The increase in popularity of ‘big game’ type angling in the UK has lead to a proliferation of waters stocked with non-native species. Many introductions have been illegal and the potentially irreversible ecological consequences are yet to be realised. Some case histories are presented and show the potential impacts of these species to involve the effects of predation, competition, disease, hybridisation and habitat degradation. Responding to anglers’ demands while controlling any illegal spread of non-native fish in the wild is a major challenge. The legislation that governs the movement of fish into and within England and Wales is shared between the Environment Agency and other Government organisations, a situation that engenders significant management difficulties and enables less scrupulous movers of fish to exploit any weaknesses in the enforcement system. The problem is being addressed in a number of ways. A fully coordinated approach to the regulation of fish movements is being facilitated by a new database and the Environment Agency has reviewed the policies through which it regulates movements of fish into the wild. The guiding principle is that fish introductions should not jeopardise the well being of naturally established ecosystems, i.e. there should be no detriment to the donor or recipient fisheries, or to the fish being introduced. This approach was endorsed by a recent Government review of fisheries legislation that recommended strengthening controls over inappropriate movements of fish.