The Truckee/Carson/Walker River watershed in northern Nevada is under an imminent threat of infestation by the New Zealand mud snail, an aquatic nuisance species with the potential to harm recreational fisheries. We combine a utility-theoretic system-demand model of recreational angling with a Bayesian econometric framework to provide estimates of trip and welfare losses under different types of regulatory control policies. We find that such losses can be substantial, warranting immediate investments in preemptive strategies via public outreach and awareness campaigns.