Developing and implementing total maximum daily loads (TMDLs) is a costly and controversial process. However, there are many potential benefits, such as improvements to commercial fisheries. A two-stage model is developed to estimate the benefits of the Chesapeake Bay TMDL on the Maryland blue crab fishery. In the first stage, a bio-economic model links water quality to stock and harvest and various hypotheses on this link are tested. In the second stage, a model of fisherman behavior links the effects of changes in water quality on stock and harvest to fisherman behavior, such as fishing, location, and effort decisions. A number of simulations are then run to predict the effects of the TMDL on the Maryland blue crab fishery. The simulations predict that the TMDL is likely to have a small, if not insignificant, effect on the fishery. This result is in part explained by the fact that the current level of water quality in the Chesapeake Bay is suitable for the blue crabs.