Mayflies dying out on legendary trout streams

British river fish suffer from decline in numbers of river flies

source: Michael McCarthy
Independent December 1 2001 p16

English rivers may have become cleaner in terms of having less sewage and industrial waste going into them, but river flies have dropped in number, which affects the fish that feed on them. Mayflies have especially been affected, and trout are fond of mayfly, which is why mayfly imitations are used by anglers. Fly numbers are estimated to have fallen by some two thirds since 1945, with much of this fall occurring since 1980. Intensive agriculture is thought to be the main cause, since there has been an increase in agricultural run-offs, which may include pesticides. Water companies also use river water, leaving less water to absorb pollutants, which become more concentrated.

The Wiltshire Fishery Association and the Environment Agency carried out a survey of southern England, using information from people fishing chalk trout streams, as well as owners of fisheries, and riverkeepers. These streams have traditionally been pure, with large fish and large numbers of flies, and mass mayfly hatchings, especially in late May and early June. The results of the survey indicate sharp drops for many mayfly species, and there is concern about what this implies for the state of English rivers.