The behavior of fishermen is often far more complicated than assumed by fisheries managers. Those concerned with the Maine lobster (i.e., American lobster Homarus americanus, hereafter "lobster") fishery have long favored a cap on the number of traps each license holder can use. Fishermen favor trap limits primarily to cut costs and limit congestion, and managers believe such limits will help reduce fishing effort. Yet when trap limits were imposed by the legislature and the lobster zone councils between 1995 and 1998, the number of traps fished in Maine waters increased greatly. A survey of half the lobster license holders carried out in the summer and fall of 1998 revealed that the response of fishermen to trap limits was highly differential. Some fishermen reduced, but more increased, the number of traps they fished. A complicated set of variables influenced those decisions concerning trap numbers, including the regulatory environment, age and characteristics of the fishermen, relative economic opportunities, and reference group behavior. One of the assumptions running through the literature on fisheries management is that fishermen are homogenous and respond in similar ways to management initiatives. In fact, if we can judge by the data from the Maine lobster fishery, the response of fishermen to a management initiative can be quite diverse, and license holders may respond to a wide variety of social and economic factors in ways that confound the goals of management. This study points out that the effects of management cannot be ascertained unless we have an accurate and relatively sophisticated understanding of the myriad factors motivating the decisions of the fishermen.