We work closely with angling tenants, angling clubs and associations and national organisations to promote good practice in the management of our fisheries. Visiting anglers can make an important contribution, for the long-term benefit of their sport and of the environment generally, by following the rules for each fishery and the general rules and codes of conduct.

We place a high conservation value on waters with both varied and rare fish species, and waters which have been relatively unaffected by human activity. Other important aspects are good water quality, the variety of aquatic plants and invertebrates, healthy populations of newts, toads and frogs, the presence of scarce birds and mammals such as otter and water vole, and the quality of the bankside habitat. Sometimes even the absence of fish is of interest, because such waters are often of particular value for amphibians and invertebrates.

Fishery Management Plans are being prepared for most sites. These set out specific objectives including, wherever practicable, maintaining good water quality, controlling sediments (if necessary by changing land-use practices), fostering native and diverse aquatic vegetation, and resisting the use of mechanical cutting and herbicides to control vegetation. Bankside trees and the woody debris they create are important; excessive shade can be reduced by coppicing or pollarding.

To achieve this it is often necessary for the Trust, and others with an interest in pollution-free waters, to try to influence what happens in water catchment areas beyond our direct control.

High fish densities can have a damaging effect on the balance of freshwater ecosystems. Too many fish can turn clear, still waters with plenty of submerged plants into turbid waters with extensive blooms of algae, leading to slower fish growth rates and a higher incidence of disease.

Equally, heavily stocked waters are often associated with large numbers of anglers, which can cause bank erosion, damage to vegetation and the introduction of large amounts of bait. Introductions can also cause disease as well as harmful behavioural and breeding interaction with wild fish.

Although it has been claimed that coarse fish cause a reduction in game species, the Trust is not convinced by the evidence from the small amount of research that has been done. Moreover, large-scale removal of coarse fish and grayling may lead to an increase in predation of trout and salmon by pike and fish-eating birds. Equally, removal of large pike, which eat many small pike, increases both the numbers of small pike and their predation of other species.