on the natural environment. One of the main goals in fisheries management is therefore to prevent the collapse of fish stocks. A key consideration is the impact of different harvest strategies and environmental noise on the likelihood of future stock collapse, or quasi-extinction. Motivated by this problem, we consider several rare-event simulation techniques to increase the speed and accuracy of projections of stock collapse. We consider both a one-dimensional structured fisheries model and a multidimensional age-structured fisheries model in applying our techniques. We observe that the way in which catch is modelled has a substantial impact on the likelihood of quasi-extinction. We reach the overall conclusion that the use of rare-event simulation techniques for structured fisheries models is worthwhile when the probability of quasi-extinction is on the order of 10^-2 or smaller.