River conservation, in its broadest sense, is now the concern of many.For some, such as the National Rivers Authority (NRA), it is a legalobligation, while for river users such as anglers it is a desirable goal butinvolves no statutory responsibilities. Public opinion polls show that thepopulace in general also feels it is important for rivers to be maintainedin a healthy state (Green & Tunstall in press), although they are notalways certain what it is they want, and their perception of whatconstitutes a "healthy" river may not coincide with that of an ecologist.Even nature conservationists have not always stated clearly theirconservation objectives for rivers, and their efforts have oftenconcentrated on "high profile" species such as otters, birds anddragonflies