Simulating enforcement and compliance as part of an evaluation framework for ballast water regulations

There is evidence that even if ballast water exchange is mandatory, without strong enforcement, compliance with regulations may be significantly lower than that reported by vessels. Meaningful evaluation of ballast water regulations should therefore take into account predicted violation rates in response to enforcement. To address this issue, I present a framework for simulating the violation-enforcement relationship, in which the output is the proportion of vessels that violate ballast water regulations. I apply the simulated violation results to a simple dose-response model to evaluate the relative importance of the relationship between violation rate and invasion rate. Results demonstrate that the benefit of improving (or even accurately quantifying) the violation rate is highly dependent on the biological uncertainty in the relationship between ballast water and establishment of invasive species. As for minimizing the violation rate, the best allocation of an enforcement budget is robust to the model assumptions explored here.