A trout fishing permit is not always required in the United States. There are certain states, however, where a permit is mandatory in order to fish for trout. In these states, a license can be obtained through the state department of wildlife or fisheries. The cost of a license varies depending on the state but is generally not expensive. There are a few things that fishermen should keep in mind when fishing for trout in states that require a permit. First, it is important to know what type of trout the state allows to be caught. Some states have specific regulations about the size and species of trout that can be caught. Second, permits are usually only good for a certain length of time, often no more than one year. It is important to renew the permit before it expires if you plan on continuing to fish for trout.