A model is introduced which demonstrates how vessel owners choose the optimal combination of trip length, gear used per day, and trips per season under open access and under various types of regulation. The nature of the model allows for an explicit analysis of current management tools (i.e., days at sea and trip limits), which is not possible using a traditional composite effort variable. The analysis describes the different margins along which inefficiencies can be introduced by traditional regulations and demonstrates how vessel operation and output will change in the short run. One new conclusion is that while binding regulations will always reduce profitability, in some cases they can actually increase annual output. In addition, the paper presents new insights concerning vessel operation under IQs and ITQs.